Re: [Ecn-sane] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

Re: [Ecn-sane] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Dave Taht]

[-- Attachment #1: Type: text/plain, Size: 8673 bytes --]

Bufferbloat.net's ecn-sane working group members have a co-ordinated
response to your efforts brewing but it's not ready yet. We have a
worldwide team of linux and freebsd developers co-ordinating on landing
code for our competing proposal "Some Congestion Experienced", which we
submitted to tsvwg last sunday.

That draft is under continuous revision, here:

https://github.com/dtaht/bufferbloat-rfcs/blob/master/sce/draft-morton-taht-tsvwg-sce.txt

Our Linux and FreeBSD team is also flying into prague for SCE presentations
at netdevconf and ietf.

Some background to this: after the L4S/TCP Prague/and dualpi experiments
appeared stalled out indefinitely in the IETF, and with our own frustration
with IETF processes, bufferbloat.net project members publicly formed our
own working group to look into the problems with ecn, back in august of
last year.

Its charter is here: https://www.bufferbloat.net/projects/ecn-sane/wiki/

We were unaware, until last month, that the cable industry had 16 months
back gone and formed its own private working group also, and was intending
to turn the tcp prague/l4s/dualpi IETF "experiments" into an actual DOCSIS
standard.

Our SCE proposal appears to be backward compatible with the existing
10s-100s of millions of ecn-enabled fq_codel[1] and sch_cake[2]
deployments, and doesn't require any changes to any RFC3168 tcps (or any
tcp-friendly congestion control) at all in order to basically work.
tcp-prague is subtly incompatible with that, and dualpi, more so. Our
proposal is different also, it proposes some receiver side changes in order
to get the full benefit of SCE while remaining backward compatible with the
existing meaning of the CE codepoint.

In either case, either approach essentially permanently redefines the ECT_1
codepoint incompatibly, once and for all, and for all time. This is a final
battle over the meaning of a single bit in IP, and I expect the debates to
be as difficult as the ones described in
https://www.ietf.org/rfc/ien/ien137.txt - I would really, really, really
prefer that they stay technical and not veer into politics, but I have
little hope for that.

The members of the ecn-sane working group are delighted to finally hear
that running code for tcp-prague might land this ietf, and look forward to
finally testing the whole l4s/tcpprague/dualpi architecture in conjunction
with the flent.org 's and irtt's exhaustive suite of tests and servers in
the cloud in the coming months, both against our existing, deployed,
fq_codel, fq_pie, cake and pie derived solutions and our new SCE proposal.
We hope to finally be able to write new tests for flent in particular, that
can show tcpprague off in the ways that are important to those developing
it. Flent has some basic dctcp tests, but nothing that can get down below a
20ms sample rate on modern hardware. (currently. It's easy to add tests,
flent is written in python)

We also hope that more test tools and implementations in ns2 and ns3 show
up for tcpprauge  and dualpi show up soon also, from members of those
projects.

Note: sunday's dual-pi linux submission was kicked back from the linux
networking developers due to some technical and legal problems with linux
net-next HEAD ( https://patchwork.ozlabs.org/patch/1054521/  ) , and I do
hope that a corrected version lands soon, so we can safely test it with
current versions of OpenWrt, etc.

Finally, running code. Will we find consensus?

Thx!


[1] https://tools.ietf.org/html/rfc8290
[2] sch_cake was available for 3 years out of tree and was mainlined last
august, in linux 4.19. It is partially described by "Piece of CAKE: A
Comprehensive Queue Management Solution for Home Gateways" "
https://arxiv.org/pdf/1804.07617.pdf

A second paper describing its fq_codel-derived "cobalt" AQM algorithm is
awaiting publication in a peer reviewed journal. It has been part of
openwrt and the related sqm-scripts for many years and is widely deployed
on multiple commercial products, such as those from eero and evenroute.

Cake has a docsis specific mode which we longed for cablelabs to evaluate.


On Fri, Mar 15, 2019 at 2:33 AM Bob Briscoe <ietf@bobbriscoe.net> wrote:

> Forwarding to tcpm & iccrg - apologies if you were already on one of the
> lists that received this.
>
> Olivier has been working hard on integrating the pieces of a Linux
> implementation of TCP Prague, and is close to having a version ported
> against the tip of the Linux mainline tree. This is his request for more
> people to get involved.
>
>
> Bob
>
>
> -------- Forwarded Message --------
> Subject: [tcpPrague] Implementation and experimentation of TCP Prague/L4S
> hackaton at IETF104
> Date: Wed, 6 Mar 2019 10:26:05 +0000
> From: Tilmans, Olivier (Nokia - BE/Antwerp)
> <olivier.tilmans@nokia-bell-labs.com>
> <olivier.tilmans@nokia-bell-labs.com>
> To: hackathon@ietf.org <hackathon@ietf.org> <hackathon@ietf.org>,
> tcpprague@ietf.org <tcpprague@ietf.org> <tcpprague@ietf.org>
> CC: dlebrun@google.com <dlebrun@google.com> <dlebrun@google.com>, Joakim
> Misund <joakim.misund@gmail.com> <joakim.misund@gmail.com>, Bob Briscoe
> <research@bobbriscoe.net> <research@bobbriscoe.net>, Quentin De Coninck
> <quentin.deconinck@uclouvain.be> <quentin.deconinck@uclouvain.be>,
> François Michel <francois.michel@uclouvain.be>
> <francois.michel@uclouvain.be>, Mirja Kuehlewind
> <mirja.kuehlewind@tik.ee.ethz.ch> <mirja.kuehlewind@tik.ee.ethz.ch>,
> Maxime Piraux <maxime.piraux@uclouvain.be> <maxime.piraux@uclouvain.be>,
> Olga Albisser <olga@albisser.org> <olga@albisser.org>, Fabien Duchêne
> <fabien.duchene@uclouvain.be> <fabien.duchene@uclouvain.be>, De Schepper,
> Koen (Nokia - BE/Antwerp) <koen.de_schepper@nokia-bell-labs.com>
> <koen.de_schepper@nokia-bell-labs.com>
>
> Hi all,
>
> We'll be working on the "TCP Prague" congestion control/L4S architecture
> during the IETF-104 hackaton.
> This topics aims at accelerating the work that started during the IETF93
> (coincidentally also in Prague), in order to get TCP Prague to an 'usable'
> state—i.e., meet the safety requirements and have supporting materials
> (e.g., VMs, labs) to let people experiment with it. Depending on people's
> interest, prototyping something similar for QUIC is another possible output.
>
> Details and links to resources/supporting drafts are available at
> https://trac.ietf.org/trac/ietf/meeting/wiki/104hackathon#tcp-prague and
> copied below.
> Additionally, few topics will presented during netdev 0x13 the week before.
>
> See you in Prague.
>
> Best,
> Olivier
>
>
> Implementation and experimentation of TCP Prague/L4S
>
> * Champion
> * Olivier Tilmans <olivier.tilmans at nokia-bell-labs.com>
> * Projects
> * Prototype the "TCP Prague" congestion control on Linux
> * Finalize the implementation of accurate ECN (draft conformance), and
> port it on Linux v5.x * Build tooling around L4S to let people experiment
> with the technology (e.g., virtual machine, or mininet labs)
> * Work towards "QUIC Prague"
> * Resources
> * TCP Prague
> * Repository — ​https://github.com/L4STeam/tcp-prague
> * Requirements — ​
> https://tools.ietf.org/html/draft-ietf-tsvwg-ecn-l4s-id-05#page-21
> * Upcoming netdev talk —
> https://netdevconf.org/0x13/session.html?talk-tcp-prague-l4s
> * Accurate ECN
> * Specs — ​https://tools.ietf.org/html/draft-ietf-tcpm-accurate-ecn-07
> * Implementation for Linux v4.17 — ​https://github.com/mirjak/linux-accecn
> * Past netdev talk —
> https://www.netdevconf.org/2.2/session.html?kuhlewind-accecn-talk
> * Paced Chirping * Repository — ​
> https://github.com/JoakimMisund/PacedChirping
> * Upcoming netdev talk —
> https://netdevconf.org/0x13/session.html?talk-chirp
> * L4S architecture
> * Specs — ​https://tools.ietf.org/html/draft-ietf-tsvwg-l4s-arch-03
> * DualPI2 AQM
> * Specs — ​
> https://tools.ietf.org/html/draft-ietf-tsvwg-aqm-dualq-coupled-08
> * Repository — ​https://github.com/L4STeam/sch_dualpi2_upstream
> * Upcoming netdev talk —
> https://netdevconf.org/0x13/session.html?talk-DUALPI2-AQM
> * RITE Project — ​https://riteproject.eu/dctth/#code
> _______________________________________________
> tcpPrague mailing list
> tcpPrague@ietf.org
> https://www.ietf.org/mailman/listinfo/tcpprague
> _______________________________________________
> iccrg mailing list
> iccrg@irtf.org
> https://www.irtf.org/mailman/listinfo/iccrg
>


-- 

Dave Täht
CTO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-831-205-9740

[-- Attachment #2: Type: text/html, Size: 16938 bytes --]

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Dave Taht]

I would really prefer to move this discussion to the ecn-sane mailing
list, as IMHO, ecn is generally such a tiny thing needed for good
congestion control compared to better transports like pacing + bbr,
and things like bql, fq, and aqm using drop.

I'm going to keep cc-ing that list in the hope that we can keep better
track of the discussion here.

On Fri, Mar 15, 2019 at 6:01 AM Sebastian Moeller <moeller0@gmx.de> wrote:
>
> Hi Dave,
>
> I pruned the CC list as I am out of my league here and want to restrict the radius of my embarrassment to those that already know my level of incompetence before hand.

IMHO, your work on educating the OpenWrt community over the years on
how to use sqm, makes you much more than "only a grasshopper". You
have a firm grip on what can be achieved in the real world.

>
> That said, having read through the L4S architecture description and the related appendices of draft-ietf-tsvwg-ecn-l4s-id-05 I came to the conclusion, that this is a mess.

I am so glad someone other than I has now read it.

> The L4S project proposes a really wide-ranging change of basically the internet (but allow a concurrent operation with legacy probably to cater to the fact that an internet-wide flag-day seems daunting to organize). But then they chicken out when figuring out how to differentiate between their new and the old by proposing to use ECT(1) for a purpose outside of its nominal purpose namely explicit congestion notification, why not think bolder? If the plan is to change everything the feasibility can not hinge upon the ability to re-using one old legacy bit, can it...
> Conceptually it seems much cleaner to use ECT(1) for congestion notification directly (there are already proposals out there and SCE just added another fully back-ward compatible one) and find another way to mark l4s traffic, sure that is going to be hard and inconvenient, but if you set out to change the internet that is par for the course.
> IMHO they would do more good if they actually fought for a better use of the 6 DSCP bits instead. (say by splitting into two groups of 3 bits, one group for reduced diffserv and one group for new features, that would even

The existing diffserv deployment is a failure. I have another ID
cooking that suggests a better way, going forward, to use them, but I
do not feel at this time it would be useful to present. One big battle
at a time. That ID is very simple, it basically proposes that all
diffserv codepoints be passed through ISPs and transit providers
unchanged, and if any given codepoint must be changed, the only
permissible change is to 0 (BE), and MUST be not be remarked to
anything else, especially not CS1.

>allow for concurrent use of the inevitable L5S and L6S ;) ). Especially since as far as I can understand l4s actually would like to have a more gradual congestion information stream than classic ECN, and since they need to modify DCTCP anyway to make it save for the wider internet, replacing its ECN response should be well inside the scope of work they already have on their list.

Next up for sce was going to be to find if dctcp could be modified to
use it. Also, bittorrent.

> If I sound a bit miffed, it is because after reading https://tools.ietf.org/html/draft-ietf-tsvwg-l4s-arch-03 I do not have the feeling they are trying to build abetter internet, but rather that they are building an internet where I can be a better "product" and customer of newfangled services, and I do not look forward to such a facebooky future with much enthusiasm.

I have rigorously tried to keep the network neutrality debate out of
this. dualpi is just another aqm that needs the same thorough
technical and public evaluation done to it that pie, codel, fq_codel
were subjected to.The use of ect_1 in dualpi for it is nuts IMHO, and
I'd vastly prefer that another L4S codepoint be added to make it work,
but any attempt to do so would also require industry consolidation on
that ID and that would be distracting at this time.

It appears, also, ironically, (I have confirmation from several
sources now) that cake, fq_codel and dualpi are now illegal for an ISP
to use in their provided equipment under california law. The idea of
one day having to appear in court to defend our key algorithms reminds
me of the famous john fogerty case where he demonstrated how blues
music was made.

I wish I knew a lawyer willing to take on "bufferbloat.net vs the
state of california", though, as it may come down to that.

I blew up on this part of the issue here:
http://blog.cerowrt.org/post/net_neutrality_customers/
>
> I hope that the discussion in Prague go well and a compromise/consense can be hashed out as I see different implementations duking it out here, but the overall goal of the competitors seems quite compatible, improving the internet by focussing on latency.
>
> Best Regards
>         Sebastian
>
> > On Mar 15, 2019, at 11:46, Dave Taht <dave.taht@gmail.com> wrote:
> >
> > Bufferbloat.net's ecn-sane working group members have a co-ordinated response to your efforts brewing but it's not ready yet. We have a worldwide team of linux and freebsd developers co-ordinating on landing code for our competing proposal "Some Congestion Experienced", which we submitted to tsvwg last sunday.
> >
> > That draft is under continuous revision, here:
> >
> > https://github.com/dtaht/bufferbloat-rfcs/blob/master/sce/draft-morton-taht-tsvwg-sce.txt
> >
> > Our Linux and FreeBSD team is also flying into prague for SCE presentations at netdevconf and ietf.
> >
> > Some background to this: after the L4S/TCP Prague/and dualpi experiments appeared stalled out indefinitely in the IETF, and with our own frustration with IETF processes, bufferbloat.net project members publicly formed our own working group to look into the problems with ecn, back in august of last year.
> >
> > Its charter is here: https://www.bufferbloat.net/projects/ecn-sane/wiki/
> >
> > We were unaware, until last month, that the cable industry had 16 months back gone and formed its own private working group also, and was intending to turn the tcp prague/l4s/dualpi IETF "experiments" into an actual DOCSIS standard.
> >
> > Our SCE proposal appears to be backward compatible with the existing 10s-100s of millions of ecn-enabled fq_codel[1] and sch_cake[2] deployments, and doesn't require any changes to any RFC3168 tcps (or any tcp-friendly congestion control) at all in order to basically work. tcp-prague is subtly incompatible with that, and dualpi, more so. Our proposal is different also, it proposes some receiver side changes in order to get the full benefit of SCE while remaining backward compatible with the existing meaning of the CE codepoint.
> >
> > In either case, either approach essentially permanently redefines the ECT_1 codepoint incompatibly, once and for all, and for all time. This is a final battle over the meaning of a single bit in IP, and I expect the debates to be as difficult as the ones described in https://www.ietf.org/rfc/ien/ien137.txt - I would really, really, really prefer that they stay technical and not veer into politics, but I have little hope for that.
> >
> > The members of the ecn-sane working group are delighted to finally hear that running code for tcp-prague might land this ietf, and look forward to finally testing the whole l4s/tcpprague/dualpi architecture in conjunction with the flent.org 's and irtt's exhaustive suite of tests and servers in the cloud in the coming months, both against our existing, deployed, fq_codel, fq_pie, cake and pie derived solutions and our new SCE proposal. We hope to finally be able to write new tests for flent in particular, that can show tcpprague off in the ways that are important to those developing it. Flent has some basic dctcp tests, but nothing that can get down below a 20ms sample rate on modern hardware. (currently. It's easy to add tests, flent is written in python)
> >
> > We also hope that more test tools and implementations in ns2 and ns3 show up for tcpprauge  and dualpi show up soon also, from members of those projects.
> >
> > Note: sunday's dual-pi linux submission was kicked back from the linux networking developers due to some technical and legal problems with linux net-next HEAD ( https://patchwork.ozlabs.org/patch/1054521/  ) , and I do hope that a corrected version lands soon, so we can safely test it with current versions of OpenWrt, etc.
> >
> > Finally, running code. Will we find consensus?
> >
> > Thx!
> >
> >
> > [1] https://tools.ietf.org/html/rfc8290
> > [2] sch_cake was available for 3 years out of tree and was mainlined last august, in linux 4.19. It is partially described by "Piece of CAKE: A Comprehensive Queue Management Solution for Home Gateways" "https://arxiv.org/pdf/1804.07617.pdf
> >
> > A second paper describing its fq_codel-derived "cobalt" AQM algorithm is awaiting publication in a peer reviewed journal. It has been part of openwrt and the related sqm-scripts for many years and is widely deployed on multiple commercial products, such as those from eero and evenroute.
> >
> > Cake has a docsis specific mode which we longed for cablelabs to evaluate.
> >
> >
> > On Fri, Mar 15, 2019 at 2:33 AM Bob Briscoe <ietf@bobbriscoe.net> wrote:
> > Forwarding to tcpm & iccrg - apologies if you were already on one of the lists that received this.
> >
> > Olivier has been working hard on integrating the pieces of a Linux implementation of TCP Prague, and is close to having a version ported against the tip of the Linux mainline tree. This is his request for more people to get involved.
> >
> >
> > Bob
> >
> >
> > -------- Forwarded Message --------
> > Subject:      [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104
> > Date: Wed, 6 Mar 2019 10:26:05 +0000
> > From: Tilmans, Olivier (Nokia - BE/Antwerp) <olivier.tilmans@nokia-bell-labs.com>
> > To:   hackathon@ietf.org <hackathon@ietf.org>, tcpprague@ietf.org <tcpprague@ietf.org>
> > CC:   dlebrun@google.com <dlebrun@google.com>, Joakim Misund <joakim.misund@gmail.com>, Bob Briscoe <research@bobbriscoe.net>, Quentin De Coninck <quentin.deconinck@uclouvain.be>, François Michel <francois.michel@uclouvain.be>, Mirja Kuehlewind <mirja.kuehlewind@tik.ee.ethz.ch>, Maxime Piraux <maxime.piraux@uclouvain.be>, Olga Albisser <olga@albisser.org>, Fabien Duchêne <fabien.duchene@uclouvain.be>, De Schepper, Koen (Nokia - BE/Antwerp) <koen.de_schepper@nokia-bell-labs.com>
> >
> > Hi all,
> >
> > We'll be working on the "TCP Prague" congestion control/L4S architecture during the IETF-104 hackaton.
> > This topics aims at accelerating the work that started during the IETF93 (coincidentally also in Prague), in order to get TCP Prague to an 'usable' state—i.e., meet the safety requirements and have supporting materials (e.g., VMs, labs) to let people experiment with it. Depending on people's interest, prototyping something similar for QUIC is another possible output.
> >
> > Details and links to resources/supporting drafts are available at https://trac.ietf.org/trac/ietf/meeting/wiki/104hackathon#tcp-prague and copied below.
> > Additionally, few topics will presented during netdev 0x13 the week before.
> >
> > See you in Prague.
> >
> > Best,
> > Olivier
> >
> >
> > Implementation and experimentation of TCP Prague/L4S
> >
> > * Champion
> > * Olivier Tilmans <olivier.tilmans at nokia-bell-labs.com>
> > * Projects
> > * Prototype the "TCP Prague" congestion control on Linux
> > * Finalize the implementation of accurate ECN (draft conformance), and port it on Linux v5.x * Build tooling around L4S to let people experiment with the technology (e.g., virtual machine, or mininet labs)
> > * Work towards "QUIC Prague"
> > * Resources
> > * TCP Prague
> > * Repository — https://github.com/L4STeam/tcp-prague
> > * Requirements — https://tools.ietf.org/html/draft-ietf-tsvwg-ecn-l4s-id-05#page-21
> > * Upcoming netdev talk — https://netdevconf.org/0x13/session.html?talk-tcp-prague-l4s
> > * Accurate ECN
> > * Specs — https://tools.ietf.org/html/draft-ietf-tcpm-accurate-ecn-07
> > * Implementation for Linux v4.17 — https://github.com/mirjak/linux-accecn
> > * Past netdev talk — https://www.netdevconf.org/2.2/session.html?kuhlewind-accecn-talk
> > * Paced Chirping * Repository — https://github.com/JoakimMisund/PacedChirping
> > * Upcoming netdev talk — https://netdevconf.org/0x13/session.html?talk-chirp
> > * L4S architecture
> > * Specs — https://tools.ietf.org/html/draft-ietf-tsvwg-l4s-arch-03
> > * DualPI2 AQM
> > * Specs — https://tools.ietf.org/html/draft-ietf-tsvwg-aqm-dualq-coupled-08
> > * Repository — https://github.com/L4STeam/sch_dualpi2_upstream
> > * Upcoming netdev talk — https://netdevconf.org/0x13/session.html?talk-DUALPI2-AQM
> > * RITE Project — https://riteproject.eu/dctth/#code
> > _______________________________________________
> > tcpPrague mailing list
> > tcpPrague@ietf.org
> > https://www.ietf.org/mailman/listinfo/tcpprague
> > _______________________________________________
> > iccrg mailing list
> > iccrg@irtf.org
> > https://www.irtf.org/mailman/listinfo/iccrg
> >
> >
> > --
> >
> > Dave Täht
> > CTO, TekLibre, LLC
> > http://www.teklibre.com
> > Tel: 1-831-205-9740
> > _______________________________________________
> > Bloat mailing list
> > Bloat@lists.bufferbloat.net
> > https://lists.bufferbloat.net/listinfo/bloat
>


--

Dave Täht
CTO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-831-205-9740

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Sebastian Moeller]

Hi Dave,


> On Mar 15, 2019, at 15:06, Dave Taht <dave.taht@gmail.com> wrote:
> 
> I would really prefer to move this discussion to the ecn-sane mailing
> list, as IMHO, ecn is generally such a tiny thing needed for good
> congestion control compared to better transports like pacing + bbr,
> and things like bql, fq, and aqm using drop.
> 
> I'm going to keep cc-ing that list in the hope that we can keep better
> track of the discussion here.

	Ah, sure, I basically wanted to avoid annoying the ietf lists as I feel out of place there, having only had a cursory read of the relevant RFCs.


> 
> On Fri, Mar 15, 2019 at 6:01 AM Sebastian Moeller <moeller0@gmx.de> wrote:
>> 
>> Hi Dave,
>> 
>> I pruned the CC list as I am out of my league here and want to restrict the radius of my embarrassment to those that already know my level of incompetence before hand.
> 
> IMHO, your work on educating the OpenWrt community over the years on
> how to use sqm, makes you much more than "only a grasshopper". You
> have a firm grip on what can be achieved in the real world.
> 
>> 
>> That said, having read through the L4S architecture description and the related appendices of draft-ietf-tsvwg-ecn-l4s-id-05 I came to the conclusion, that this is a mess.
> 
> I am so glad someone other than I has now read it.
> 
>> The L4S project proposes a really wide-ranging change of basically the internet (but allow a concurrent operation with legacy probably to cater to the fact that an internet-wide flag-day seems daunting to organize). But then they chicken out when figuring out how to differentiate between their new and the old by proposing to use ECT(1) for a purpose outside of its nominal purpose namely explicit congestion notification, why not think bolder? If the plan is to change everything the feasibility can not hinge upon the ability to re-using one old legacy bit, can it...
>> Conceptually it seems much cleaner to use ECT(1) for congestion notification directly (there are already proposals out there and SCE just added another fully back-ward compatible one) and find another way to mark l4s traffic, sure that is going to be hard and inconvenient, but if you set out to change the internet that is par for the course.
>> IMHO they would do more good if they actually fought for a better use of the 6 DSCP bits instead. (say by splitting into two groups of 3 bits, one group for reduced diffserv and one group for new features, that would even
> 
> The existing diffserv deployment is a failure.

	Which is a shame, but one RFC's failure is another one's opportunity.


> I have another ID
> cooking that suggests a better way, going forward, to use them, but I
> do not feel at this time it would be useful to present. One big battle
> at a time.

:)

> That ID is very simple, it basically proposes that all
> diffserv codepoints be passed through ISPs and transit providers
> unchanged, and if any given codepoint must be changed, the only
> permissible change is to 0 (BE), and MUST be not be remarked to
> anything else, especially not CS1.

	I like the simplicity, but I also like the split into two groups of 3 bits, say "active bit pattern" (for transport purposes) and "intenden bit pattern" for the sender to transmit intent, which than can be conveyed lossless to the receiver; my gut feeling is that throwing the transport people a bone here might work better, as in the end they are the one that will carry the "burden" of the change. IMHO this has the additional advantage that it will make "tabula rasa" of the existing distict set of bit patterns used in the real world. Which in turn probably is this ideas downfall...


> 
>> allow for concurrent use of the inevitable L5S and L6S ;) ). Especially since as far as I can understand l4s actually would like to have a more gradual congestion information stream than classic ECN, and since they need to modify DCTCP anyway to make it save for the wider internet, replacing its ECN response should be well inside the scope of work they already have on their list.
> 
> Next up for sce was going to be to find if dctcp could be modified to
> use it. Also, bittorrent.

	YES! I endorse this message.

> 
>> If I sound a bit miffed, it is because after reading https://tools.ietf.org/html/draft-ietf-tsvwg-l4s-arch-03 I do not have the feeling they are trying to build abetter internet, but rather that they are building an internet where I can be a better "product" and customer of newfangled services, and I do not look forward to such a facebooky future with much enthusiasm.
> 
> I have rigorously tried to keep the network neutrality debate out of
> this.

	And I really do not want to start this here, as I agree that this is about a technical question. That said, I had hoped more out of the l4s promises from an end-user perspective. Then again, it if this is going to happen it needs the ISPs buy-in so it might be politically wise to emphasize the advantages for ISPs.


> dualpi is just another aqm that needs the same thorough
> technical and public evaluation done to it that pie, codel, fq_codel
> were subjected to.

+1, I note that the main argument against fq is "we can do it with two" without a convincing argument why two is better than the few 100s you realistically will never need for fq even on an busy core router.

> The use of ect_1 in dualpi for it is nuts IMHO,

	At least it is unclean...

> and
> I'd vastly prefer that another L4S codepoint be added to make it work,
> but any attempt to do so would also require industry consolidation on
> that ID and that would be distracting at this time.

	But as I said, L4S aims to change everything so why stop there ;)

> 
> It appears, also, ironically, (I have confirmation from several
> sources now) that cake, fq_codel and dualpi are now illegal for an ISP
> to use in their provided equipment under california law.

	I will happily look at specific sections of code if pointed to, but I will not actively search for. At least the European net neutrality rules do not make any of these illegal, as the rules allow for traffic management (and special services at extra cost as long as these are not built be restricting the best-effort net, no idea how that should be poiced) (and in the end the rules only apply for ISPs in one's own network one can DPI to a far greater extent if one is such inclined).


> The idea of
> one day having to appear in court to defend our key algorithms reminds
> me of the famous john fogerty case where he demonstrated how blues
> music was made.

	I see a nice art-house movie coming up.


> 
> I wish I knew a lawyer willing to take on "bufferbloat.net vs the
> state of california", though, as it may come down to that.
> 
> I blew up on this part of the issue here:
> http://blog.cerowrt.org/post/net_neutrality_customers/

	I read that, but it does not reflect to well on the situation this side of the pond. We had situations where ISPs worked hard (but without success) to switch from their flat-rate access to introduce volume caps, that served a dual purpose, a) extracting more revenue from customers and b) allowing to make "zero-rating" deals with content-providers (which in the end are also payed for by the end-users, indirectly). Sure, this is all normal in business, but that does not necessarily mean that I do need to like being a pawn in a business transaction between global corporations. (I consider this to be at least somewhat related to the net neutrality debate).

Best Regards
	Sebastian


>> 
>> I hope that the discussion in Prague go well and a compromise/consense can be hashed out as I see different implementations duking it out here, but the overall goal of the competitors seems quite compatible, improving the internet by focussing on latency.
>> 
>> Best Regards
>>        Sebastian
>> 
>>> On Mar 15, 2019, at 11:46, Dave Taht <dave.taht@gmail.com> wrote:
>>> 
>>> Bufferbloat.net's ecn-sane working group members have a co-ordinated response to your efforts brewing but it's not ready yet. We have a worldwide team of linux and freebsd developers co-ordinating on landing code for our competing proposal "Some Congestion Experienced", which we submitted to tsvwg last sunday.
>>> 
>>> That draft is under continuous revision, here:
>>> 
>>> https://github.com/dtaht/bufferbloat-rfcs/blob/master/sce/draft-morton-taht-tsvwg-sce.txt
>>> 
>>> Our Linux and FreeBSD team is also flying into prague for SCE presentations at netdevconf and ietf.
>>> 
>>> Some background to this: after the L4S/TCP Prague/and dualpi experiments appeared stalled out indefinitely in the IETF, and with our own frustration with IETF processes, bufferbloat.net project members publicly formed our own working group to look into the problems with ecn, back in august of last year.
>>> 
>>> Its charter is here: https://www.bufferbloat.net/projects/ecn-sane/wiki/
>>> 
>>> We were unaware, until last month, that the cable industry had 16 months back gone and formed its own private working group also, and was intending to turn the tcp prague/l4s/dualpi IETF "experiments" into an actual DOCSIS standard.
>>> 
>>> Our SCE proposal appears to be backward compatible with the existing 10s-100s of millions of ecn-enabled fq_codel[1] and sch_cake[2] deployments, and doesn't require any changes to any RFC3168 tcps (or any tcp-friendly congestion control) at all in order to basically work. tcp-prague is subtly incompatible with that, and dualpi, more so. Our proposal is different also, it proposes some receiver side changes in order to get the full benefit of SCE while remaining backward compatible with the existing meaning of the CE codepoint.
>>> 
>>> In either case, either approach essentially permanently redefines the ECT_1 codepoint incompatibly, once and for all, and for all time. This is a final battle over the meaning of a single bit in IP, and I expect the debates to be as difficult as the ones described in https://www.ietf.org/rfc/ien/ien137.txt - I would really, really, really prefer that they stay technical and not veer into politics, but I have little hope for that.
>>> 
>>> The members of the ecn-sane working group are delighted to finally hear that running code for tcp-prague might land this ietf, and look forward to finally testing the whole l4s/tcpprague/dualpi architecture in conjunction with the flent.org 's and irtt's exhaustive suite of tests and servers in the cloud in the coming months, both against our existing, deployed, fq_codel, fq_pie, cake and pie derived solutions and our new SCE proposal. We hope to finally be able to write new tests for flent in particular, that can show tcpprague off in the ways that are important to those developing it. Flent has some basic dctcp tests, but nothing that can get down below a 20ms sample rate on modern hardware. (currently. It's easy to add tests, flent is written in python)
>>> 
>>> We also hope that more test tools and implementations in ns2 and ns3 show up for tcpprauge  and dualpi show up soon also, from members of those projects.
>>> 
>>> Note: sunday's dual-pi linux submission was kicked back from the linux networking developers due to some technical and legal problems with linux net-next HEAD ( https://patchwork.ozlabs.org/patch/1054521/  ) , and I do hope that a corrected version lands soon, so we can safely test it with current versions of OpenWrt, etc.
>>> 
>>> Finally, running code. Will we find consensus?
>>> 
>>> Thx!
>>> 
>>> 
>>> [1] https://tools.ietf.org/html/rfc8290
>>> [2] sch_cake was available for 3 years out of tree and was mainlined last august, in linux 4.19. It is partially described by "Piece of CAKE: A Comprehensive Queue Management Solution for Home Gateways" "https://arxiv.org/pdf/1804.07617.pdf
>>> 
>>> A second paper describing its fq_codel-derived "cobalt" AQM algorithm is awaiting publication in a peer reviewed journal. It has been part of openwrt and the related sqm-scripts for many years and is widely deployed on multiple commercial products, such as those from eero and evenroute.
>>> 
>>> Cake has a docsis specific mode which we longed for cablelabs to evaluate.
>>> 
>>> 
>>> On Fri, Mar 15, 2019 at 2:33 AM Bob Briscoe <ietf@bobbriscoe.net> wrote:
>>> Forwarding to tcpm & iccrg - apologies if you were already on one of the lists that received this.
>>> 
>>> Olivier has been working hard on integrating the pieces of a Linux implementation of TCP Prague, and is close to having a version ported against the tip of the Linux mainline tree. This is his request for more people to get involved.
>>> 
>>> 
>>> Bob
>>> 
>>> 
>>> -------- Forwarded Message --------
>>> Subject:      [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104
>>> Date: Wed, 6 Mar 2019 10:26:05 +0000
>>> From: Tilmans, Olivier (Nokia - BE/Antwerp) <olivier.tilmans@nokia-bell-labs.com>
>>> To:   hackathon@ietf.org <hackathon@ietf.org>, tcpprague@ietf.org <tcpprague@ietf.org>
>>> CC:   dlebrun@google.com <dlebrun@google.com>, Joakim Misund <joakim.misund@gmail.com>, Bob Briscoe <research@bobbriscoe.net>, Quentin De Coninck <quentin.deconinck@uclouvain.be>, François Michel <francois.michel@uclouvain.be>, Mirja Kuehlewind <mirja.kuehlewind@tik.ee.ethz.ch>, Maxime Piraux <maxime.piraux@uclouvain.be>, Olga Albisser <olga@albisser.org>, Fabien Duchêne <fabien.duchene@uclouvain.be>, De Schepper, Koen (Nokia - BE/Antwerp) <koen.de_schepper@nokia-bell-labs.com>
>>> 
>>> Hi all,
>>> 
>>> We'll be working on the "TCP Prague" congestion control/L4S architecture during the IETF-104 hackaton.
>>> This topics aims at accelerating the work that started during the IETF93 (coincidentally also in Prague), in order to get TCP Prague to an 'usable' state—i.e., meet the safety requirements and have supporting materials (e.g., VMs, labs) to let people experiment with it. Depending on people's interest, prototyping something similar for QUIC is another possible output.
>>> 
>>> Details and links to resources/supporting drafts are available at https://trac.ietf.org/trac/ietf/meeting/wiki/104hackathon#tcp-prague and copied below.
>>> Additionally, few topics will presented during netdev 0x13 the week before.
>>> 
>>> See you in Prague.
>>> 
>>> Best,
>>> Olivier
>>> 
>>> 
>>> Implementation and experimentation of TCP Prague/L4S
>>> 
>>> * Champion
>>> * Olivier Tilmans <olivier.tilmans at nokia-bell-labs.com>
>>> * Projects
>>> * Prototype the "TCP Prague" congestion control on Linux
>>> * Finalize the implementation of accurate ECN (draft conformance), and port it on Linux v5.x * Build tooling around L4S to let people experiment with the technology (e.g., virtual machine, or mininet labs)
>>> * Work towards "QUIC Prague"
>>> * Resources
>>> * TCP Prague
>>> * Repository — https://github.com/L4STeam/tcp-prague
>>> * Requirements — https://tools.ietf.org/html/draft-ietf-tsvwg-ecn-l4s-id-05#page-21
>>> * Upcoming netdev talk — https://netdevconf.org/0x13/session.html?talk-tcp-prague-l4s
>>> * Accurate ECN
>>> * Specs — https://tools.ietf.org/html/draft-ietf-tcpm-accurate-ecn-07
>>> * Implementation for Linux v4.17 — https://github.com/mirjak/linux-accecn
>>> * Past netdev talk — https://www.netdevconf.org/2.2/session.html?kuhlewind-accecn-talk
>>> * Paced Chirping * Repository — https://github.com/JoakimMisund/PacedChirping
>>> * Upcoming netdev talk — https://netdevconf.org/0x13/session.html?talk-chirp
>>> * L4S architecture
>>> * Specs — https://tools.ietf.org/html/draft-ietf-tsvwg-l4s-arch-03
>>> * DualPI2 AQM
>>> * Specs — https://tools.ietf.org/html/draft-ietf-tsvwg-aqm-dualq-coupled-08
>>> * Repository — https://github.com/L4STeam/sch_dualpi2_upstream
>>> * Upcoming netdev talk — https://netdevconf.org/0x13/session.html?talk-DUALPI2-AQM
>>> * RITE Project — https://riteproject.eu/dctth/#code
>>> _______________________________________________
>>> tcpPrague mailing list
>>> tcpPrague@ietf.org
>>> https://www.ietf.org/mailman/listinfo/tcpprague
>>> _______________________________________________
>>> iccrg mailing list
>>> iccrg@irtf.org
>>> https://www.irtf.org/mailman/listinfo/iccrg
>>> 
>>> 
>>> --
>>> 
>>> Dave Täht
>>> CTO, TekLibre, LLC
>>> http://www.teklibre.com
>>> Tel: 1-831-205-9740
>>> _______________________________________________
>>> Bloat mailing list
>>> Bloat@lists.bufferbloat.net
>>> https://lists.bufferbloat.net/listinfo/bloat
>> 
> 
> 
> --
> 
> Dave Täht
> CTO, TekLibre, LLC
> http://www.teklibre.com
> Tel: 1-831-205-9740

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[David P. Reed]

[-- Attachment #1: Type: text/plain, Size: 18339 bytes --]


The absolute fundamental issue with diffserv, IMO, is that the carriers cannot agree on an actual specification of what routers and gateways are supposed to do, while being compatible with the core principle of the IP layer: do not hold packets if they cause increasing queueing delay. (this is in the Best Practices RFC)
 
And it's not for lack of trying. Dave Clark led a working group at the MIT communications futures program (where I was a principle) that included most major backbone providers' key folks that was specifically focused on getting a widespread agreement on what any of the code points might mean, not as bullshit English descriptions of what kind of traffic each one represented, but as an operational description of what should be done by a router to manage its queues.
 
They couldn't even agree (after about 18 months of meetings) about what the bullshit English intent was, much less what operational semantics in the packet forwarding network had to be.
 
So if the responsible network engineers in the carriers cannot agree on anything, IETF is wasting its time.
 
 
 
 
-----Original Message-----
From: "Sebastian Moeller" <moeller0@gmx.de>
Sent: Friday, March 15, 2019 11:52am
To: "Dave Täht" <dave.taht@gmail.com>
Cc: ecn-sane@lists.bufferbloat.net, "bloat" <bloat@lists.bufferbloat.net>
Subject: Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104



Hi Dave,


> On Mar 15, 2019, at 15:06, Dave Taht <dave.taht@gmail.com> wrote:
> 
> I would really prefer to move this discussion to the ecn-sane mailing
> list, as IMHO, ecn is generally such a tiny thing needed for good
> congestion control compared to better transports like pacing + bbr,
> and things like bql, fq, and aqm using drop.
> 
> I'm going to keep cc-ing that list in the hope that we can keep better
> track of the discussion here.

 Ah, sure, I basically wanted to avoid annoying the ietf lists as I feel out of place there, having only had a cursory read of the relevant RFCs.


> 
> On Fri, Mar 15, 2019 at 6:01 AM Sebastian Moeller <moeller0@gmx.de> wrote:
>> 
>> Hi Dave,
>> 
>> I pruned the CC list as I am out of my league here and want to restrict the radius of my embarrassment to those that already know my level of incompetence before hand.
> 
> IMHO, your work on educating the OpenWrt community over the years on
> how to use sqm, makes you much more than "only a grasshopper". You
> have a firm grip on what can be achieved in the real world.
> 
>> 
>> That said, having read through the L4S architecture description and the related appendices of draft-ietf-tsvwg-ecn-l4s-id-05 I came to the conclusion, that this is a mess.
> 
> I am so glad someone other than I has now read it.
> 
>> The L4S project proposes a really wide-ranging change of basically the internet (but allow a concurrent operation with legacy probably to cater to the fact that an internet-wide flag-day seems daunting to organize). But then they chicken out when figuring out how to differentiate between their new and the old by proposing to use ECT(1) for a purpose outside of its nominal purpose namely explicit congestion notification, why not think bolder? If the plan is to change everything the feasibility can not hinge upon the ability to re-using one old legacy bit, can it...
>> Conceptually it seems much cleaner to use ECT(1) for congestion notification directly (there are already proposals out there and SCE just added another fully back-ward compatible one) and find another way to mark l4s traffic, sure that is going to be hard and inconvenient, but if you set out to change the internet that is par for the course.
>> IMHO they would do more good if they actually fought for a better use of the 6 DSCP bits instead. (say by splitting into two groups of 3 bits, one group for reduced diffserv and one group for new features, that would even
> 
> The existing diffserv deployment is a failure.

 Which is a shame, but one RFC's failure is another one's opportunity.


> I have another ID
> cooking that suggests a better way, going forward, to use them, but I
> do not feel at this time it would be useful to present. One big battle
> at a time.

:)

> That ID is very simple, it basically proposes that all
> diffserv codepoints be passed through ISPs and transit providers
> unchanged, and if any given codepoint must be changed, the only
> permissible change is to 0 (BE), and MUST be not be remarked to
> anything else, especially not CS1.

 I like the simplicity, but I also like the split into two groups of 3 bits, say "active bit pattern" (for transport purposes) and "intenden bit pattern" for the sender to transmit intent, which than can be conveyed lossless to the receiver; my gut feeling is that throwing the transport people a bone here might work better, as in the end they are the one that will carry the "burden" of the change. IMHO this has the additional advantage that it will make "tabula rasa" of the existing distict set of bit patterns used in the real world. Which in turn probably is this ideas downfall...


> 
>> allow for concurrent use of the inevitable L5S and L6S ;) ). Especially since as far as I can understand l4s actually would like to have a more gradual congestion information stream than classic ECN, and since they need to modify DCTCP anyway to make it save for the wider internet, replacing its ECN response should be well inside the scope of work they already have on their list.
> 
> Next up for sce was going to be to find if dctcp could be modified to
> use it. Also, bittorrent.

 YES! I endorse this message.

> 
>> If I sound a bit miffed, it is because after reading https://tools.ietf.org/html/draft-ietf-tsvwg-l4s-arch-03 I do not have the feeling they are trying to build abetter internet, but rather that they are building an internet where I can be a better "product" and customer of newfangled services, and I do not look forward to such a facebooky future with much enthusiasm.
> 
> I have rigorously tried to keep the network neutrality debate out of
> this.

 And I really do not want to start this here, as I agree that this is about a technical question. That said, I had hoped more out of the l4s promises from an end-user perspective. Then again, it if this is going to happen it needs the ISPs buy-in so it might be politically wise to emphasize the advantages for ISPs.


> dualpi is just another aqm that needs the same thorough
> technical and public evaluation done to it that pie, codel, fq_codel
> were subjected to.

+1, I note that the main argument against fq is "we can do it with two" without a convincing argument why two is better than the few 100s you realistically will never need for fq even on an busy core router.

> The use of ect_1 in dualpi for it is nuts IMHO,

 At least it is unclean...

> and
> I'd vastly prefer that another L4S codepoint be added to make it work,
> but any attempt to do so would also require industry consolidation on
> that ID and that would be distracting at this time.

 But as I said, L4S aims to change everything so why stop there ;)

> 
> It appears, also, ironically, (I have confirmation from several
> sources now) that cake, fq_codel and dualpi are now illegal for an ISP
> to use in their provided equipment under california law.

 I will happily look at specific sections of code if pointed to, but I will not actively search for. At least the European net neutrality rules do not make any of these illegal, as the rules allow for traffic management (and special services at extra cost as long as these are not built be restricting the best-effort net, no idea how that should be poiced) (and in the end the rules only apply for ISPs in one's own network one can DPI to a far greater extent if one is such inclined).


> The idea of
> one day having to appear in court to defend our key algorithms reminds
> me of the famous john fogerty case where he demonstrated how blues
> music was made.

 I see a nice art-house movie coming up.


> 
> I wish I knew a lawyer willing to take on "bufferbloat.net vs the
> state of california", though, as it may come down to that.
> 
> I blew up on this part of the issue here:
> http://blog.cerowrt.org/post/net_neutrality_customers/

 I read that, but it does not reflect to well on the situation this side of the pond. We had situations where ISPs worked hard (but without success) to switch from their flat-rate access to introduce volume caps, that served a dual purpose, a) extracting more revenue from customers and b) allowing to make "zero-rating" deals with content-providers (which in the end are also payed for by the end-users, indirectly). Sure, this is all normal in business, but that does not necessarily mean that I do need to like being a pawn in a business transaction between global corporations. (I consider this to be at least somewhat related to the net neutrality debate).

Best Regards
 Sebastian


>> 
>> I hope that the discussion in Prague go well and a compromise/consense can be hashed out as I see different implementations duking it out here, but the overall goal of the competitors seems quite compatible, improving the internet by focussing on latency.
>> 
>> Best Regards
>> Sebastian
>> 
>>> On Mar 15, 2019, at 11:46, Dave Taht <dave.taht@gmail.com> wrote:
>>> 
>>> Bufferbloat.net's ecn-sane working group members have a co-ordinated response to your efforts brewing but it's not ready yet. We have a worldwide team of linux and freebsd developers co-ordinating on landing code for our competing proposal "Some Congestion Experienced", which we submitted to tsvwg last sunday.
>>> 
>>> That draft is under continuous revision, here:
>>> 
>>> https://github.com/dtaht/bufferbloat-rfcs/blob/master/sce/draft-morton-taht-tsvwg-sce.txt
>>> 
>>> Our Linux and FreeBSD team is also flying into prague for SCE presentations at netdevconf and ietf.
>>> 
>>> Some background to this: after the L4S/TCP Prague/and dualpi experiments appeared stalled out indefinitely in the IETF, and with our own frustration with IETF processes, bufferbloat.net project members publicly formed our own working group to look into the problems with ecn, back in august of last year.
>>> 
>>> Its charter is here: https://www.bufferbloat.net/projects/ecn-sane/wiki/
>>> 
>>> We were unaware, until last month, that the cable industry had 16 months back gone and formed its own private working group also, and was intending to turn the tcp prague/l4s/dualpi IETF "experiments" into an actual DOCSIS standard.
>>> 
>>> Our SCE proposal appears to be backward compatible with the existing 10s-100s of millions of ecn-enabled fq_codel[1] and sch_cake[2] deployments, and doesn't require any changes to any RFC3168 tcps (or any tcp-friendly congestion control) at all in order to basically work. tcp-prague is subtly incompatible with that, and dualpi, more so. Our proposal is different also, it proposes some receiver side changes in order to get the full benefit of SCE while remaining backward compatible with the existing meaning of the CE codepoint.
>>> 
>>> In either case, either approach essentially permanently redefines the ECT_1 codepoint incompatibly, once and for all, and for all time. This is a final battle over the meaning of a single bit in IP, and I expect the debates to be as difficult as the ones described in https://www.ietf.org/rfc/ien/ien137.txt - I would really, really, really prefer that they stay technical and not veer into politics, but I have little hope for that.
>>> 
>>> The members of the ecn-sane working group are delighted to finally hear that running code for tcp-prague might land this ietf, and look forward to finally testing the whole l4s/tcpprague/dualpi architecture in conjunction with the flent.org 's and irtt's exhaustive suite of tests and servers in the cloud in the coming months, both against our existing, deployed, fq_codel, fq_pie, cake and pie derived solutions and our new SCE proposal. We hope to finally be able to write new tests for flent in particular, that can show tcpprague off in the ways that are important to those developing it. Flent has some basic dctcp tests, but nothing that can get down below a 20ms sample rate on modern hardware. (currently. It's easy to add tests, flent is written in python)
>>> 
>>> We also hope that more test tools and implementations in ns2 and ns3 show up for tcpprauge and dualpi show up soon also, from members of those projects.
>>> 
>>> Note: sunday's dual-pi linux submission was kicked back from the linux networking developers due to some technical and legal problems with linux net-next HEAD ( https://patchwork.ozlabs.org/patch/1054521/ ) , and I do hope that a corrected version lands soon, so we can safely test it with current versions of OpenWrt, etc.
>>> 
>>> Finally, running code. Will we find consensus?
>>> 
>>> Thx!
>>> 
>>> 
>>> [1] https://tools.ietf.org/html/rfc8290
>>> [2] sch_cake was available for 3 years out of tree and was mainlined last august, in linux 4.19. It is partially described by "Piece of CAKE: A Comprehensive Queue Management Solution for Home Gateways" "https://arxiv.org/pdf/1804.07617.pdf
>>> 
>>> A second paper describing its fq_codel-derived "cobalt" AQM algorithm is awaiting publication in a peer reviewed journal. It has been part of openwrt and the related sqm-scripts for many years and is widely deployed on multiple commercial products, such as those from eero and evenroute.
>>> 
>>> Cake has a docsis specific mode which we longed for cablelabs to evaluate.
>>> 
>>> 
>>> On Fri, Mar 15, 2019 at 2:33 AM Bob Briscoe <ietf@bobbriscoe.net> wrote:
>>> Forwarding to tcpm & iccrg - apologies if you were already on one of the lists that received this.
>>> 
>>> Olivier has been working hard on integrating the pieces of a Linux implementation of TCP Prague, and is close to having a version ported against the tip of the Linux mainline tree. This is his request for more people to get involved.
>>> 
>>> 
>>> Bob
>>> 
>>> 
>>> -------- Forwarded Message --------
>>> Subject: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104
>>> Date: Wed, 6 Mar 2019 10:26:05 +0000
>>> From: Tilmans, Olivier (Nokia - BE/Antwerp) <olivier.tilmans@nokia-bell-labs.com>
>>> To: hackathon@ietf.org <hackathon@ietf.org>, tcpprague@ietf.org <tcpprague@ietf.org>
>>> CC: dlebrun@google.com <dlebrun@google.com>, Joakim Misund <joakim.misund@gmail.com>, Bob Briscoe <research@bobbriscoe.net>, Quentin De Coninck <quentin.deconinck@uclouvain.be>, François Michel <francois.michel@uclouvain.be>, Mirja Kuehlewind <mirja.kuehlewind@tik.ee.ethz.ch>, Maxime Piraux <maxime.piraux@uclouvain.be>, Olga Albisser <olga@albisser.org>, Fabien Duchêne <fabien.duchene@uclouvain.be>, De Schepper, Koen (Nokia - BE/Antwerp) <koen.de_schepper@nokia-bell-labs.com>
>>> 
>>> Hi all,
>>> 
>>> We'll be working on the "TCP Prague" congestion control/L4S architecture during the IETF-104 hackaton.
>>> This topics aims at accelerating the work that started during the IETF93 (coincidentally also in Prague), in order to get TCP Prague to an 'usable' state—i.e., meet the safety requirements and have supporting materials (e.g., VMs, labs) to let people experiment with it. Depending on people's interest, prototyping something similar for QUIC is another possible output.
>>> 
>>> Details and links to resources/supporting drafts are available at https://trac.ietf.org/trac/ietf/meeting/wiki/104hackathon#tcp-prague and copied below.
>>> Additionally, few topics will presented during netdev 0x13 the week before.
>>> 
>>> See you in Prague.
>>> 
>>> Best,
>>> Olivier
>>> 
>>> 
>>> Implementation and experimentation of TCP Prague/L4S
>>> 
>>> * Champion
>>> * Olivier Tilmans <olivier.tilmans at nokia-bell-labs.com>
>>> * Projects
>>> * Prototype the "TCP Prague" congestion control on Linux
>>> * Finalize the implementation of accurate ECN (draft conformance), and port it on Linux v5.x * Build tooling around L4S to let people experiment with the technology (e.g., virtual machine, or mininet labs)
>>> * Work towards "QUIC Prague"
>>> * Resources
>>> * TCP Prague
>>> * Repository — https://github.com/L4STeam/tcp-prague
>>> * Requirements — https://tools.ietf.org/html/draft-ietf-tsvwg-ecn-l4s-id-05#page-21
>>> * Upcoming netdev talk — https://netdevconf.org/0x13/session.html?talk-tcp-prague-l4s
>>> * Accurate ECN
>>> * Specs — https://tools.ietf.org/html/draft-ietf-tcpm-accurate-ecn-07
>>> * Implementation for Linux v4.17 — https://github.com/mirjak/linux-accecn
>>> * Past netdev talk — https://www.netdevconf.org/2.2/session.html?kuhlewind-accecn-talk
>>> * Paced Chirping * Repository — https://github.com/JoakimMisund/PacedChirping
>>> * Upcoming netdev talk — https://netdevconf.org/0x13/session.html?talk-chirp
>>> * L4S architecture
>>> * Specs — https://tools.ietf.org/html/draft-ietf-tsvwg-l4s-arch-03
>>> * DualPI2 AQM
>>> * Specs — https://tools.ietf.org/html/draft-ietf-tsvwg-aqm-dualq-coupled-08
>>> * Repository — https://github.com/L4STeam/sch_dualpi2_upstream
>>> * Upcoming netdev talk — https://netdevconf.org/0x13/session.html?talk-DUALPI2-AQM
>>> * RITE Project — https://riteproject.eu/dctth/#code
>>> _______________________________________________
>>> tcpPrague mailing list
>>> tcpPrague@ietf.org
>>> https://www.ietf.org/mailman/listinfo/tcpprague
>>> _______________________________________________
>>> iccrg mailing list
>>> iccrg@irtf.org
>>> https://www.irtf.org/mailman/listinfo/iccrg
>>> 
>>> 
>>> --
>>> 
>>> Dave Täht
>>> CTO, TekLibre, LLC
>>> http://www.teklibre.com
>>> Tel: 1-831-205-9740
>>> _______________________________________________
>>> Bloat mailing list
>>> Bloat@lists.bufferbloat.net
>>> https://lists.bufferbloat.net/listinfo/bloat
>> 
> 
> 
> --
> 
> Dave Täht
> CTO, TekLibre, LLC
> http://www.teklibre.com
> Tel: 1-831-205-9740

_______________________________________________
Ecn-sane mailing list
Ecn-sane@lists.bufferbloat.net
https://lists.bufferbloat.net/listinfo/ecn-sane

[-- Attachment #2: Type: text/html, Size: 22241 bytes --]

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Sebastian Moeller]

On March 15, 2019 6:01:23 PM GMT+01:00, "David P. Reed" <dpreed@deepplum.com> wrote:
>
>The absolute fundamental issue with diffserv, IMO, is that the carriers
>cannot agree on an actual specification of what routers and gateways
>are supposed to do, while being compatible with the core principle of
>the IP layer: do not hold packets if they cause increasing queueing
>delay. (this is in the Best Practices RFC)
> 

IMHO it is the Charme of the 2 times 3 bits approach, that carriers get 3 bits they can do with whatever they want. As VLAN tags and MPLS? only support 3 bit priorities this looks to me like a match made in heaven, and we get 3 bits with end to end guarantees. Not that rolling that out would ever work in reality....

Best Regards

Sebastian

And yes, this is not an idea I came up with, I just forgot who proposed that initially.


>And it's not for lack of trying. Dave Clark led a working group at the
>MIT communications futures program (where I was a principle) that
>included most major backbone providers' key folks that was specifically
>focused on getting a widespread agreement on what any of the code
>points might mean, not as bullshit English descriptions of what kind of
>traffic each one represented, but as an operational description of what
>should be done by a router to manage its queues.
> 
>They couldn't even agree (after about 18 months of meetings) about what
>the bullshit English intent was, much less what operational semantics
>in the packet forwarding network had to be.
> 
>So if the responsible network engineers in the carriers cannot agree on
>anything, IETF is wasting its time.
> 
> 
> 
> 
>-----Original Message-----
>From: "Sebastian Moeller" <moeller0@gmx.de>
>Sent: Friday, March 15, 2019 11:52am
>To: "Dave Täht" <dave.taht@gmail.com>
>Cc: ecn-sane@lists.bufferbloat.net, "bloat"
><bloat@lists.bufferbloat.net>
>Subject: Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation
>and experimentation of TCP Prague/L4S hackaton at IETF104
>
>
>
>Hi Dave,
>
>
>> On Mar 15, 2019, at 15:06, Dave Taht <dave.taht@gmail.com> wrote:
>> 
>> I would really prefer to move this discussion to the ecn-sane mailing
>> list, as IMHO, ecn is generally such a tiny thing needed for good
>> congestion control compared to better transports like pacing + bbr,
>> and things like bql, fq, and aqm using drop.
>> 
>> I'm going to keep cc-ing that list in the hope that we can keep
>better
>> track of the discussion here.
>
>Ah, sure, I basically wanted to avoid annoying the ietf lists as I feel
>out of place there, having only had a cursory read of the relevant
>RFCs.
>
>
>> 
>> On Fri, Mar 15, 2019 at 6:01 AM Sebastian Moeller <moeller0@gmx.de>
>wrote:
>>> 
>>> Hi Dave,
>>> 
>>> I pruned the CC list as I am out of my league here and want to
>restrict the radius of my embarrassment to those that already know my
>level of incompetence before hand.
>> 
>> IMHO, your work on educating the OpenWrt community over the years on
>> how to use sqm, makes you much more than "only a grasshopper". You
>> have a firm grip on what can be achieved in the real world.
>> 
>>> 
>>> That said, having read through the L4S architecture description and
>the related appendices of draft-ietf-tsvwg-ecn-l4s-id-05 I came to the
>conclusion, that this is a mess.
>> 
>> I am so glad someone other than I has now read it.
>> 
>>> The L4S project proposes a really wide-ranging change of basically
>the internet (but allow a concurrent operation with legacy probably to
>cater to the fact that an internet-wide flag-day seems daunting to
>organize). But then they chicken out when figuring out how to
>differentiate between their new and the old by proposing to use ECT(1)
>for a purpose outside of its nominal purpose namely explicit congestion
>notification, why not think bolder? If the plan is to change everything
>the feasibility can not hinge upon the ability to re-using one old
>legacy bit, can it...
>>> Conceptually it seems much cleaner to use ECT(1) for congestion
>notification directly (there are already proposals out there and SCE
>just added another fully back-ward compatible one) and find another way
>to mark l4s traffic, sure that is going to be hard and inconvenient,
>but if you set out to change the internet that is par for the course.
>>> IMHO they would do more good if they actually fought for a better
>use of the 6 DSCP bits instead. (say by splitting into two groups of 3
>bits, one group for reduced diffserv and one group for new features,
>that would even
>> 
>> The existing diffserv deployment is a failure.
>
> Which is a shame, but one RFC's failure is another one's opportunity.
>
>
>> I have another ID
>> cooking that suggests a better way, going forward, to use them, but I
>> do not feel at this time it would be useful to present. One big
>battle
>> at a time.
>
>:)
>
>> That ID is very simple, it basically proposes that all
>> diffserv codepoints be passed through ISPs and transit providers
>> unchanged, and if any given codepoint must be changed, the only
>> permissible change is to 0 (BE), and MUST be not be remarked to
>> anything else, especially not CS1.
>
>I like the simplicity, but I also like the split into two groups of 3
>bits, say "active bit pattern" (for transport purposes) and "intenden
>bit pattern" for the sender to transmit intent, which than can be
>conveyed lossless to the receiver; my gut feeling is that throwing the
>transport people a bone here might work better, as in the end they are
>the one that will carry the "burden" of the change. IMHO this has the
>additional advantage that it will make "tabula rasa" of the existing
>distict set of bit patterns used in the real world. Which in turn
>probably is this ideas downfall...
>
>
>> 
>>> allow for concurrent use of the inevitable L5S and L6S ;) ).
>Especially since as far as I can understand l4s actually would like to
>have a more gradual congestion information stream than classic ECN, and
>since they need to modify DCTCP anyway to make it save for the wider
>internet, replacing its ECN response should be well inside the scope of
>work they already have on their list.
>> 
>> Next up for sce was going to be to find if dctcp could be modified to
>> use it. Also, bittorrent.
>
> YES! I endorse this message.
>
>> 
>>> If I sound a bit miffed, it is because after reading
>https://tools.ietf.org/html/draft-ietf-tsvwg-l4s-arch-03 I do not have
>the feeling they are trying to build abetter internet, but rather that
>they are building an internet where I can be a better "product" and
>customer of newfangled services, and I do not look forward to such a
>facebooky future with much enthusiasm.
>> 
>> I have rigorously tried to keep the network neutrality debate out of
>> this.
>
>And I really do not want to start this here, as I agree that this is
>about a technical question. That said, I had hoped more out of the l4s
>promises from an end-user perspective. Then again, it if this is going
>to happen it needs the ISPs buy-in so it might be politically wise to
>emphasize the advantages for ISPs.
>
>
>> dualpi is just another aqm that needs the same thorough
>> technical and public evaluation done to it that pie, codel, fq_codel
>> were subjected to.
>
>+1, I note that the main argument against fq is "we can do it with two"
>without a convincing argument why two is better than the few 100s you
>realistically will never need for fq even on an busy core router.
>
>> The use of ect_1 in dualpi for it is nuts IMHO,
>
> At least it is unclean...
>
>> and
>> I'd vastly prefer that another L4S codepoint be added to make it
>work,
>> but any attempt to do so would also require industry consolidation on
>> that ID and that would be distracting at this time.
>
> But as I said, L4S aims to change everything so why stop there ;)
>
>> 
>> It appears, also, ironically, (I have confirmation from several
>> sources now) that cake, fq_codel and dualpi are now illegal for an
>ISP
>> to use in their provided equipment under california law.
>
>I will happily look at specific sections of code if pointed to, but I
>will not actively search for. At least the European net neutrality
>rules do not make any of these illegal, as the rules allow for traffic
>management (and special services at extra cost as long as these are not
>built be restricting the best-effort net, no idea how that should be
>poiced) (and in the end the rules only apply for ISPs in one's own
>network one can DPI to a far greater extent if one is such inclined).
>
>
>> The idea of
>> one day having to appear in court to defend our key algorithms
>reminds
>> me of the famous john fogerty case where he demonstrated how blues
>> music was made.
>
> I see a nice art-house movie coming up.
>
>
>> 
>> I wish I knew a lawyer willing to take on "bufferbloat.net vs the
>> state of california", though, as it may come down to that.
>> 
>> I blew up on this part of the issue here:
>> http://blog.cerowrt.org/post/net_neutrality_customers/
>
>I read that, but it does not reflect to well on the situation this side
>of the pond. We had situations where ISPs worked hard (but without
>success) to switch from their flat-rate access to introduce volume
>caps, that served a dual purpose, a) extracting more revenue from
>customers and b) allowing to make "zero-rating" deals with
>content-providers (which in the end are also payed for by the
>end-users, indirectly). Sure, this is all normal in business, but that
>does not necessarily mean that I do need to like being a pawn in a
>business transaction between global corporations. (I consider this to
>be at least somewhat related to the net neutrality debate).
>
>Best Regards
> Sebastian
>
>
>>> 
>>> I hope that the discussion in Prague go well and a
>compromise/consense can be hashed out as I see different
>implementations duking it out here, but the overall goal of the
>competitors seems quite compatible, improving the internet by focussing
>on latency.
>>> 
>>> Best Regards
>>> Sebastian
>>> 
>>>> On Mar 15, 2019, at 11:46, Dave Taht <dave.taht@gmail.com> wrote:
>>>> 
>>>> Bufferbloat.net's ecn-sane working group members have a
>co-ordinated response to your efforts brewing but it's not ready yet.
>We have a worldwide team of linux and freebsd developers co-ordinating
>on landing code for our competing proposal "Some Congestion
>Experienced", which we submitted to tsvwg last sunday.
>>>> 
>>>> That draft is under continuous revision, here:
>>>> 
>>>>
>https://github.com/dtaht/bufferbloat-rfcs/blob/master/sce/draft-morton-taht-tsvwg-sce.txt
>>>> 
>>>> Our Linux and FreeBSD team is also flying into prague for SCE
>presentations at netdevconf and ietf.
>>>> 
>>>> Some background to this: after the L4S/TCP Prague/and dualpi
>experiments appeared stalled out indefinitely in the IETF, and with our
>own frustration with IETF processes, bufferbloat.net project members
>publicly formed our own working group to look into the problems with
>ecn, back in august of last year.
>>>> 
>>>> Its charter is here:
>https://www.bufferbloat.net/projects/ecn-sane/wiki/
>>>> 
>>>> We were unaware, until last month, that the cable industry had 16
>months back gone and formed its own private working group also, and was
>intending to turn the tcp prague/l4s/dualpi IETF "experiments" into an
>actual DOCSIS standard.
>>>> 
>>>> Our SCE proposal appears to be backward compatible with the
>existing 10s-100s of millions of ecn-enabled fq_codel[1] and
>sch_cake[2] deployments, and doesn't require any changes to any RFC3168
>tcps (or any tcp-friendly congestion control) at all in order to
>basically work. tcp-prague is subtly incompatible with that, and
>dualpi, more so. Our proposal is different also, it proposes some
>receiver side changes in order to get the full benefit of SCE while
>remaining backward compatible with the existing meaning of the CE
>codepoint.
>>>> 
>>>> In either case, either approach essentially permanently redefines
>the ECT_1 codepoint incompatibly, once and for all, and for all time.
>This is a final battle over the meaning of a single bit in IP, and I
>expect the debates to be as difficult as the ones described in
>https://www.ietf.org/rfc/ien/ien137.txt - I would really, really,
>really prefer that they stay technical and not veer into politics, but
>I have little hope for that.
>>>> 
>>>> The members of the ecn-sane working group are delighted to finally
>hear that running code for tcp-prague might land this ietf, and look
>forward to finally testing the whole l4s/tcpprague/dualpi architecture
>in conjunction with the flent.org 's and irtt's exhaustive suite of
>tests and servers in the cloud in the coming months, both against our
>existing, deployed, fq_codel, fq_pie, cake and pie derived solutions
>and our new SCE proposal. We hope to finally be able to write new tests
>for flent in particular, that can show tcpprague off in the ways that
>are important to those developing it. Flent has some basic dctcp tests,
>but nothing that can get down below a 20ms sample rate on modern
>hardware. (currently. It's easy to add tests, flent is written in
>python)
>>>> 
>>>> We also hope that more test tools and implementations in ns2 and
>ns3 show up for tcpprauge and dualpi show up soon also, from members of
>those projects.
>>>> 
>>>> Note: sunday's dual-pi linux submission was kicked back from the
>linux networking developers due to some technical and legal problems
>with linux net-next HEAD ( https://patchwork.ozlabs.org/patch/1054521/
>) , and I do hope that a corrected version lands soon, so we can safely
>test it with current versions of OpenWrt, etc.
>>>> 
>>>> Finally, running code. Will we find consensus?
>>>> 
>>>> Thx!
>>>> 
>>>> 
>>>> [1] https://tools.ietf.org/html/rfc8290
>>>> [2] sch_cake was available for 3 years out of tree and was
>mainlined last august, in linux 4.19. It is partially described by
>"Piece of CAKE: A Comprehensive Queue Management Solution for Home
>Gateways" "https://arxiv.org/pdf/1804.07617.pdf
>>>> 
>>>> A second paper describing its fq_codel-derived "cobalt" AQM
>algorithm is awaiting publication in a peer reviewed journal. It has
>been part of openwrt and the related sqm-scripts for many years and is
>widely deployed on multiple commercial products, such as those from
>eero and evenroute.
>>>> 
>>>> Cake has a docsis specific mode which we longed for cablelabs to
>evaluate.
>>>> 
>>>> 
>>>> On Fri, Mar 15, 2019 at 2:33 AM Bob Briscoe <ietf@bobbriscoe.net>
>wrote:
>>>> Forwarding to tcpm & iccrg - apologies if you were already on one
>of the lists that received this.
>>>> 
>>>> Olivier has been working hard on integrating the pieces of a Linux
>implementation of TCP Prague, and is close to having a version ported
>against the tip of the Linux mainline tree. This is his request for
>more people to get involved.
>>>> 
>>>> 
>>>> Bob
>>>> 
>>>> 
>>>> -------- Forwarded Message --------
>>>> Subject: [tcpPrague] Implementation and experimentation of TCP
>Prague/L4S hackaton at IETF104
>>>> Date: Wed, 6 Mar 2019 10:26:05 +0000
>>>> From: Tilmans, Olivier (Nokia - BE/Antwerp)
><olivier.tilmans@nokia-bell-labs.com>
>>>> To: hackathon@ietf.org <hackathon@ietf.org>, tcpprague@ietf.org
><tcpprague@ietf.org>
>>>> CC: dlebrun@google.com <dlebrun@google.com>, Joakim Misund
><joakim.misund@gmail.com>, Bob Briscoe <research@bobbriscoe.net>,
>Quentin De Coninck <quentin.deconinck@uclouvain.be>, François Michel
><francois.michel@uclouvain.be>, Mirja Kuehlewind
><mirja.kuehlewind@tik.ee.ethz.ch>, Maxime Piraux
><maxime.piraux@uclouvain.be>, Olga Albisser <olga@albisser.org>, Fabien
>Duchêne <fabien.duchene@uclouvain.be>, De Schepper, Koen (Nokia -
>BE/Antwerp) <koen.de_schepper@nokia-bell-labs.com>
>>>> 
>>>> Hi all,
>>>> 
>>>> We'll be working on the "TCP Prague" congestion control/L4S
>architecture during the IETF-104 hackaton.
>>>> This topics aims at accelerating the work that started during the
>IETF93 (coincidentally also in Prague), in order to get TCP Prague to
>an 'usable' state—i.e., meet the safety requirements and have
>supporting materials (e.g., VMs, labs) to let people experiment with
>it. Depending on people's interest, prototyping something similar for
>QUIC is another possible output.
>>>> 
>>>> Details and links to resources/supporting drafts are available at
>https://trac.ietf.org/trac/ietf/meeting/wiki/104hackathon#tcp-prague
>and copied below.
>>>> Additionally, few topics will presented during netdev 0x13 the week
>before.
>>>> 
>>>> See you in Prague.
>>>> 
>>>> Best,
>>>> Olivier
>>>> 
>>>> 
>>>> Implementation and experimentation of TCP Prague/L4S
>>>> 
>>>> * Champion
>>>> * Olivier Tilmans <olivier.tilmans at nokia-bell-labs.com>
>>>> * Projects
>>>> * Prototype the "TCP Prague" congestion control on Linux
>>>> * Finalize the implementation of accurate ECN (draft conformance),
>and port it on Linux v5.x * Build tooling around L4S to let people
>experiment with the technology (e.g., virtual machine, or mininet labs)
>>>> * Work towards "QUIC Prague"
>>>> * Resources
>>>> * TCP Prague
>>>> * Repository — https://github.com/L4STeam/tcp-prague
>>>> * Requirements —
>https://tools.ietf.org/html/draft-ietf-tsvwg-ecn-l4s-id-05#page-21
>>>> * Upcoming netdev talk —
>https://netdevconf.org/0x13/session.html?talk-tcp-prague-l4s
>>>> * Accurate ECN
>>>> * Specs —
>https://tools.ietf.org/html/draft-ietf-tcpm-accurate-ecn-07
>>>> * Implementation for Linux v4.17 —
>https://github.com/mirjak/linux-accecn
>>>> * Past netdev talk —
>https://www.netdevconf.org/2.2/session.html?kuhlewind-accecn-talk
>>>> * Paced Chirping * Repository —
>https://github.com/JoakimMisund/PacedChirping
>>>> * Upcoming netdev talk —
>https://netdevconf.org/0x13/session.html?talk-chirp
>>>> * L4S architecture
>>>> * Specs — https://tools.ietf.org/html/draft-ietf-tsvwg-l4s-arch-03
>>>> * DualPI2 AQM
>>>> * Specs —
>https://tools.ietf.org/html/draft-ietf-tsvwg-aqm-dualq-coupled-08
>>>> * Repository — https://github.com/L4STeam/sch_dualpi2_upstream
>>>> * Upcoming netdev talk —
>https://netdevconf.org/0x13/session.html?talk-DUALPI2-AQM
>>>> * RITE Project — https://riteproject.eu/dctth/#code
>>>> _______________________________________________
>>>> tcpPrague mailing list
>>>> tcpPrague@ietf.org
>>>> https://www.ietf.org/mailman/listinfo/tcpprague
>>>> _______________________________________________
>>>> iccrg mailing list
>>>> iccrg@irtf.org
>>>> https://www.irtf.org/mailman/listinfo/iccrg
>>>> 
>>>> 
>>>> --
>>>> 
>>>> Dave Täht
>>>> CTO, TekLibre, LLC
>>>> http://www.teklibre.com
>>>> Tel: 1-831-205-9740
>>>> _______________________________________________
>>>> Bloat mailing list
>>>> Bloat@lists.bufferbloat.net
>>>> https://lists.bufferbloat.net/listinfo/bloat
>>> 
>> 
>> 
>> --
>> 
>> Dave Täht
>> CTO, TekLibre, LLC
>> http://www.teklibre.com
>> Tel: 1-831-205-9740
>
>_______________________________________________
>Ecn-sane mailing list
>Ecn-sane@lists.bufferbloat.net
>https://lists.bufferbloat.net/listinfo/ecn-sane

-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Mikael Abrahamsson]

On Fri, 15 Mar 2019, David P. Reed wrote:

> So if the responsible network engineers in the carriers cannot agree on 
> anything, IETF is wasting its time.

The IETF has already said that anything diffserv is domain-internal only. 
I have joined the effort of the LE PHB and see if we can get some kind of 
agreement and transparancy for a PHB that is aimed at customer access only 
and "drop most of me and my pals at any sign of customer access line 
congestion", and see if that can be agreed on.

Having a "lower-than-best-effort" diffserve codepoint might work, because 
it means worse treatment, not preferential treatment.

The problem with having DSCP CPs that indicate preferential treatment is 
typically a ddos magnet. See my emails on this topic on (this? other?) 
mailing lists where I try to create a three class buffering system saying 
"LE gets 5%, BE and 'everything-else' gets to split the difference".

I even got pushback on this here, and then we're not even close to people 
running large ISP networks who see ddos attacks happen hourly.

Saying L4S should "just use diffserv" is as constructive to say "go away 
and pound a rock" or "we want that bit pattern so.. screw you".

L4S has a much better possibility of actually getting deployment into the 
wider Internet packet-moving equipment than anything being talked about 
here. Same with PIE as opposed to FQ_CODEL. I know it's might not be as 
good, but it fits better into actual silicon and it's being proposed by 
people who actually have better channels into the people setting hard 
requirements.

I suggest you consider joining them instead of opposing them.

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Sebastian Moeller]

Hi Mikael,


> On Mar 15, 2019, at 19:36, Mikael Abrahamsson <swmike@swm.pp.se> wrote:
> 
> On Fri, 15 Mar 2019, David P. Reed wrote:
> 
>> So if the responsible network engineers in the carriers cannot agree on anything, IETF is wasting its time.
> 
> The IETF has already said that anything diffserv is domain-internal only. I have joined the effort of the LE PHB and see if we can get some kind of agreement and transparancy for a PHB that is aimed at customer access only and "drop most of me and my pals at any sign of customer access line congestion", and see if that can be agreed on.

	+1

> 
> Having a "lower-than-best-effort" diffserve codepoint might work, because it means worse treatment, not preferential treatment.
> 
> The problem with having DSCP CPs that indicate preferential treatment is typically a ddos magnet.

	Hence splitting it up, three for the current transport domain to do with as it sees fit and 3 for signaling intent; this very much does not give a guarantee that any intermediate hop will follow the intent, but only make it possible for the endpoints to transmit intent. This IMHO is completely compatible with a LE PHB and transports honoring that request. 

> See my emails on this topic on (this? other?) mailing lists where I try to create a three class buffering system saying "LE gets 5%, BE and 'everything-else' gets to split the difference".

	We can haggle over the numbers but that seems a) sane and b) underspecified...

> 
> I even got pushback on this here, and then we're not even close to people running large ISP networks who see ddos attacks happen hourly.
> 
> Saying L4S should "just use diffserv" is as constructive to say "go away and pound a rock" or "we want that bit pattern so.. screw you".

	But just nodding expertly when they go and claim an unrelated bit in the IP header for their separation l4s vs legacy (as if l4s would be the end all of network design), and then having resorting to modifying so-far not-deployed-at the edge DCTCP (instead of modifying well-deployed TCP) because they already spent the one bit usable to extend ECN for less binary congestion signaling in a backward-compatible fashion... I might be wording things to strongly here, but that is the general gist.

> 
> L4S has a much better possibility of actually getting deployment into the wider Internet packet-moving equipment than anything being talked about here.

	That is not a high bar to clear though...

> Same with PIE as opposed to FQ_CODEL. I know it's might not be as good,

	Debatable, and from my perspective this is the reason to talk about it at all.

> but it fits better into actual silicon

	Does it?

> and it's being proposed by people who actually have better channels into the people setting hard requirements.

	That would be great if the proposal would throw end-user like me a bone instead of treating me as the product. It would also help if the architectural RFC would not be so breathlessly over-hyping/over-promising... But they really need end-points to switch over to a neutered DCTCP before things start to make sense, so they actually need to convince end-users and so far they are doing a terrible job IMHO. But what do I know...

> 
> I suggest you consider joining them instead of opposing them.

	Join where? it pretty much looks like a "fait accompli" as they do seem way past the design stages and seem pretty much crystallized in what they see the path forward. 

Best Regards
	Sebastian

> 
> -- 
> Mikael Abrahamsson    email: swmike@swm.pp.se

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Jonathan Morton]

> On 15 Mar, 2019, at 8:36 pm, Mikael Abrahamsson <swmike@swm.pp.se> wrote:
> 
> Having a "lower-than-best-effort" diffserve codepoint might work, because it means worse treatment, not preferential treatment.
> 
> The problem with having DSCP CPs that indicate preferential treatment is typically a ddos magnet.

This is true, and also why I feel that just 2 bits should be sufficient for Diffserv (rather than 6).  They are sufficient to express four different optimisation targets:

0: Maximum Throughput (aka Best Effort)
1: Minimum Cost (aka Least Effort)
2: Minimum Latency (aka Maximum Responsiveness)
3: Minimum Loss (aka Maximum Reliability)

It is legitimate for traffic to request any of these four optimisations, with the explicit tradeoff of *not* necessarily getting optimisation in the other three dimensions.

The old TOS spec erred in specifying 4 non-exclusive bits to express this, in addition to 3 bits for a telegram-office style "priority level" (which was very much ripe for abuse if not strictly admission-controlled).  TOS was rightly considered a mess, but was replaced with Diffserv which was far too loose a spec to be useful in practice.

But that's a separate topic from ECN per se.

 - Jonathan Morton

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[David P. Reed]

[-- Attachment #1: Type: text/plain, Size: 2436 bytes --]


Just to throw in one more thing not well understood by engineers.
 
Economists I have discussed this with (real ones, not fringe right-wing true believers that the market "just works"), have observed that pricing (even dynamic pricing) of different qualities of service is unstable and extremely unlikely to reflect the correct price for the particular utility of the achieved service quality.
 
The point of that observation is that even a simple 2 classes of service system (so-called Paris Metro Pricing) is unstable, such that users of such a system will not be encouraged to set the priorities/service types to make system optimal or stable.
 
I can explain more, but the end user doesn't benefit from multiple choices of class of service at the packet level.
-----Original Message-----
From: "Jonathan Morton" <chromatix99@gmail.com>
Sent: Friday, March 15, 2019 3:32pm
To: "Mikael Abrahamsson" <swmike@swm.pp.se>
Cc: "David P. Reed" <dpreed@deepplum.com>, ecn-sane@lists.bufferbloat.net, "bloat" <bloat@lists.bufferbloat.net>
Subject: Re: [Bloat] [Ecn-sane] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104



> On 15 Mar, 2019, at 8:36 pm, Mikael Abrahamsson <swmike@swm.pp.se> wrote:
> 
> Having a "lower-than-best-effort" diffserve codepoint might work, because it means worse treatment, not preferential treatment.
> 
> The problem with having DSCP CPs that indicate preferential treatment is typically a ddos magnet.

This is true, and also why I feel that just 2 bits should be sufficient for Diffserv (rather than 6). They are sufficient to express four different optimisation targets:

0: Maximum Throughput (aka Best Effort)
1: Minimum Cost (aka Least Effort)
2: Minimum Latency (aka Maximum Responsiveness)
3: Minimum Loss (aka Maximum Reliability)

It is legitimate for traffic to request any of these four optimisations, with the explicit tradeoff of *not* necessarily getting optimisation in the other three dimensions.

The old TOS spec erred in specifying 4 non-exclusive bits to express this, in addition to 3 bits for a telegram-office style "priority level" (which was very much ripe for abuse if not strictly admission-controlled). TOS was rightly considered a mess, but was replaced with Diffserv which was far too loose a spec to be useful in practice.

But that's a separate topic from ECN per se.

 - Jonathan Morton


[-- Attachment #2: Type: text/html, Size: 3562 bytes --]

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Jonathan Morton]

> On 15 Mar, 2019, at 9:44 pm, David P. Reed <dpreed@deepplum.com> wrote:
> 
> pricing (even dynamic pricing) of different qualities of service is unstable

An interesting result, but I should note that the four-way optimisation system I described doesn't rely on pricing, only a sufficiently correct implementation of those optimisations at enough bottlenecks to make it worthwhile for applications to mark their traffic appropriately.  The technology exists to do so, but is not standardised in a way that makes it usable.

 - Jonathan Morton

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[David P. Reed]

[-- Attachment #1: Type: text/plain, Size: 3521 bytes --]


My point is that the argument for doing such balancing is that somehow ISPs at the entry points (representing somehow the goals of source and destination of each flow) will classify their flows correctly based on some criterion, and not select the option that allows them to "beat" all the others, which then causes them be "game theoreitically" incented to screw up the labeling.
 
The business argument that the users at both ends will choose the rignt labels is that they are responsive to price signals in a very sensitive way that will get them to mark things correctly. (that includes, by the way, the Internet Access Providers, if they take over the labeling job and force their choice on their users, because they become the "endpoint")
 
So if pricing mechanisms don't work to incent labeling correctly, it does not matter that there exists an optimum that can be achieved by an Oracle who fully decides the settings on all packets of all protocols ever to be invented.
 
And that's why I brought up the issue of pricing and economics, which sadly really affect any kind of queue management.
 
That's why pricing becomes a practical issue, and issues of "utility" to the users become important.
 
Now the other thing that is crucial is that the optimal state almost all of the time of every link in the network is that a utilization far from max capacity. The reason for this is the fact that the Internet (like almost all networks) is bursty and fractal. The law of large numbers doesn't smooth traffic volume over any timescale (that's the sense of fractalness here). There is no statistical smoothing of load - there are rare high peaks on some links but most links are underutilized, *if you want all the protocols currently used in the Internet to make users happy with minimal time-to-task-completion* (response time at the scale that matters for the particular user's needs at that moment).
 
So if most links are uncongested most of the time (and they should be if the folks maintaining the subnets are all doing their job by growing links that are congested to handle more traffic), then congestion management is only a peak load problem, and only affects things a small percentage of the time.
 
This is very, very different from the typical "benchmark" case, which focuses only on dealing with peak loads, which are transient in the real world. Most "benchmarks" make the strange and unrealistic assumption that overload is steady state, and that users themselves don't give up and stop using an overloaded system.
 
 
-----Original Message-----
From: "Jonathan Morton" <chromatix99@gmail.com>
Sent: Friday, March 15, 2019 4:13pm
To: "David P. Reed" <dpreed@deepplum.com>
Cc: "Mikael Abrahamsson" <swmike@swm.pp.se>, ecn-sane@lists.bufferbloat.net, "bloat" <bloat@lists.bufferbloat.net>
Subject: Re: [Bloat] [Ecn-sane] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104



> On 15 Mar, 2019, at 9:44 pm, David P. Reed <dpreed@deepplum.com> wrote:
> 
> pricing (even dynamic pricing) of different qualities of service is unstable

An interesting result, but I should note that the four-way optimisation system I described doesn't rely on pricing, only a sufficiently correct implementation of those optimisations at enough bottlenecks to make it worthwhile for applications to mark their traffic appropriately. The technology exists to do so, but is not standardised in a way that makes it usable.

 - Jonathan Morton


[-- Attachment #2: Type: text/html, Size: 5599 bytes --]

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Jonathan Morton]

> On 16 Mar, 2019, at 1:43 am, David P. Reed <dpreed@deepplum.com> wrote:
> 
> Now the other thing that is crucial is that the optimal state almost all of the time of every link in the network is that a utilization far from max capacity. The reason for this is the fact that the Internet (like almost all networks) is bursty and fractal.

That can be said about some types of links but not others.

Last-mile links in particular are often saturated by their users' individual traffic for minutes or even hours at a time, especially the slower link technologies such as ADSL and 4G.  The user wants their hundred-gigabyte game update installed as soon as possible, even if they only have 10Mbps to suck it through, and they still want to use their connection for other things while they wait.  And this is not unreasonable; I do it regularly.

At peak times, ISP backhaul capacity can often be enough of a bottleneck for users to notice the congestion and induced latency; it is far from the case that all ISPs worldwide massively over-provision their networks to avoid routine congestion, even in modern technologically advanced nations.  There are remote islands where hundreds or thousands of users must share a single satellite or microwave uplink.  Cell towers are also a shared medium with decidedly finite capacity.

Only core networks, and the backhaul networks of certain particularly conscientious ISPs, can typically be described as congestion-free.  And that is why we discuss AQM and ECN in such detail in the first place; without congestion, they wouldn't be required.

The extent to which traffic classification is needed on particular types of link can be debated.  It could fairly be argued that we've done remarkably well without the benefit of a functioning Diffserv ecosystem, so there is no particular urgency to create one.  At the same time, it's worth discussing *why* Diffserv fails to do its intended job, and how a better system *could* be designed, because that may reveal lessons for the future.

I will say this: there are times, even with the benefit of everything Cake does for me, when I would prefer that BitTorrent traffic would automatically defer to other stuff (as it was supposedly designed to).  Several game updaters, including Wargaming.net's, use BitTorrent under the skin - opening and using several hundred flows in parallel, and thereby swamping any other traffic going to the same host.  It would be very straightforward for them to mark all that traffic as Minimum Cost, while their games themselves use Minimum Latency for battle traffic.

Minimum Cost is a natural choice for any transport using LEDBAT, or with similarly altruistic philosophy.

Minimum Latency is a natural choice for any application requiring realtime response - games, VoIP, remote shells.

Minimum Loss is a natural choice for applications involved in network control, where dropped packets could have a much greater than normal impact on overall network performance.

Maximum Throughput is a natural choice for general-purpose applications not fitting any of the above.

Pricing is not required.  Making the wrong choice will simply make your application perform badly on a loaded network, as the bottleneck link optimises for the thing you told it to optimise for, rather than for what you actually want.  That's all that's really needed.

 - Jonathan Morton

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Sebastian Moeller]

Hi Dave,

On March 16, 2019 12:43:58 AM GMT+01:00, "David P. Reed" <dpreed@deepplum.com> wrote:
>
>My point is that the argument for doing such balancing is that somehow
>ISPs at the entry points (representing somehow the goals of source and
>destination of each flow) will classify their flows correctly based on
>some criterion, and not select the option that allows them to "beat"
>all the others, which then causes them be "game theoreitically"
>incented to screw up the labeling.

One more argument for splitting the 6 dscp bits, one half for the ISP one half for end to end signalling...
I do neither expect ISPs to honor the intent bits (with the possible exception of the LE patter, there e2e and ISP goals seem aligned) and I also do not see any approach gain traction that completely takes the dscp bits away from the intermediate transports, whether one likes it or not, these effectively are under transport control and are actually used, so hoping the current owner giving all of them back seems overly optimistic. Hence the 50/50 split.


> 
>The business argument that the users at both ends will choose the rignt
>labels is that they are responsive to price signals in a very sensitive
>way that will get them to mark things correctly.

Right or wrong, or how to interpret the different pattern is a question that only becomes relevant once the patterns are signalled robustly end to end...

 (that includes, by the
>way, the Internet Access Providers, if they take over the labeling job
>and force their choice on their users, because they become the
>"endpoint")

Not with the split proposal, and yes end users depend on their ISP doing reasonable traffic management, but that seems orthogonal to dscp bit patterns to me.

> 
>So if pricing mechanisms don't work to incent labeling correctly, it
>does not matter that there exists an optimum that can be achieved by an
>Oracle who fully decides the settings on all packets of all protocols
>ever to be invented.
> 
>And that's why I brought up the issue of pricing and economics, which
>sadly really affect any kind of queue management.

Sure in the context of hoping the ISPs and the wider internet respecting endpoint set dscps that seems all applicable.

> 
>That's why pricing becomes a practical issue, and issues of "utility"
>to the users become important.
> 
>Now the other thing that is crucial is that the optimal state almost
>all of the time of every link in the network is that a utilization far
>from max capacity. The reason for this is the fact that the Internet
>(like almost all networks) is bursty and fractal. The law of large
>numbers doesn't smooth traffic volume over any timescale (that's the
>sense of fractalness here). There is no statistical smoothing of load -
>there are rare high peaks on some links but most links are
>underutilized, *if you want all the protocols currently used in the
>Internet to make users happy with minimal time-to-task-completion*
>(response time at the scale that matters for the particular user's
>needs at that moment).
> 
>So if most links are uncongested most of the time (and they should be
>if the folks maintaining the subnets are all doing their job by growing
>links that are congested to handle more traffic), then congestion
>management is only a peak load problem, and only affects things a small
>percentage of the time.

I concur with Jonathan, access links often run much closer to their limit than core networks, and the whole bufferbloat project demonstrated that a capable AQM system with mild tiering can make a saturated link still acceptable to use even for low latency applications...
But for ingress shaping it would be really great to have some trustworthy way of deducing the sender's intent, and dscps seem like a natural fit.

Best Regards
          Sebastian


> 
>This is very, very different from the typical "benchmark" case, which
>focuses only on dealing with peak loads, which are transient in the
>real world. Most "benchmarks" make the strange and unrealistic
>assumption that overload is steady state, and that users themselves
>don't give up and stop using an overloaded system.



> 
> 
>-----Original Message-----
>From: "Jonathan Morton" <chromatix99@gmail.com>
>Sent: Friday, March 15, 2019 4:13pm
>To: "David P. Reed" <dpreed@deepplum.com>
>Cc: "Mikael Abrahamsson" <swmike@swm.pp.se>,
>ecn-sane@lists.bufferbloat.net, "bloat" <bloat@lists.bufferbloat.net>
>Subject: Re: [Bloat] [Ecn-sane] [iccrg] Fwd: [tcpPrague] Implementation
>and experimentation of TCP Prague/L4S hackaton at IETF104
>
>
>
>> On 15 Mar, 2019, at 9:44 pm, David P. Reed <dpreed@deepplum.com>
>wrote:
>> 
>> pricing (even dynamic pricing) of different qualities of service is
>unstable
>
>An interesting result, but I should note that the four-way optimisation
>system I described doesn't rely on pricing, only a sufficiently correct
>implementation of those optimisations at enough bottlenecks to make it
>worthwhile for applications to mark their traffic appropriately. The
>technology exists to do so, but is not standardised in a way that makes
>it usable.
>
> - Jonathan Morton

-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Michael Richardson]

[-- Attachment #1: Type: text/plain, Size: 728 bytes --]


The DSCP code points were also supposed to be local to the AS.
They are *supposed* to be recoded at the edges.

What is missing the diffedge protocol... MS actually implemented this in Win2K.
We have no way to signal the ToS we desire with the ISP, and so they are
forced to guess, and they do it wrong.

I actually see this as the critical NetNeutrality issue.  We *DO*
want multiple classes of services, but we want to be in charge of
what traffic goes into each class, not the ISP.

--
]               Never tell me the odds!                 | ipv6 mesh networks [
]   Michael Richardson, Sandelman Software Works        |    IoT architect   [
]     mcr@sandelman.ca  http://www.sandelman.ca/        |   ruby on rails    [


[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 487 bytes --]

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Jonathan Foulkes]

All this discussion of DSCP marking brings to mind what happened on the Windows platform, where the OS had to suppress ALL DSCP marks, as app authors were trying to game the system.
And even if not trying to ‘game’ it, they have non-obvious reasons why they don’t mark traffic how one would expect. Example:

I know an engineer who works at a cloud-storage solution company, and I asked why a long-standing customer request for DSCP marking (as bulk) was not implemented. His answer was they’d never do that, as that would impact benchmarks against their competitors for which service syncs faster. <sigh>

Which brings me to a question: Is anyone aware of an easy to use Windows app that will allow the user to select an application and tell the OS to mark the traffic (all or by port) with a user selected DSCP level?
There are many guides on using regedit and other error-prone (and geek-only) means of doing this, but is there a simple Windows 10 home app?

Now that Cake is out there with simple DiffServ3 support, it would be nice to lower the priority of cloud-storage services and other bulk traffic by correctly marking it at the origin. 

Cheers,

Jonathan Foulkes


> On Mar 15, 2019, at 3:32 PM, Jonathan Morton <chromatix99@gmail.com> wrote:
> 
>> On 15 Mar, 2019, at 8:36 pm, Mikael Abrahamsson <swmike@swm.pp.se> wrote:
>> 
>> Having a "lower-than-best-effort" diffserve codepoint might work, because it means worse treatment, not preferential treatment.
>> 
>> The problem with having DSCP CPs that indicate preferential treatment is typically a ddos magnet.
> 
> This is true, and also why I feel that just 2 bits should be sufficient for Diffserv (rather than 6).  They are sufficient to express four different optimisation targets:
> 
> 0: Maximum Throughput (aka Best Effort)
> 1: Minimum Cost (aka Least Effort)
> 2: Minimum Latency (aka Maximum Responsiveness)
> 3: Minimum Loss (aka Maximum Reliability)
> 
> It is legitimate for traffic to request any of these four optimisations, with the explicit tradeoff of *not* necessarily getting optimisation in the other three dimensions.
> 
> The old TOS spec erred in specifying 4 non-exclusive bits to express this, in addition to 3 bits for a telegram-office style "priority level" (which was very much ripe for abuse if not strictly admission-controlled).  TOS was rightly considered a mess, but was replaced with Diffserv which was far too loose a spec to be useful in practice.
> 
> But that's a separate topic from ECN per se.
> 
> - Jonathan Morton
> 
> _______________________________________________
> Bloat mailing list
> Bloat@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/bloat

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Dave Taht]

On Fri, Mar 15, 2019 at 1:28 PM Jonathan Foulkes <jf@jonathanfoulkes.com> wrote:
>
> All this discussion of DSCP marking brings to mind what happened on the Windows platform, where the OS had to suppress ALL DSCP marks, as app authors were trying to game the system.
> And even if not trying to ‘game’ it, they have non-obvious reasons why they don’t mark traffic how one would expect. Example:
>
> I know an engineer who works at a cloud-storage solution company, and I asked why a long-standing customer request for DSCP marking (as bulk) was not implemented. His answer was they’d never do that, as that would impact benchmarks against their competitors for which service syncs faster. <sigh>
>
> Which brings me to a question: Is anyone aware of an easy to use Windows app that will allow the user to select an application and tell the OS to mark the traffic (all or by port) with a user selected DSCP level?
> There are many guides on using regedit and other error-prone (and geek-only) means of doing this, but is there a simple Windows 10 home app?

When I last tried it (years ago), in order to set the tos bits, an
application merely had to have admin privs.

> Now that Cake is out there with simple DiffServ3 support, it would be nice to lower the priority of cloud-storage services and other bulk traffic by correctly marking it at the origin.
>
> Cheers,
>
> Jonathan Foulkes
>
>
> > On Mar 15, 2019, at 3:32 PM, Jonathan Morton <chromatix99@gmail.com> wrote:
> >
> >> On 15 Mar, 2019, at 8:36 pm, Mikael Abrahamsson <swmike@swm.pp.se> wrote:
> >>
> >> Having a "lower-than-best-effort" diffserve codepoint might work, because it means worse treatment, not preferential treatment.
> >>
> >> The problem with having DSCP CPs that indicate preferential treatment is typically a ddos magnet.
> >
> > This is true, and also why I feel that just 2 bits should be sufficient for Diffserv (rather than 6).  They are sufficient to express four different optimisation targets:
> >
> > 0: Maximum Throughput (aka Best Effort)
> > 1: Minimum Cost (aka Least Effort)
> > 2: Minimum Latency (aka Maximum Responsiveness)
> > 3: Minimum Loss (aka Maximum Reliability)
> >
> > It is legitimate for traffic to request any of these four optimisations, with the explicit tradeoff of *not* necessarily getting optimisation in the other three dimensions.
> >
> > The old TOS spec erred in specifying 4 non-exclusive bits to express this, in addition to 3 bits for a telegram-office style "priority level" (which was very much ripe for abuse if not strictly admission-controlled).  TOS was rightly considered a mess, but was replaced with Diffserv which was far too loose a spec to be useful in practice.
> >
> > But that's a separate topic from ECN per se.
> >
> > - Jonathan Morton
> >
> > _______________________________________________
> > Bloat mailing list
> > Bloat@lists.bufferbloat.net
> > https://lists.bufferbloat.net/listinfo/bloat
>
> _______________________________________________
> Bloat mailing list
> Bloat@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/bloat



-- 

Dave Täht
CTO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-831-205-9740

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[David P. Reed]

[-- Attachment #1: Type: text/plain, Size: 3854 bytes --]


How many applications used by normal users have "admin" privileges? The Browser? Email? FTP?
 
 
-----Original Message-----
From: "Dave Taht" <dave.taht@gmail.com>
Sent: Friday, March 15, 2019 4:31pm
To: "Jonathan Foulkes" <jf@jonathanfoulkes.com>
Cc: ecn-sane@lists.bufferbloat.net, "bloat" <bloat@lists.bufferbloat.net>
Subject: Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104



On Fri, Mar 15, 2019 at 1:28 PM Jonathan Foulkes <jf@jonathanfoulkes.com> wrote:
>
> All this discussion of DSCP marking brings to mind what happened on the Windows platform, where the OS had to suppress ALL DSCP marks, as app authors were trying to game the system.
> And even if not trying to ‘game’ it, they have non-obvious reasons why they don’t mark traffic how one would expect. Example:
>
> I know an engineer who works at a cloud-storage solution company, and I asked why a long-standing customer request for DSCP marking (as bulk) was not implemented. His answer was they’d never do that, as that would impact benchmarks against their competitors for which service syncs faster. <sigh>
>
> Which brings me to a question: Is anyone aware of an easy to use Windows app that will allow the user to select an application and tell the OS to mark the traffic (all or by port) with a user selected DSCP level?
> There are many guides on using regedit and other error-prone (and geek-only) means of doing this, but is there a simple Windows 10 home app?

When I last tried it (years ago), in order to set the tos bits, an
application merely had to have admin privs.

> Now that Cake is out there with simple DiffServ3 support, it would be nice to lower the priority of cloud-storage services and other bulk traffic by correctly marking it at the origin.
>
> Cheers,
>
> Jonathan Foulkes
>
>
> > On Mar 15, 2019, at 3:32 PM, Jonathan Morton <chromatix99@gmail.com> wrote:
> >
> >> On 15 Mar, 2019, at 8:36 pm, Mikael Abrahamsson <swmike@swm.pp.se> wrote:
> >>
> >> Having a "lower-than-best-effort" diffserve codepoint might work, because it means worse treatment, not preferential treatment.
> >>
> >> The problem with having DSCP CPs that indicate preferential treatment is typically a ddos magnet.
> >
> > This is true, and also why I feel that just 2 bits should be sufficient for Diffserv (rather than 6). They are sufficient to express four different optimisation targets:
> >
> > 0: Maximum Throughput (aka Best Effort)
> > 1: Minimum Cost (aka Least Effort)
> > 2: Minimum Latency (aka Maximum Responsiveness)
> > 3: Minimum Loss (aka Maximum Reliability)
> >
> > It is legitimate for traffic to request any of these four optimisations, with the explicit tradeoff of *not* necessarily getting optimisation in the other three dimensions.
> >
> > The old TOS spec erred in specifying 4 non-exclusive bits to express this, in addition to 3 bits for a telegram-office style "priority level" (which was very much ripe for abuse if not strictly admission-controlled). TOS was rightly considered a mess, but was replaced with Diffserv which was far too loose a spec to be useful in practice.
> >
> > But that's a separate topic from ECN per se.
> >
> > - Jonathan Morton
> >
> > _______________________________________________
> > Bloat mailing list
> > Bloat@lists.bufferbloat.net
> > https://lists.bufferbloat.net/listinfo/bloat
>
> _______________________________________________
> Bloat mailing list
> Bloat@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/bloat



-- 

Dave Täht
CTO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-831-205-9740
_______________________________________________
Ecn-sane mailing list
Ecn-sane@lists.bufferbloat.net
https://lists.bufferbloat.net/listinfo/ecn-sane

[-- Attachment #2: Type: text/html, Size: 4989 bytes --]

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Michael Welzl]

[-- Attachment #1: Type: text/plain, Size: 4495 bytes --]

Good question!  …. on Windows in particular, I’d really like to know this too.

The WebRTC Javascript API allows one to influence the DSCP, i.e. browsers normally can do that. Whether that’s true for all OSes, I don’t know.

Cheers,
Michael



> On Mar 16, 2019, at 12:45 AM, David P. Reed <dpreed@deepplum.com> wrote:
> 
> How many applications used by normal users have "admin" privileges? The Browser? Email? FTP?
>  
>  
> -----Original Message-----
> From: "Dave Taht" <dave.taht@gmail.com>
> Sent: Friday, March 15, 2019 4:31pm
> To: "Jonathan Foulkes" <jf@jonathanfoulkes.com>
> Cc: ecn-sane@lists.bufferbloat.net, "bloat" <bloat@lists.bufferbloat.net>
> Subject: Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104
> 
> On Fri, Mar 15, 2019 at 1:28 PM Jonathan Foulkes <jf@jonathanfoulkes.com> wrote:
> >
> > All this discussion of DSCP marking brings to mind what happened on the Windows platform, where the OS had to suppress ALL DSCP marks, as app authors were trying to game the system.
> > And even if not trying to ‘game’ it, they have non-obvious reasons why they don’t mark traffic how one would expect. Example:
> >
> > I know an engineer who works at a cloud-storage solution company, and I asked why a long-standing customer request for DSCP marking (as bulk) was not implemented. His answer was they’d never do that, as that would impact benchmarks against their competitors for which service syncs faster. <sigh>
> >
> > Which brings me to a question: Is anyone aware of an easy to use Windows app that will allow the user to select an application and tell the OS to mark the traffic (all or by port) with a user selected DSCP level?
> > There are many guides on using regedit and other error-prone (and geek-only) means of doing this, but is there a simple Windows 10 home app?
> 
> When I last tried it (years ago), in order to set the tos bits, an
> application merely had to have admin privs.
> 
> > Now that Cake is out there with simple DiffServ3 support, it would be nice to lower the priority of cloud-storage services and other bulk traffic by correctly marking it at the origin.
> >
> > Cheers,
> >
> > Jonathan Foulkes
> >
> >
> > > On Mar 15, 2019, at 3:32 PM, Jonathan Morton <chromatix99@gmail.com> wrote:
> > >
> > >> On 15 Mar, 2019, at 8:36 pm, Mikael Abrahamsson <swmike@swm.pp.se> wrote:
> > >>
> > >> Having a "lower-than-best-effort" diffserve codepoint might work, because it means worse treatment, not preferential treatment.
> > >>
> > >> The problem with having DSCP CPs that indicate preferential treatment is typically a ddos magnet.
> > >
> > > This is true, and also why I feel that just 2 bits should be sufficient for Diffserv (rather than 6). They are sufficient to express four different optimisation targets:
> > >
> > > 0: Maximum Throughput (aka Best Effort)
> > > 1: Minimum Cost (aka Least Effort)
> > > 2: Minimum Latency (aka Maximum Responsiveness)
> > > 3: Minimum Loss (aka Maximum Reliability)
> > >
> > > It is legitimate for traffic to request any of these four optimisations, with the explicit tradeoff of *not* necessarily getting optimisation in the other three dimensions.
> > >
> > > The old TOS spec erred in specifying 4 non-exclusive bits to express this, in addition to 3 bits for a telegram-office style "priority level" (which was very much ripe for abuse if not strictly admission-controlled). TOS was rightly considered a mess, but was replaced with Diffserv which was far too loose a spec to be useful in practice.
> > >
> > > But that's a separate topic from ECN per se.
> > >
> > > - Jonathan Morton
> > >
> > > _______________________________________________
> > > Bloat mailing list
> > > Bloat@lists.bufferbloat.net
> > > https://lists.bufferbloat.net/listinfo/bloat
> >
> > _______________________________________________
> > Bloat mailing list
> > Bloat@lists.bufferbloat.net
> > https://lists.bufferbloat.net/listinfo/bloat
> 
> 
> 
> -- 
> 
> Dave Täht
> CTO, TekLibre, LLC
> http://www.teklibre.com
> Tel: 1-831-205-9740
> _______________________________________________
> Ecn-sane mailing list
> Ecn-sane@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/ecn-sane
> _______________________________________________
> Bloat mailing list
> Bloat@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/bloat


[-- Attachment #2: Type: text/html, Size: 7448 bytes --]

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Sebastian Moeller]

> On Mar 16, 2019, at 10:42, Michael Welzl <michawe@ifi.uio.no> wrote:
> 
> Good question!  …. on Windows in particular, I’d really like to know this too.

	Well, as far as I can tell it is the group policy editor that is the tool to assign DSCPs to applications, IMHO that is exactly the right place, somewhere where the administrator/enduser can set her desired policy (personally I am fine with applications also using sensible defaults, as long as the user can override them all is well). The catch seems to be that group policies require a domain controller and are hence not available on stand-alond windows home installations. Anybody with deep contacts to microsoft here, that could try to get an sub-official standpoint from MS on the issue of opening the group policy editor up for everybody (at least the dscp marking part)?

Best Regards
	Sebastian


> 
> The WebRTC Javascript API allows one to influence the DSCP, i.e. browsers normally can do that. Whether that’s true for all OSes, I don’t know.
> 
> Cheers,
> Michael
> 
> 
> 
>> On Mar 16, 2019, at 12:45 AM, David P. Reed <dpreed@deepplum.com> wrote:
>> 
>> How many applications used by normal users have "admin" privileges? The Browser? Email? FTP?
>>  
>>  
>> -----Original Message-----
>> From: "Dave Taht" <dave.taht@gmail.com>
>> Sent: Friday, March 15, 2019 4:31pm
>> To: "Jonathan Foulkes" <jf@jonathanfoulkes.com>
>> Cc: ecn-sane@lists.bufferbloat.net, "bloat" <bloat@lists.bufferbloat.net>
>> Subject: Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104
>> 
>> On Fri, Mar 15, 2019 at 1:28 PM Jonathan Foulkes <jf@jonathanfoulkes.com> wrote:
>> >
>> > All this discussion of DSCP marking brings to mind what happened on the Windows platform, where the OS had to suppress ALL DSCP marks, as app authors were trying to game the system.
>> > And even if not trying to ‘game’ it, they have non-obvious reasons why they don’t mark traffic how one would expect. Example:
>> >
>> > I know an engineer who works at a cloud-storage solution company, and I asked why a long-standing customer request for DSCP marking (as bulk) was not implemented. His answer was they’d never do that, as that would impact benchmarks against their competitors for which service syncs faster. <sigh>
>> >
>> > Which brings me to a question: Is anyone aware of an easy to use Windows app that will allow the user to select an application and tell the OS to mark the traffic (all or by port) with a user selected DSCP level?
>> > There are many guides on using regedit and other error-prone (and geek-only) means of doing this, but is there a simple Windows 10 home app?
>> 
>> When I last tried it (years ago), in order to set the tos bits, an
>> application merely had to have admin privs.
>> 
>> > Now that Cake is out there with simple DiffServ3 support, it would be nice to lower the priority of cloud-storage services and other bulk traffic by correctly marking it at the origin.
>> >
>> > Cheers,
>> >
>> > Jonathan Foulkes
>> >
>> >
>> > > On Mar 15, 2019, at 3:32 PM, Jonathan Morton <chromatix99@gmail.com> wrote:
>> > >
>> > >> On 15 Mar, 2019, at 8:36 pm, Mikael Abrahamsson <swmike@swm.pp.se> wrote:
>> > >>
>> > >> Having a "lower-than-best-effort" diffserve codepoint might work, because it means worse treatment, not preferential treatment.
>> > >>
>> > >> The problem with having DSCP CPs that indicate preferential treatment is typically a ddos magnet.
>> > >
>> > > This is true, and also why I feel that just 2 bits should be sufficient for Diffserv (rather than 6). They are sufficient to express four different optimisation targets:
>> > >
>> > > 0: Maximum Throughput (aka Best Effort)
>> > > 1: Minimum Cost (aka Least Effort)
>> > > 2: Minimum Latency (aka Maximum Responsiveness)
>> > > 3: Minimum Loss (aka Maximum Reliability)
>> > >
>> > > It is legitimate for traffic to request any of these four optimisations, with the explicit tradeoff of *not* necessarily getting optimisation in the other three dimensions.
>> > >
>> > > The old TOS spec erred in specifying 4 non-exclusive bits to express this, in addition to 3 bits for a telegram-office style "priority level" (which was very much ripe for abuse if not strictly admission-controlled). TOS was rightly considered a mess, but was replaced with Diffserv which was far too loose a spec to be useful in practice.
>> > >
>> > > But that's a separate topic from ECN per se.
>> > >
>> > > - Jonathan Morton
>> > >
>> > > _______________________________________________
>> > > Bloat mailing list
>> > > Bloat@lists.bufferbloat.net
>> > > https://lists.bufferbloat.net/listinfo/bloat
>> >
>> > _______________________________________________
>> > Bloat mailing list
>> > Bloat@lists.bufferbloat.net
>> > https://lists.bufferbloat.net/listinfo/bloat
>> 
>> 
>> 
>> -- 
>> 
>> Dave Täht
>> CTO, TekLibre, LLC
>> http://www.teklibre.com
>> Tel: 1-831-205-9740
>> _______________________________________________
>> Ecn-sane mailing list
>> Ecn-sane@lists.bufferbloat.net
>> https://lists.bufferbloat.net/listinfo/ecn-sane
>> _______________________________________________
>> Bloat mailing list
>> Bloat@lists.bufferbloat.net
>> https://lists.bufferbloat.net/listinfo/bloat
> 
> _______________________________________________
> Bloat mailing list
> Bloat@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/bloat

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Nils Andreas Svee]

You can use group policies on standalone clients, however the Local Group Policy Editor is not available on the Windows Home editions (neither is domain membership AFAIK), and so many people resort to applying the changes they require directly to the registry.

There are also tools like Policy Plus that allows you to edit local GPOs regardless of which edition of Windows you are running , but I haven't tried it myself: https://github.com/Fleex255/PolicyPlus

Best Regards
Nils

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Jonathan Foulkes]

Thanks Nils, I’d seen that PolicyPlus tool before, and while a nice stand-alone option for any Windows version, it is still a tool for admins. I think we need something regular technical users can use to do things like ‘Make DropBox traffic land in the bulk tin’.

Also, there is a good thread about other mechanisms to route traffic into the bulk tin using rules in the router here: https://github.com/dtaht/sch_cake/issues/97  Including a documented approach to setting windows DSCP settings via PowerShell.

Cheers,

Jonathan Foulkes

> On Mar 16, 2019, at 6:23 AM, Nils Andreas Svee <me@lochnair.net> wrote:
> 
> You can use group policies on standalone clients, however the Local Group Policy Editor is not available on the Windows Home editions (neither is domain membership AFAIK), and so many people resort to applying the changes they require directly to the registry.
> 
> There are also tools like Policy Plus that allows you to edit local GPOs regardless of which edition of Windows you are running , but I haven't tried it myself: https://github.com/Fleex255/PolicyPlus
> 
> Best Regards
> Nils
> _______________________________________________
> Bloat mailing list
> Bloat@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/bloat

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Holland, Jake]

On 2019-03-15, 11:37, "Mikael Abrahamsson" <swmike@swm.pp.se> wrote:
    L4S has a much better possibility of actually getting deployment into the 
    wider Internet packet-moving equipment than anything being talked about 
    here. Same with PIE as opposed to FQ_CODEL. I know it's might not be as 
    good, but it fits better into actual silicon and it's being proposed by 
    people who actually have better channels into the people setting hard 
    requirements.
    
    I suggest you consider joining them instead of opposing them.


Hi Mikael,

I agree it makes sense that fq_anything has issues when you're talking
about the OLT/CMTS/BNG/etc., and I believe it when you tell me PIE
makes better sense there.

But fq_x makes great sense and provides real value for the uplink in a
home, small office, coffee shop, etc. (if you run the final rate limit
on the home side of the access link.)  I'm thinking maybe there's a
disconnect here driven by the different use cases for where AQMs can go.

The thing is, each of these is the most likely congestion point at
different times, and it's worthwhile for each of them to be able to
AQM (and mark packets) under congestion.

One of the several things that bothers me with L4S is that I've seen
precious little concern over interfering with the ability for another
different AQM in-path to mark packets, and because it changes the
semantics of CE, you can't have both working at the same time unless
they both do L4S.

SCE needs a lot of details filled in, but it's so much cleaner that it
seems to me there's reasonably obvious answers to all (or almost all) of
those detail questions, and because the semantics are so much cleaner,
it's much easier to tell it's non-harmful.

<aside regarding="non-harmful">
The point you raised in another thread about reordering is mostly
well-taken, and a good counterpoint to the claim "non-harmful relative
to L4S".

To me it seems sad and dumb that switches ended up trying to make
ordering guarantees at cost of switching performance, because if it's
useful to put ordering in the switch, then it must be equally useful to
put it in the receiver's NIC or OS.

So why isn't it in all the receivers' NIC or OS (where it would render
the switch's ordering efforts moot) instead of in all the switches?

I'm guessing the answer is a competition trap for the switch vendors,
plus "with ordering goes faster than without, when you benchmark the
switch with typical load and current (non-RACK) receivers".

If that's the case, it seems like the drive for a competitive advantage
caused deployment of a packet ordering workaround in the wrong network
location(s), out of a pure misalignment of incentives.

RACK rates to fix that in the end, but a lot of damage is already done,
and the L4S approach gives switches a flag that can double as proof that
RACK is there on the receiver, so they can stop trying to order those
packets.

So point granted, I understand and agree there's a cost to abandoning
that advantage.
</aside>

But as you also said so well in another thread, this is important.  ("The
last unicorn", IIRC.)  How much does it matter if there's a feature that
has value today, but only until RACK is widely deployed?  If you were
convinced RACK would roll out everywhere within 3 years and SCE would
produce better results than L4S over the following 15 years, would that
change your mind?

It would for me, and that's why I'd like to see SCE explored before
making a call.  I think at its core, it provides the same thing L4S does
(a high-fidelity explicit congestion signal for the sender), but with
much cleaner semantics that can be incrementally added to congestion
controls that people are already using.

Granted, it still remains to be seen whether SCE in practice can match
the results of L4S, and L4S was here first.  But it seems to me L4S comes
with some problems that have not yet been examined, and that are nicely
dodged by a SCE-based approach.

If L4S really is as good as they seem to think, I could imagine getting
behind it, but I don't think that's proven yet.  I'm not certain, but
all the comparative analyses I remember seeing have been from more or
less the same team, and I'm not convinced they don't have some
misaligned incentives of their own.

I understand a lot of work has gone into L4S, but this move to jump it
from interesting experiment to de-facto standard without a more critical
review that digs deeper into some of the potential deployment problems
has me concerned.

If it really does turn out to be good enough to be permanent, I'm not
opposed to it, but I'm just not convinced that it's non-harmful, and my
default position is that the cleaner solution is going to be better in
the long run, if they can do the same job.

It's not that I want it to be a fight, but I do want to end up with the
best solution we can get.  We only have the one internet.

Just my 2c.  

-Jake

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Vint Cerf]

[-- Attachment #1: Type: text/plain, Size: 5471 bytes --]

where does BBR fit into all this?

v


On Sat, Mar 16, 2019 at 5:39 PM Holland, Jake <jholland@akamai.com> wrote:

> On 2019-03-15, 11:37, "Mikael Abrahamsson" <swmike@swm.pp.se> wrote:
>     L4S has a much better possibility of actually getting deployment into
> the
>     wider Internet packet-moving equipment than anything being talked
> about
>     here. Same with PIE as opposed to FQ_CODEL. I know it's might not be
> as
>     good, but it fits better into actual silicon and it's being proposed
> by
>     people who actually have better channels into the people setting hard
>     requirements.
>
>     I suggest you consider joining them instead of opposing them.
>
>
> Hi Mikael,
>
> I agree it makes sense that fq_anything has issues when you're talking
> about the OLT/CMTS/BNG/etc., and I believe it when you tell me PIE
> makes better sense there.
>
> But fq_x makes great sense and provides real value for the uplink in a
> home, small office, coffee shop, etc. (if you run the final rate limit
> on the home side of the access link.)  I'm thinking maybe there's a
> disconnect here driven by the different use cases for where AQMs can go.
>
> The thing is, each of these is the most likely congestion point at
> different times, and it's worthwhile for each of them to be able to
> AQM (and mark packets) under congestion.
>
> One of the several things that bothers me with L4S is that I've seen
> precious little concern over interfering with the ability for another
> different AQM in-path to mark packets, and because it changes the
> semantics of CE, you can't have both working at the same time unless
> they both do L4S.
>
> SCE needs a lot of details filled in, but it's so much cleaner that it
> seems to me there's reasonably obvious answers to all (or almost all) of
> those detail questions, and because the semantics are so much cleaner,
> it's much easier to tell it's non-harmful.
>
> <aside regarding="non-harmful">
> The point you raised in another thread about reordering is mostly
> well-taken, and a good counterpoint to the claim "non-harmful relative
> to L4S".
>
> To me it seems sad and dumb that switches ended up trying to make
> ordering guarantees at cost of switching performance, because if it's
> useful to put ordering in the switch, then it must be equally useful to
> put it in the receiver's NIC or OS.
>
> So why isn't it in all the receivers' NIC or OS (where it would render
> the switch's ordering efforts moot) instead of in all the switches?
>
> I'm guessing the answer is a competition trap for the switch vendors,
> plus "with ordering goes faster than without, when you benchmark the
> switch with typical load and current (non-RACK) receivers".
>
> If that's the case, it seems like the drive for a competitive advantage
> caused deployment of a packet ordering workaround in the wrong network
> location(s), out of a pure misalignment of incentives.
>
> RACK rates to fix that in the end, but a lot of damage is already done,
> and the L4S approach gives switches a flag that can double as proof that
> RACK is there on the receiver, so they can stop trying to order those
> packets.
>
> So point granted, I understand and agree there's a cost to abandoning
> that advantage.
> </aside>
>
> But as you also said so well in another thread, this is important.  ("The
> last unicorn", IIRC.)  How much does it matter if there's a feature that
> has value today, but only until RACK is widely deployed?  If you were
> convinced RACK would roll out everywhere within 3 years and SCE would
> produce better results than L4S over the following 15 years, would that
> change your mind?
>
> It would for me, and that's why I'd like to see SCE explored before
> making a call.  I think at its core, it provides the same thing L4S does
> (a high-fidelity explicit congestion signal for the sender), but with
> much cleaner semantics that can be incrementally added to congestion
> controls that people are already using.
>
> Granted, it still remains to be seen whether SCE in practice can match
> the results of L4S, and L4S was here first.  But it seems to me L4S comes
> with some problems that have not yet been examined, and that are nicely
> dodged by a SCE-based approach.
>
> If L4S really is as good as they seem to think, I could imagine getting
> behind it, but I don't think that's proven yet.  I'm not certain, but
> all the comparative analyses I remember seeing have been from more or
> less the same team, and I'm not convinced they don't have some
> misaligned incentives of their own.
>
> I understand a lot of work has gone into L4S, but this move to jump it
> from interesting experiment to de-facto standard without a more critical
> review that digs deeper into some of the potential deployment problems
> has me concerned.
>
> If it really does turn out to be good enough to be permanent, I'm not
> opposed to it, but I'm just not convinced that it's non-harmful, and my
> default position is that the cleaner solution is going to be better in
> the long run, if they can do the same job.
>
> It's not that I want it to be a fight, but I do want to end up with the
> best solution we can get.  We only have the one internet.
>
> Just my 2c.
>
> -Jake
>
>
> _______________________________________________
> Ecn-sane mailing list
> Ecn-sane@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/ecn-sane
>


-- 
New postal address:
Google
1875 Explorer Street, 10th Floor
Reston, VA 20190

[-- Attachment #2: Type: text/html, Size: 6717 bytes --]

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Dave Taht]

Dear Vint:

BBR, along with all "non ect_1 sending L4S compatable" transports,
gets relegated to the dualpi  "Classic" queue.

https://datatracker.ietf.org/doc/draft-ietf-tsvwg-aqm-dualq-coupled/

On Sat, Mar 16, 2019 at 2:57 PM Vint Cerf <vint@google.com> wrote:
>
> where does BBR fit into all this?
>
> v
>
>
> On Sat, Mar 16, 2019 at 5:39 PM Holland, Jake <jholland@akamai.com> wrote:
>>
>> On 2019-03-15, 11:37, "Mikael Abrahamsson" <swmike@swm.pp.se> wrote:
>>     L4S has a much better possibility of actually getting deployment into the
>>     wider Internet packet-moving equipment than anything being talked about
>>     here. Same with PIE as opposed to FQ_CODEL. I know it's might not be as
>>     good, but it fits better into actual silicon and it's being proposed by
>>     people who actually have better channels into the people setting hard
>>     requirements.
>>
>>     I suggest you consider joining them instead of opposing them.
>>
>>
>> Hi Mikael,
>>
>> I agree it makes sense that fq_anything has issues when you're talking
>> about the OLT/CMTS/BNG/etc., and I believe it when you tell me PIE
>> makes better sense there.
>>
>> But fq_x makes great sense and provides real value for the uplink in a
>> home, small office, coffee shop, etc. (if you run the final rate limit
>> on the home side of the access link.)  I'm thinking maybe there's a
>> disconnect here driven by the different use cases for where AQMs can go.
>>
>> The thing is, each of these is the most likely congestion point at
>> different times, and it's worthwhile for each of them to be able to
>> AQM (and mark packets) under congestion.
>>
>> One of the several things that bothers me with L4S is that I've seen
>> precious little concern over interfering with the ability for another
>> different AQM in-path to mark packets, and because it changes the
>> semantics of CE, you can't have both working at the same time unless
>> they both do L4S.
>>
>> SCE needs a lot of details filled in, but it's so much cleaner that it
>> seems to me there's reasonably obvious answers to all (or almost all) of
>> those detail questions, and because the semantics are so much cleaner,
>> it's much easier to tell it's non-harmful.
>>
>> <aside regarding="non-harmful">
>> The point you raised in another thread about reordering is mostly
>> well-taken, and a good counterpoint to the claim "non-harmful relative
>> to L4S".
>>
>> To me it seems sad and dumb that switches ended up trying to make
>> ordering guarantees at cost of switching performance, because if it's
>> useful to put ordering in the switch, then it must be equally useful to
>> put it in the receiver's NIC or OS.
>>
>> So why isn't it in all the receivers' NIC or OS (where it would render
>> the switch's ordering efforts moot) instead of in all the switches?
>>
>> I'm guessing the answer is a competition trap for the switch vendors,
>> plus "with ordering goes faster than without, when you benchmark the
>> switch with typical load and current (non-RACK) receivers".
>>
>> If that's the case, it seems like the drive for a competitive advantage
>> caused deployment of a packet ordering workaround in the wrong network
>> location(s), out of a pure misalignment of incentives.
>>
>> RACK rates to fix that in the end, but a lot of damage is already done,
>> and the L4S approach gives switches a flag that can double as proof that
>> RACK is there on the receiver, so they can stop trying to order those
>> packets.
>>
>> So point granted, I understand and agree there's a cost to abandoning
>> that advantage.
>> </aside>
>>
>> But as you also said so well in another thread, this is important.  ("The
>> last unicorn", IIRC.)  How much does it matter if there's a feature that
>> has value today, but only until RACK is widely deployed?  If you were
>> convinced RACK would roll out everywhere within 3 years and SCE would
>> produce better results than L4S over the following 15 years, would that
>> change your mind?
>>
>> It would for me, and that's why I'd like to see SCE explored before
>> making a call.  I think at its core, it provides the same thing L4S does
>> (a high-fidelity explicit congestion signal for the sender), but with
>> much cleaner semantics that can be incrementally added to congestion
>> controls that people are already using.
>>
>> Granted, it still remains to be seen whether SCE in practice can match
>> the results of L4S, and L4S was here first.  But it seems to me L4S comes
>> with some problems that have not yet been examined, and that are nicely
>> dodged by a SCE-based approach.
>>
>> If L4S really is as good as they seem to think, I could imagine getting
>> behind it, but I don't think that's proven yet.  I'm not certain, but
>> all the comparative analyses I remember seeing have been from more or
>> less the same team, and I'm not convinced they don't have some
>> misaligned incentives of their own.
>>
>> I understand a lot of work has gone into L4S, but this move to jump it
>> from interesting experiment to de-facto standard without a more critical
>> review that digs deeper into some of the potential deployment problems
>> has me concerned.
>>
>> If it really does turn out to be good enough to be permanent, I'm not
>> opposed to it, but I'm just not convinced that it's non-harmful, and my
>> default position is that the cleaner solution is going to be better in
>> the long run, if they can do the same job.
>>
>> It's not that I want it to be a fight, but I do want to end up with the
>> best solution we can get.  We only have the one internet.
>>
>> Just my 2c.
>>
>> -Jake
>>
>>
>> _______________________________________________
>> Ecn-sane mailing list
>> Ecn-sane@lists.bufferbloat.net
>> https://lists.bufferbloat.net/listinfo/ecn-sane
>
>
>
> --
> New postal address:
> Google
> 1875 Explorer Street, 10th Floor
> Reston, VA 20190
> _______________________________________________
> Ecn-sane mailing list
> Ecn-sane@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/ecn-sane



-- 

Dave Täht
CTO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-831-205-9740

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Holland, Jake]

[-- Attachment #1: Type: text/plain, Size: 7282 bytes --]

Yeah, great question.

I don't want to answer for the L4S guys, I don't have a good feel for
what they might think.  But it does concern me that there seems to be at
least one tuning parameter that was picked for Reno, which I think I
mentioned on the tsvwg list:
https://tools.ietf.org/html/draft-ietf-tsvwg-aqm-dualq-coupled-08#section-2.1

For SCE, I would assume they'll want to make use of it at some point,
and so they'll have to write a draft for how BBR will handle it.

I think there's an open question of what exactly the rate of SCE
markings would look like for a SCE-capable AQM, and presumably this also
needs to be nailed down before it can be useful.  My initial instinct is
a probabilistic SCE setting based on current queue length, either when
forwarded or when enqueued, but I think this will take some more
thought, and I'm not sure that's best.

But whatever the most informative schedule we can figure out is, if that
info can get back to sender, it can essentially do whatever it thinks is
right, according to the cc it’s running, is my understanding.

-Jake


From: Vint Cerf <vint@google.com>
Date: 2019-03-16 at 14:57
To: "Holland, Jake" <jholland@akamai.com>
Cc: Mikael Abrahamsson <swmike@swm.pp.se>, "David P. Reed" <dpreed@deepplum.com>, "ecn-sane@lists.bufferbloat.net" <ecn-sane@lists.bufferbloat.net>, bloat <bloat@lists.bufferbloat.net>
Subject: Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

where does BBR fit into all this?

v


On Sat, Mar 16, 2019 at 5:39 PM Holland, Jake <jholland@akamai.com<mailto:jholland@akamai.com>> wrote:
On 2019-03-15, 11:37, "Mikael Abrahamsson" <swmike@swm.pp.se<mailto:swmike@swm.pp.se>> wrote:
    L4S has a much better possibility of actually getting deployment into the
    wider Internet packet-moving equipment than anything being talked about
    here. Same with PIE as opposed to FQ_CODEL. I know it's might not be as
    good, but it fits better into actual silicon and it's being proposed by
    people who actually have better channels into the people setting hard
    requirements.

    I suggest you consider joining them instead of opposing them.


Hi Mikael,

I agree it makes sense that fq_anything has issues when you're talking
about the OLT/CMTS/BNG/etc., and I believe it when you tell me PIE
makes better sense there.

But fq_x makes great sense and provides real value for the uplink in a
home, small office, coffee shop, etc. (if you run the final rate limit
on the home side of the access link.)  I'm thinking maybe there's a
disconnect here driven by the different use cases for where AQMs can go.

The thing is, each of these is the most likely congestion point at
different times, and it's worthwhile for each of them to be able to
AQM (and mark packets) under congestion.

One of the several things that bothers me with L4S is that I've seen
precious little concern over interfering with the ability for another
different AQM in-path to mark packets, and because it changes the
semantics of CE, you can't have both working at the same time unless
they both do L4S.

SCE needs a lot of details filled in, but it's so much cleaner that it
seems to me there's reasonably obvious answers to all (or almost all) of
those detail questions, and because the semantics are so much cleaner,
it's much easier to tell it's non-harmful.

<aside regarding="non-harmful">
The point you raised in another thread about reordering is mostly
well-taken, and a good counterpoint to the claim "non-harmful relative
to L4S".

To me it seems sad and dumb that switches ended up trying to make
ordering guarantees at cost of switching performance, because if it's
useful to put ordering in the switch, then it must be equally useful to
put it in the receiver's NIC or OS.

So why isn't it in all the receivers' NIC or OS (where it would render
the switch's ordering efforts moot) instead of in all the switches?

I'm guessing the answer is a competition trap for the switch vendors,
plus "with ordering goes faster than without, when you benchmark the
switch with typical load and current (non-RACK) receivers".

If that's the case, it seems like the drive for a competitive advantage
caused deployment of a packet ordering workaround in the wrong network
location(s), out of a pure misalignment of incentives.

RACK rates to fix that in the end, but a lot of damage is already done,
and the L4S approach gives switches a flag that can double as proof that
RACK is there on the receiver, so they can stop trying to order those
packets.

So point granted, I understand and agree there's a cost to abandoning
that advantage.
</aside>

But as you also said so well in another thread, this is important.  ("The
last unicorn", IIRC.)  How much does it matter if there's a feature that
has value today, but only until RACK is widely deployed?  If you were
convinced RACK would roll out everywhere within 3 years and SCE would
produce better results than L4S over the following 15 years, would that
change your mind?

It would for me, and that's why I'd like to see SCE explored before
making a call.  I think at its core, it provides the same thing L4S does
(a high-fidelity explicit congestion signal for the sender), but with
much cleaner semantics that can be incrementally added to congestion
controls that people are already using.

Granted, it still remains to be seen whether SCE in practice can match
the results of L4S, and L4S was here first.  But it seems to me L4S comes
with some problems that have not yet been examined, and that are nicely
dodged by a SCE-based approach.

If L4S really is as good as they seem to think, I could imagine getting
behind it, but I don't think that's proven yet.  I'm not certain, but
all the comparative analyses I remember seeing have been from more or
less the same team, and I'm not convinced they don't have some
misaligned incentives of their own.

I understand a lot of work has gone into L4S, but this move to jump it
from interesting experiment to de-facto standard without a more critical
review that digs deeper into some of the potential deployment problems
has me concerned.

If it really does turn out to be good enough to be permanent, I'm not
opposed to it, but I'm just not convinced that it's non-harmful, and my
default position is that the cleaner solution is going to be better in
the long run, if they can do the same job.

It's not that I want it to be a fight, but I do want to end up with the
best solution we can get.  We only have the one internet.

Just my 2c.

-Jake


_______________________________________________
Ecn-sane mailing list
Ecn-sane@lists.bufferbloat.net<mailto:Ecn-sane@lists.bufferbloat.net>
https://lists.bufferbloat.net/listinfo/ecn-sane<https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.bufferbloat.net_listinfo_ecn-2Dsane&d=DwMFaQ&c=96ZbZZcaMF4w0F4jpN6LZg&r=bqnFROivDo_4iF8Z3R4DyNWKbbMeXr0LOgLnElT1Ook&m=Z6SbAUystZUjAZ76eHgzuX1g5MhoKi4Ich8EPHag2YY&s=wSu1I5Whay2ozL9k8eMyqhqN-SQVdMnbPzCRx6tyEZ8&e=>


--
New postal address:
Google
1875 Explorer Street, 10th Floor
Reston, VA 20190

[-- Attachment #2: Type: text/html, Size: 12695 bytes --]

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[David P. Reed]

[-- Attachment #1: Type: text/plain, Size: 6616 bytes --]


Vint -
 
BBR is the end-to-end control logic that adjusts the source rate to match the share of the bolttleneck link it should use.
 
It depends on getting reliable current congestion information via packet drops and/or ECN.
 
So the proposal by these guys (not the cable guys) is an attempt to improve the quality of the congestion signal inserted by the router with the bottleneck outbound link.
 
THe cable guys are trying to get a "private" field in the IP header for their own use.
 
 
-----Original Message-----
From: "Vint Cerf" <vint@google.com>
Sent: Saturday, March 16, 2019 5:57pm
To: "Holland, Jake" <jholland@akamai.com>
Cc: "Mikael Abrahamsson" <swmike@swm.pp.se>, "David P. Reed" <dpreed@deepplum.com>, "ecn-sane@lists.bufferbloat.net" <ecn-sane@lists.bufferbloat.net>, "bloat" <bloat@lists.bufferbloat.net>
Subject: Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104



where does BBR fit into all this?
v


On Sat, Mar 16, 2019 at 5:39 PM Holland, Jake <[ jholland@akamai.com ]( mailto:jholland@akamai.com )> wrote:On 2019-03-15, 11:37, "Mikael Abrahamsson" <[ swmike@swm.pp.se ]( mailto:swmike@swm.pp.se )> wrote:
     L4S has a much better possibility of actually getting deployment into the 
     wider Internet packet-moving equipment than anything being talked about 
     here. Same with PIE as opposed to FQ_CODEL. I know it's might not be as 
     good, but it fits better into actual silicon and it's being proposed by 
     people who actually have better channels into the people setting hard 
     requirements.

     I suggest you consider joining them instead of opposing them.


 Hi Mikael,

 I agree it makes sense that fq_anything has issues when you're talking
 about the OLT/CMTS/BNG/etc., and I believe it when you tell me PIE
 makes better sense there.

 But fq_x makes great sense and provides real value for the uplink in a
 home, small office, coffee shop, etc. (if you run the final rate limit
 on the home side of the access link.)  I'm thinking maybe there's a
 disconnect here driven by the different use cases for where AQMs can go.

 The thing is, each of these is the most likely congestion point at
 different times, and it's worthwhile for each of them to be able to
 AQM (and mark packets) under congestion.

 One of the several things that bothers me with L4S is that I've seen
 precious little concern over interfering with the ability for another
 different AQM in-path to mark packets, and because it changes the
 semantics of CE, you can't have both working at the same time unless
 they both do L4S.

 SCE needs a lot of details filled in, but it's so much cleaner that it
 seems to me there's reasonably obvious answers to all (or almost all) of
 those detail questions, and because the semantics are so much cleaner,
 it's much easier to tell it's non-harmful.

 <aside regarding="non-harmful">
 The point you raised in another thread about reordering is mostly
 well-taken, and a good counterpoint to the claim "non-harmful relative
 to L4S".

 To me it seems sad and dumb that switches ended up trying to make
 ordering guarantees at cost of switching performance, because if it's
 useful to put ordering in the switch, then it must be equally useful to
 put it in the receiver's NIC or OS.

 So why isn't it in all the receivers' NIC or OS (where it would render
 the switch's ordering efforts moot) instead of in all the switches?

 I'm guessing the answer is a competition trap for the switch vendors,
 plus "with ordering goes faster than without, when you benchmark the
 switch with typical load and current (non-RACK) receivers".

 If that's the case, it seems like the drive for a competitive advantage
 caused deployment of a packet ordering workaround in the wrong network
 location(s), out of a pure misalignment of incentives.

 RACK rates to fix that in the end, but a lot of damage is already done,
 and the L4S approach gives switches a flag that can double as proof that
 RACK is there on the receiver, so they can stop trying to order those
 packets.

 So point granted, I understand and agree there's a cost to abandoning
 that advantage.
 </aside>

 But as you also said so well in another thread, this is important.  ("The
 last unicorn", IIRC.)  How much does it matter if there's a feature that
 has value today, but only until RACK is widely deployed?  If you were
 convinced RACK would roll out everywhere within 3 years and SCE would
 produce better results than L4S over the following 15 years, would that
 change your mind?

 It would for me, and that's why I'd like to see SCE explored before
 making a call.  I think at its core, it provides the same thing L4S does
 (a high-fidelity explicit congestion signal for the sender), but with
 much cleaner semantics that can be incrementally added to congestion
 controls that people are already using.

 Granted, it still remains to be seen whether SCE in practice can match
 the results of L4S, and L4S was here first.  But it seems to me L4S comes
 with some problems that have not yet been examined, and that are nicely
 dodged by a SCE-based approach.

 If L4S really is as good as they seem to think, I could imagine getting
 behind it, but I don't think that's proven yet.  I'm not certain, but
 all the comparative analyses I remember seeing have been from more or
 less the same team, and I'm not convinced they don't have some
 misaligned incentives of their own.

 I understand a lot of work has gone into L4S, but this move to jump it
 from interesting experiment to de-facto standard without a more critical
 review that digs deeper into some of the potential deployment problems
 has me concerned.

 If it really does turn out to be good enough to be permanent, I'm not
 opposed to it, but I'm just not convinced that it's non-harmful, and my
 default position is that the cleaner solution is going to be better in
 the long run, if they can do the same job.

 It's not that I want it to be a fight, but I do want to end up with the
 best solution we can get.  We only have the one internet.

 Just my 2c.  

 -Jake


 _______________________________________________
 Ecn-sane mailing list
[ Ecn-sane@lists.bufferbloat.net ]( mailto:Ecn-sane@lists.bufferbloat.net )
[ https://lists.bufferbloat.net/listinfo/ecn-sane ]( https://lists.bufferbloat.net/listinfo/ecn-sane )
-- 


New postal address:
Google

1875 Explorer Street, 10th Floor
Reston, VA 20190

[-- Attachment #2: Type: text/html, Size: 9003 bytes --]

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Vint Cerf]

[-- Attachment #1: Type: text/plain, Size: 6844 bytes --]

thanks, David - that's the information I was looking for.

v


On Sun, Mar 17, 2019 at 2:07 PM David P. Reed <dpreed@deepplum.com> wrote:

> Vint -
>
>
>
> BBR is the end-to-end control logic that adjusts the source rate to match
> the share of the bolttleneck link it should use.
>
>
>
> It depends on getting reliable current congestion information via packet
> drops and/or ECN.
>
>
>
> So the proposal by these guys (not the cable guys) is an attempt to
> improve the quality of the congestion signal inserted by the router with
> the bottleneck outbound link.
>
>
>
> THe cable guys are trying to get a "private" field in the IP header for
> their own use.
>
>
>
>
>
> -----Original Message-----
> From: "Vint Cerf" <vint@google.com>
> Sent: Saturday, March 16, 2019 5:57pm
> To: "Holland, Jake" <jholland@akamai.com>
> Cc: "Mikael Abrahamsson" <swmike@swm.pp.se>, "David P. Reed" <
> dpreed@deepplum.com>, "ecn-sane@lists.bufferbloat.net" <
> ecn-sane@lists.bufferbloat.net>, "bloat" <bloat@lists.bufferbloat.net>
> Subject: Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation
> and experimentation of TCP Prague/L4S hackaton at IETF104
>
> where does BBR fit into all this?
> v
>
> On Sat, Mar 16, 2019 at 5:39 PM Holland, Jake <jholland@akamai.com> wrote:
>
>> On 2019-03-15, 11:37, "Mikael Abrahamsson" <swmike@swm.pp.se> wrote:
>>     L4S has a much better possibility of actually getting deployment into
>> the
>>     wider Internet packet-moving equipment than anything being talked
>> about
>>     here. Same with PIE as opposed to FQ_CODEL. I know it's might not be
>> as
>>     good, but it fits better into actual silicon and it's being proposed
>> by
>>     people who actually have better channels into the people setting hard
>>     requirements.
>>
>>     I suggest you consider joining them instead of opposing them.
>>
>>
>> Hi Mikael,
>>
>> I agree it makes sense that fq_anything has issues when you're talking
>> about the OLT/CMTS/BNG/etc., and I believe it when you tell me PIE
>> makes better sense there.
>>
>> But fq_x makes great sense and provides real value for the uplink in a
>> home, small office, coffee shop, etc. (if you run the final rate limit
>> on the home side of the access link.)  I'm thinking maybe there's a
>> disconnect here driven by the different use cases for where AQMs can go.
>>
>> The thing is, each of these is the most likely congestion point at
>> different times, and it's worthwhile for each of them to be able to
>> AQM (and mark packets) under congestion.
>>
>> One of the several things that bothers me with L4S is that I've seen
>> precious little concern over interfering with the ability for another
>> different AQM in-path to mark packets, and because it changes the
>> semantics of CE, you can't have both working at the same time unless
>> they both do L4S.
>>
>> SCE needs a lot of details filled in, but it's so much cleaner that it
>> seems to me there's reasonably obvious answers to all (or almost all) of
>> those detail questions, and because the semantics are so much cleaner,
>> it's much easier to tell it's non-harmful.
>>
>> <aside regarding="non-harmful">
>> The point you raised in another thread about reordering is mostly
>> well-taken, and a good counterpoint to the claim "non-harmful relative
>> to L4S".
>>
>> To me it seems sad and dumb that switches ended up trying to make
>> ordering guarantees at cost of switching performance, because if it's
>> useful to put ordering in the switch, then it must be equally useful to
>> put it in the receiver's NIC or OS.
>>
>> So why isn't it in all the receivers' NIC or OS (where it would render
>> the switch's ordering efforts moot) instead of in all the switches?
>>
>> I'm guessing the answer is a competition trap for the switch vendors,
>> plus "with ordering goes faster than without, when you benchmark the
>> switch with typical load and current (non-RACK) receivers".
>>
>> If that's the case, it seems like the drive for a competitive advantage
>> caused deployment of a packet ordering workaround in the wrong network
>> location(s), out of a pure misalignment of incentives.
>>
>> RACK rates to fix that in the end, but a lot of damage is already done,
>> and the L4S approach gives switches a flag that can double as proof that
>> RACK is there on the receiver, so they can stop trying to order those
>> packets.
>>
>> So point granted, I understand and agree there's a cost to abandoning
>> that advantage.
>> </aside>
>>
>> But as you also said so well in another thread, this is important.  ("The
>> last unicorn", IIRC.)  How much does it matter if there's a feature that
>> has value today, but only until RACK is widely deployed?  If you were
>> convinced RACK would roll out everywhere within 3 years and SCE would
>> produce better results than L4S over the following 15 years, would that
>> change your mind?
>>
>> It would for me, and that's why I'd like to see SCE explored before
>> making a call.  I think at its core, it provides the same thing L4S does
>> (a high-fidelity explicit congestion signal for the sender), but with
>> much cleaner semantics that can be incrementally added to congestion
>> controls that people are already using.
>>
>> Granted, it still remains to be seen whether SCE in practice can match
>> the results of L4S, and L4S was here first.  But it seems to me L4S comes
>> with some problems that have not yet been examined, and that are nicely
>> dodged by a SCE-based approach.
>>
>> If L4S really is as good as they seem to think, I could imagine getting
>> behind it, but I don't think that's proven yet.  I'm not certain, but
>> all the comparative analyses I remember seeing have been from more or
>> less the same team, and I'm not convinced they don't have some
>> misaligned incentives of their own.
>>
>> I understand a lot of work has gone into L4S, but this move to jump it
>> from interesting experiment to de-facto standard without a more critical
>> review that digs deeper into some of the potential deployment problems
>> has me concerned.
>>
>> If it really does turn out to be good enough to be permanent, I'm not
>> opposed to it, but I'm just not convinced that it's non-harmful, and my
>> default position is that the cleaner solution is going to be better in
>> the long run, if they can do the same job.
>>
>> It's not that I want it to be a fight, but I do want to end up with the
>> best solution we can get.  We only have the one internet.
>>
>> Just my 2c.
>>
>> -Jake
>>
>>
>> _______________________________________________
>> Ecn-sane mailing list
>> Ecn-sane@lists.bufferbloat.net
>> https://lists.bufferbloat.net/listinfo/ecn-sane
>
>
> --
> New postal address:
> Google
> 1875 Explorer Street, 10th Floor
> Reston, VA 20190
>


-- 
New postal address:
Google
1875 Explorer Street, 10th Floor
Reston, VA 20190

[-- Attachment #2: Type: text/html, Size: 9736 bytes --]

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Greg White]

[-- Attachment #1: Type: text/plain, Size: 10232 bytes --]

That is ridiculous.

You clearly haven’t read the drafts, and so are speaking from a position of ignorance.  Please get informed before making statements like this.

There is *absolutely* nothing cable-specific or “private” about L4S.  It is being developed in an open forum, the IETF!!   Yes, the cable industry is adopting L4S – because we recognized its potential.  Others are too, and anyone can.  It is a totally open spec, and has been since the initial drafts came out of the RITE project.  The cable industry was not involved in RITE (in fact the technology was first demonstrated on DSL equipment), and we learned about L4S when the rest of the world did.  We decided to become early adopters.  Yes, we were quiet about the fact that we were planning on adopting it (until now).

If individuals drop out of participating in the IETF, they shouldn’t be upset if the IETF continues to make progress on developing Internet technology in their absence.  It seems pretty disingenuous for DT to form his own private working group to come up with an incompatible, and limited, alternative to the ongoing work in IETF, then spring it on the IETF and start this FUD war.

The craziest thing about this whole thread is that there is a heck of a lot in common between L4S and SCE.  More in common than different.  My initial belief was that we all had similar goals (eliminating buffering latency in the internet) and we’d be able to achieve a meeting of the minds on the best way to use ECT(1) to achieve it.  Now, I’m not so sure what DT’s motivation is.

If I can boil this down for the people who are jumping into this without reading the drafts:


  *   Both L4S and SCE are attempting to provide congestion-controlled senders with better congestion signals so that flows can achieve link capacity without buffering delay.
  *   Both are proposing to use ECT(1) as part of the mechanism, but to use it in different ways.
  *   SCE’s usage of ECT(1) potentially allows an automatic fallback to traditional Cubic behavior if the bottleneck link is a single-queue classic-ECN AQM (do any of these exist?), whereas L4S will need to detect such a condition via RTT measurement
  *   L4S’s usage of ECT(1) allows links to identify new senders and take advantage of new sender features like reordering tolerance that can further drive down latency in many common link technologies.
  *   SCE will only work if the bottleneck link implements fq.  Some bottleneck network gear will not be able to implement fq or will not implement it due to its undesirable side effects (see section 6 of RFC 8290).
  *   L4S will work if the bottleneck link implements *either* fq or dual queue.

Beyond that, they are *very,very* similar.

But, L4S has been demonstrated in real equipment and in simulation, and leverages an existing congestion controller that is available in Linux and Windows (with some tweaks).  SCE leverages a paragraph in a draft that describes a first guess about how a congestion controller might work.

L4S has defined a congestion feedback mechanism so that these congestion signals can get back to the sender.  SCE offers that “we’ll propose something later”.

BBR currently does not listen to explicit congestion signals, but it could be updated to do so (for either SCE or L4S).

-Greg


From: Bloat <bloat-bounces@lists.bufferbloat.net> on behalf of "David P. Reed" <dpreed@deepplum.com>
Date: Sunday, March 17, 2019 at 12:07 PM
To: Vint Cerf <vint@google.com>
Cc: bloat <bloat@lists.bufferbloat.net>, "ecn-sane@lists.bufferbloat.net" <ecn-sane@lists.bufferbloat.net>
Subject: Re: [Bloat] [Ecn-sane] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104


Vint -



BBR is the end-to-end control logic that adjusts the source rate to match the share of the bolttleneck link it should use.



It depends on getting reliable current congestion information via packet drops and/or ECN.



So the proposal by these guys (not the cable guys) is an attempt to improve the quality of the congestion signal inserted by the router with the bottleneck outbound link.



THe cable guys are trying to get a "private" field in the IP header for their own use.





-----Original Message-----
From: "Vint Cerf" <vint@google.com>
Sent: Saturday, March 16, 2019 5:57pm
To: "Holland, Jake" <jholland@akamai.com>
Cc: "Mikael Abrahamsson" <swmike@swm.pp.se>, "David P. Reed" <dpreed@deepplum.com>, "ecn-sane@lists.bufferbloat.net" <ecn-sane@lists.bufferbloat.net>, "bloat" <bloat@lists.bufferbloat.net>
Subject: Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104
where does BBR fit into all this?
v

On Sat, Mar 16, 2019 at 5:39 PM Holland, Jake <jholland@akamai.com<mailto:jholland@akamai.com>> wrote:
On 2019-03-15, 11:37, "Mikael Abrahamsson" <swmike@swm.pp.se<mailto:swmike@swm.pp.se>> wrote:
    L4S has a much better possibility of actually getting deployment into the
    wider Internet packet-moving equipment than anything being talked about
    here. Same with PIE as opposed to FQ_CODEL. I know it's might not be as
    good, but it fits better into actual silicon and it's being proposed by
    people who actually have better channels into the people setting hard
    requirements.

    I suggest you consider joining them instead of opposing them.


Hi Mikael,

I agree it makes sense that fq_anything has issues when you're talking
about the OLT/CMTS/BNG/etc., and I believe it when you tell me PIE
makes better sense there.

But fq_x makes great sense and provides real value for the uplink in a
home, small office, coffee shop, etc. (if you run the final rate limit
on the home side of the access link.)  I'm thinking maybe there's a
disconnect here driven by the different use cases for where AQMs can go.

The thing is, each of these is the most likely congestion point at
different times, and it's worthwhile for each of them to be able to
AQM (and mark packets) under congestion.

One of the several things that bothers me with L4S is that I've seen
precious little concern over interfering with the ability for another
different AQM in-path to mark packets, and because it changes the
semantics of CE, you can't have both working at the same time unless
they both do L4S.

SCE needs a lot of details filled in, but it's so much cleaner that it
seems to me there's reasonably obvious answers to all (or almost all) of
those detail questions, and because the semantics are so much cleaner,
it's much easier to tell it's non-harmful.

<aside regarding="non-harmful">
The point you raised in another thread about reordering is mostly
well-taken, and a good counterpoint to the claim "non-harmful relative
to L4S".

To me it seems sad and dumb that switches ended up trying to make
ordering guarantees at cost of switching performance, because if it's
useful to put ordering in the switch, then it must be equally useful to
put it in the receiver's NIC or OS.

So why isn't it in all the receivers' NIC or OS (where it would render
the switch's ordering efforts moot) instead of in all the switches?

I'm guessing the answer is a competition trap for the switch vendors,
plus "with ordering goes faster than without, when you benchmark the
switch with typical load and current (non-RACK) receivers".

If that's the case, it seems like the drive for a competitive advantage
caused deployment of a packet ordering workaround in the wrong network
location(s), out of a pure misalignment of incentives.

RACK rates to fix that in the end, but a lot of damage is already done,
and the L4S approach gives switches a flag that can double as proof that
RACK is there on the receiver, so they can stop trying to order those
packets.

So point granted, I understand and agree there's a cost to abandoning
that advantage.
</aside>

But as you also said so well in another thread, this is important.  ("The
last unicorn", IIRC.)  How much does it matter if there's a feature that
has value today, but only until RACK is widely deployed?  If you were
convinced RACK would roll out everywhere within 3 years and SCE would
produce better results than L4S over the following 15 years, would that
change your mind?

It would for me, and that's why I'd like to see SCE explored before
making a call.  I think at its core, it provides the same thing L4S does
(a high-fidelity explicit congestion signal for the sender), but with
much cleaner semantics that can be incrementally added to congestion
controls that people are already using.

Granted, it still remains to be seen whether SCE in practice can match
the results of L4S, and L4S was here first.  But it seems to me L4S comes
with some problems that have not yet been examined, and that are nicely
dodged by a SCE-based approach.

If L4S really is as good as they seem to think, I could imagine getting
behind it, but I don't think that's proven yet.  I'm not certain, but
all the comparative analyses I remember seeing have been from more or
less the same team, and I'm not convinced they don't have some
misaligned incentives of their own.

I understand a lot of work has gone into L4S, but this move to jump it
from interesting experiment to de-facto standard without a more critical
review that digs deeper into some of the potential deployment problems
has me concerned.

If it really does turn out to be good enough to be permanent, I'm not
opposed to it, but I'm just not convinced that it's non-harmful, and my
default position is that the cleaner solution is going to be better in
the long run, if they can do the same job.

It's not that I want it to be a fight, but I do want to end up with the
best solution we can get.  We only have the one internet.

Just my 2c.

-Jake


_______________________________________________
Ecn-sane mailing list
Ecn-sane@lists.bufferbloat.net<mailto:Ecn-sane@lists.bufferbloat.net>
https://lists.bufferbloat.net/listinfo/ecn-sane

--
New postal address:
Google
1875 Explorer Street, 10th Floor
Reston, VA 20190

[-- Attachment #2: Type: text/html, Size: 21730 bytes --]

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Jonathan Morton]

> 	• SCE will only work if the bottleneck link implements fq.  Some bottleneck network gear will not be able to implement fq or will not implement it due to its undesirable side effects (see section 6 of RFC 8290).

> SCE leverages a paragraph in a draft that describes a first guess about how a congestion controller might work.

We have an update in the works that should enable RTT-fair convergence with single-queue AQMs, whether they support SCE or not.  To do this using the simplest reasonable adjustments to existing congestion control algorithms, the setpoint is no longer fixed at 50% but varies with the cwnd of each flow.  And yes, we have worked out what those adjustments should look like in practice, but we haven't yet had time to run tests, or describe them in a nicely formatted I-D.

This update should also allow a very DCTCP-like congestion control algorithm to work correctly with SCE, as long as it acts conventionally with CE marks and only has the reduced response to SCE marks.  That's something that DCTCP itself currently does not do.

> 	• SCE’s usage of ECT(1) potentially allows an automatic fallback to traditional Cubic behavior if the bottleneck link is a single-queue classic-ECN AQM (do any of these exist?), whereas L4S will need to detect such a condition via RTT measurement

From my standpoint, the major objection to L4S is that it is not incrementally deployable, because DCTCP starves conventional TCPs unless run through an isolated queue.  This is something we quickly realised when L4S was first announced.  It is simply not practical to require all middleboxes on the path to support L4S before L4S endpoints can safely be deployed, except in the isolated and very controlled environments where DCTCP was "proved".

> I find it extremely disappointing that some people on this list are taking such a negative attitude to the major development in their own field that they seem not to have noticed since it first hit the limelight in 2015.

It is not at all true that we were unaware of L4S.  Rather, we quite reasonably believed it would never get traction in the IETF or in the Internet at large unless that problem was robustly solved - and we thought the obvious solution *was* to use ECT(1) as SCE does, and to fix Diffserv (so that it becomes e2e usable to some degree) or implement FQ if isolating low-latency-assured traffic is so important.

Incidentally, during that time we were implementing a good FQ system that is now in Linux and in commercial products. Granted, it isn't designed for the sort of high-capacity links where FQ is traditionally considered impractical.

> L4S has defined a congestion feedback mechanism so that these congestion signals can get back to the sender.  SCE offers that “we’ll propose something later”.

It should be straightforward to adjust AccECN so that it primarily carries SCE information instead of unnecessarily detailed CE information.  That's one obvious solution, which we hoped those already familiar with L4S would recognise without explicit prompting.

We have outlines of other feedback methods, still awaiting conversion to the proper document format, including one that doesn't require a new TCP option (I understand there are objections to such things, centred around paranoid firewalls) and which existing middleboxes and endpoints will transparently ignore (like the rest of SCE).  It uses the NS bit which was also freed up by the obsoleting of Nonce Sum.

The I-D presently available defines the SCE codepoint and very little else.  This is due to separation of concerns.  Other I-Ds will define feedback mechanisms, detailed modifications to congestion control algorithms, and recommendations as to what AQMs should do.

Perhaps if we get a chance to work, instead of responding to manufactured outrage that we dare to propose something different, these extra documents might surface in time for discussion.

 - Jonathan Morton

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Greg White]

On 3/18/19, 11:35 PM, "Jonathan Morton" <chromatix99@gmail.com> wrote:

    From my standpoint, the major objection to L4S is that it is not incrementally deployable, because DCTCP starves conventional TCPs unless run through an isolated queue.  This is something we quickly realised when L4S was first announced.  It is simply not practical to require all middleboxes on the path to support L4S before L4S endpoints can safely be deployed, except in the isolated and very controlled environments where DCTCP was "proved".
    
[GW] But this isn't true!    L4S utilizes TCP Prague, which falls back to traditional congestion control if the bottleneck link doesn't provide isolation.  

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Jonathan Morton]

> On 19 Mar, 2019, at 7:52 am, Greg White <g.white@CableLabs.com> wrote:
> 
> L4S utilizes TCP Prague, which falls back to traditional congestion control if the bottleneck link doesn't provide isolation.  

You see, this is the part I find difficult to believe that it will operate reliably.  For a start, I have seen no detailed public description of TCP Prague, even though it has supposedly been in "open" development for so long.  My most recent information is that it's essentially a slightly modified DCTCP.

"  It would take time for endpoints to distinguish classic and L4S ECN
   marking.  An increase in queuing delay or in delay variation would be
   a tell-tale sign, but it is not yet clear where a line would be drawn
   between the two behaviours.  "

Internet history is littered with failed attempts at implementing delay-sensitive TCPs.  I can immediately think of several reasons why delay can and will vary for reasons other than the bottleneck not implementing an isolated queue  (just ask the BBR devs).  The mere presence of a wifi link on the path, even if it is never the bottleneck, would be a trivial and common example.

So please explain (or point to good documentation) how TCP Prague robustly avoids misbehaving in a standard ECN environment, as is presently deployed.


SCE explicitly does not rely on specific changes in behaviour by endpoints.  It just provides a conduit of information from the network to the receiver, in addition to standard ECN behaviour.  The receiver is free to ignore that information, without harming the network, and will naturally behave normally and safely when that information is absent.  We have a proof-of-concept implementation (a trivial mod of sch_codel and sch_fq_codel) which successfully passes this information across the Internet and works with (is transparently ignored by) existing endpoints and middleboxes.

In short, SCE is incrementally deployable by design.

The broader system of feedback and modified congestion control, which I call ELR (Explicit Load Regulation) as an umbrella term, offers benefits which, yes, have not yet been proved - but which are straightforward in concept and should be amenable to analysis.  It seems likely that some work from L4S can be used in this context.

 - Jonathan Morton

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Sebastian Moeller]

> On Mar 19, 2019, at 08:10, Jonathan Morton <chromatix99@gmail.com> wrote:
> 
>> On 19 Mar, 2019, at 7:52 am, Greg White <g.white@CableLabs.com> wrote:
>> 
>> L4S utilizes TCP Prague, which falls back to traditional congestion control if the bottleneck link doesn't provide isolation.  
> 
> You see, this is the part I find difficult to believe that it will operate reliably.  For a start, I have seen no detailed public description of TCP Prague, even though it has supposedly been in "open" development for so long.  My most recent information is that it's essentially a slightly modified DCTCP.
> 
> "  It would take time for endpoints to distinguish classic and L4S ECN
>   marking.  An increase in queuing delay or in delay variation would be
>   a tell-tale sign, but it is not yet clear where a line would be drawn
>   between the two behaviours.  "

	IMHO this is caused by the fact that ECT(1) is simply not suitable as a classifier, as it will only reliably classify unmarked packets, anything marked CE will looses the destinction whether the flow considers itself L4S ready or not. Could anyone point me to the section in the L4S RFCs that discusses this, please?

https://datatracker.ietf.org/doc/draft-ietf-tsvwg-ecn-l4s-id/ has the following:
" Given shortage of codepoints, both L4S and classic ECN sides of
         an AQM would have to use the same CE codepoint to indicate that
         a packet had experienced congestion.  If a packet that had
         already been marked CE in an upstream buffer arrived at a
         subsequent AQM, this AQM would then have to guess whether to
         classify CE packets as L4S or classic ECN.  Choosing the L4S
         treatment would be a safer choice, because then a few classic
         packets might arrive early, rather than a few L4S packets
         arriving late;"

But how is the L4S queue actually maintaining its low latency if it just admitted an non-L4S flow? This _might_ work if CE marked packets are rare, but IMHO this confirms my assessment that ECT(1) is a terrible choice for a classifier bit.

Best Regards
	Sebastian




> Internet history is littered with failed attempts at implementing delay-sensitive TCPs.  I can immediately think of several reasons why delay can and will vary for reasons other than the bottleneck not implementing an isolated queue  (just ask the BBR devs).  The mere presence of a wifi link on the path, even if it is never the bottleneck, would be a trivial and common example.
> 
> So please explain (or point to good documentation) how TCP Prague robustly avoids misbehaving in a standard ECN environment, as is presently deployed.
> 
> 
> SCE explicitly does not rely on specific changes in behaviour by endpoints.  It just provides a conduit of information from the network to the receiver, in addition to standard ECN behaviour.  The receiver is free to ignore that information, without harming the network, and will naturally behave normally and safely when that information is absent.  We have a proof-of-concept implementation (a trivial mod of sch_codel and sch_fq_codel) which successfully passes this information across the Internet and works with (is transparently ignored by) existing endpoints and middleboxes.
> 
> In short, SCE is incrementally deployable by design.
> 
> The broader system of feedback and modified congestion control, which I call ELR (Explicit Load Regulation) as an umbrella term, offers benefits which, yes, have not yet been proved - but which are straightforward in concept and should be amenable to analysis.  It seems likely that some work from L4S can be used in this context.
> 
> - Jonathan Morton
> 
> _______________________________________________
> Bloat mailing list
> Bloat@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/bloat

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Sebastian Moeller]

> On Mar 19, 2019, at 05:44, Greg White <g.white@CableLabs.com> wrote:
> If I can boil this down for the people who are jumping into this without reading the drafts:
>  
> 	• Both L4S and SCE are attempting to provide congestion-controlled senders with better congestion signals so that flows can achieve link capacity without buffering delay. 
> 	• Both are proposing to use ECT(1) as part of the mechanism, but to use it in different ways.

	SCE tries to encode information about the quantitative congestion state of the marking AQM into ECT(1), while L4S tries to use this as a general identifier of promised behavior as a receiver of CE marks, or rather as an indication that flows marked ECT(1) will not respond to CE marks as described in rfc3168. Which realistically means any non-L4S AQM needs to learn quickly to drop ECT(1) packets instead of marking them CE; that seems better controlled than waiting for a fall-back to rfc3168-compliant CE response due to a heuristic based on RTT variation.

> 	• SCE’s usage of ECT(1) potentially allows an automatic fallback to traditional Cubic behavior if the bottleneck link is a single-queue classic-ECN AQM (do any of these exist?), whereas L4S will need to detect such a condition via RTT measurement
> 	• L4S’s usage of ECT(1) allows links to identify new senders and take advantage of new sender features like reordering tolerance that can further drive down latency in many common link technologies.

	But L4S is incapable of _reliably_ classifying L4S flows/packets as CE-marked packets default to L4S-treatment. This indicates to me, that ECT(1) is not really suited as a reliable L4S identifier, what am I missing? 
This ambiguity leads to the question of the side-effects of this leaky classification: what about re-ordering of CE-marked packets? I hope that out of caution CE-marked packets will not be re-ordered as these are very much not guaranteed to employ RACK. (And tangentially, how is a link that desires more latitude for re-ordering going to deal with the RACK requirement to keep the re-ordering windows <= 1 RTT, given that RTTs over the internet differ from a few to dozens of ms. . Is there any study showing how RACK and re-ordering actually interact in real-life?) And how is it going to help a link in regards to re-ordering at all? It has been argued, that links do not differentiate flows at all, and assuming TCP traffic to coexist for a long time with (DC)TCP_Prague traffic, how can a link actually allow more re-ordering than currently tolerable without severely impacting the TCP flows? If it just transmits all ECT(1) packets in its queue things will be a bit better than now, but after the egress queue is emptied the link might still be stalled until the re-transmit of ECT(0) and CE marked packets is finished, no?


> 	• SCE will only work if the bottleneck link implements fq.  Some bottleneck network gear will not be able to implement fq or will not implement it due to its undesirable side effects (see section 6 of RFC 8290).
> 	• L4S will work if the bottleneck link implements *either* fq or dual queue.

	The proof ought to e in the pudding ;) is there data showing an working L4S fq-AQM?

>  
> Beyond that, they are *very,very* similar.  
>  
> But, L4S has been demonstrated in real equipment and in simulation, and leverages an existing congestion controller that is available in Linux and Windows (with some tweaks).  

	As far as I can see the public git repository for TCP Prague is only a few days old so how could that be "available in Linux and Windows" right now, and one could similarly argue that it will only take a few tweaks to teach cubic how to deal with SCE.


So I have no pony in this race as I am outside of the field, but the L4S RFCs seem to promise more than they 



> SCE leverages a paragraph in a draft that describes a first guess about how a congestion controller might work.
>  
> L4S has defined a congestion feedback mechanism so that these congestion signals can get back to the sender.  SCE offers that “we’ll propose something later”.
>  
> BBR currently does not listen to explicit congestion signals, but it could be updated to do so (for either SCE or L4S).
>  
> -Greg
>  
>  
> From: Bloat <bloat-bounces@lists.bufferbloat.net> on behalf of "David P. Reed" <dpreed@deepplum.com>
> Date: Sunday, March 17, 2019 at 12:07 PM
> To: Vint Cerf <vint@google.com>
> Cc: bloat <bloat@lists.bufferbloat.net>, "ecn-sane@lists.bufferbloat.net" <ecn-sane@lists.bufferbloat.net>
> Subject: Re: [Bloat] [Ecn-sane] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104
>  
> Vint -
>  
> BBR is the end-to-end control logic that adjusts the source rate to match the share of the bolttleneck link it should use.
>  
> It depends on getting reliable current congestion information via packet drops and/or ECN.
>  
> So the proposal by these guys (not the cable guys) is an attempt to improve the quality of the congestion signal inserted by the router with the bottleneck outbound link.
>  
> THe cable guys are trying to get a "private" field in the IP header for their own use.
>  
>  
> -----Original Message-----
> From: "Vint Cerf" <vint@google.com>
> Sent: Saturday, March 16, 2019 5:57pm
> To: "Holland, Jake" <jholland@akamai.com>
> Cc: "Mikael Abrahamsson" <swmike@swm.pp.se>, "David P. Reed" <dpreed@deepplum.com>, "ecn-sane@lists.bufferbloat.net" <ecn-sane@lists.bufferbloat.net>, "bloat" <bloat@lists.bufferbloat.net>
> Subject: Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104
> 
> where does BBR fit into all this?
> v
>  
> On Sat, Mar 16, 2019 at 5:39 PM Holland, Jake <jholland@akamai.com> wrote:
>> On 2019-03-15, 11:37, "Mikael Abrahamsson" <swmike@swm.pp.se> wrote:
>>     L4S has a much better possibility of actually getting deployment into the 
>>     wider Internet packet-moving equipment than anything being talked about 
>>     here. Same with PIE as opposed to FQ_CODEL. I know it's might not be as 
>>     good, but it fits better into actual silicon and it's being proposed by 
>>     people who actually have better channels into the people setting hard 
>>     requirements.
>> 
>>     I suggest you consider joining them instead of opposing them.
>> 
>> 
>> Hi Mikael,
>> 
>> I agree it makes sense that fq_anything has issues when you're talking
>> about the OLT/CMTS/BNG/etc., and I believe it when you tell me PIE
>> makes better sense there.
>> 
>> But fq_x makes great sense and provides real value for the uplink in a
>> home, small office, coffee shop, etc. (if you run the final rate limit
>> on the home side of the access link.)  I'm thinking maybe there's a
>> disconnect here driven by the different use cases for where AQMs can go.
>> 
>> The thing is, each of these is the most likely congestion point at
>> different times, and it's worthwhile for each of them to be able to
>> AQM (and mark packets) under congestion.
>> 
>> One of the several things that bothers me with L4S is that I've seen
>> precious little concern over interfering with the ability for another
>> different AQM in-path to mark packets, and because it changes the
>> semantics of CE, you can't have both working at the same time unless
>> they both do L4S.
>> 
>> SCE needs a lot of details filled in, but it's so much cleaner that it
>> seems to me there's reasonably obvious answers to all (or almost all) of
>> those detail questions, and because the semantics are so much cleaner,
>> it's much easier to tell it's non-harmful.
>> 
>> <aside regarding="non-harmful">
>> The point you raised in another thread about reordering is mostly
>> well-taken, and a good counterpoint to the claim "non-harmful relative
>> to L4S".
>> 
>> To me it seems sad and dumb that switches ended up trying to make
>> ordering guarantees at cost of switching performance, because if it's
>> useful to put ordering in the switch, then it must be equally useful to
>> put it in the receiver's NIC or OS.
>> 
>> So why isn't it in all the receivers' NIC or OS (where it would render
>> the switch's ordering efforts moot) instead of in all the switches?
>> 
>> I'm guessing the answer is a competition trap for the switch vendors,
>> plus "with ordering goes faster than without, when you benchmark the
>> switch with typical load and current (non-RACK) receivers".
>> 
>> If that's the case, it seems like the drive for a competitive advantage
>> caused deployment of a packet ordering workaround in the wrong network
>> location(s), out of a pure misalignment of incentives.
>> 
>> RACK rates to fix that in the end, but a lot of damage is already done,
>> and the L4S approach gives switches a flag that can double as proof that
>> RACK is there on the receiver, so they can stop trying to order those
>> packets.
>> 
>> So point granted, I understand and agree there's a cost to abandoning
>> that advantage.
>> </aside>
>> 
>> But as you also said so well in another thread, this is important.  ("The
>> last unicorn", IIRC.)  How much does it matter if there's a feature that
>> has value today, but only until RACK is widely deployed?  If you were
>> convinced RACK would roll out everywhere within 3 years and SCE would
>> produce better results than L4S over the following 15 years, would that
>> change your mind?
>> 
>> It would for me, and that's why I'd like to see SCE explored before
>> making a call.  I think at its core, it provides the same thing L4S does
>> (a high-fidelity explicit congestion signal for the sender), but with
>> much cleaner semantics that can be incrementally added to congestion
>> controls that people are already using.
>> 
>> Granted, it still remains to be seen whether SCE in practice can match
>> the results of L4S, and L4S was here first.  But it seems to me L4S comes
>> with some problems that have not yet been examined, and that are nicely
>> dodged by a SCE-based approach.
>> 
>> If L4S really is as good as they seem to think, I could imagine getting
>> behind it, but I don't think that's proven yet.  I'm not certain, but
>> all the comparative analyses I remember seeing have been from more or
>> less the same team, and I'm not convinced they don't have some
>> misaligned incentives of their own.
>> 
>> I understand a lot of work has gone into L4S, but this move to jump it
>> from interesting experiment to de-facto standard without a more critical
>> review that digs deeper into some of the potential deployment problems
>> has me concerned.
>> 
>> If it really does turn out to be good enough to be permanent, I'm not
>> opposed to it, but I'm just not convinced that it's non-harmful, and my
>> default position is that the cleaner solution is going to be better in
>> the long run, if they can do the same job.
>> 
>> It's not that I want it to be a fight, but I do want to end up with the
>> best solution we can get.  We only have the one internet.
>> 
>> Just my 2c.  
>> 
>> -Jake
>> 
>> 
>> _______________________________________________
>> Ecn-sane mailing list
>> Ecn-sane@lists.bufferbloat.net
>> https://lists.bufferbloat.net/listinfo/ecn-sane
> 
> -- 
> New postal address:
> Google
> 1875 Explorer Street, 10th Floor
> Reston, VA 20190
> _______________________________________________
> Bloat mailing list
> Bloat@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/bloat

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Dave Taht]

On Tue, Mar 19, 2019 at 5:44 AM Greg White <g.white@cablelabs.com> wrote:
>
> That is ridiculous.
>
>
>
> You clearly haven’t read the drafts, and so are speaking from a position of ignorance.  Please get informed before making statements like this.

I've read all the drafts, 3 times, and made pithy comments when they
came out. I've been trying to get other knowlegable people in the
daily grind of modern DC netops to read them also for years. I hope
more, now do.

>
>
> There is *absolutely* nothing cable-specific or “private” about L4S.  It is being developed in an open forum, the IETF!!   Yes, the cable industry is adopting L4S – because we recognized its potential.  Others are too, and anyone can.  It is a totally open spec, and has been since the initial drafts came out of the RITE project.  The cable industry was not involved in RITE (in fact the technology was first demonstrated on DSL equipment), and we learned about L4S when the rest of the world did.  We decided to become early adopters.  Yes, we were quiet about the fact that we were planning on adopting it (until now).
>
>
>
> If individuals drop out of participating in the IETF, they shouldn’t be upset if the IETF continues to make progress on developing Internet technology in their absence.  It seems pretty disingenuous for DT to form his own private working group to come up with an incompatible, and limited, alternative to the ongoing work in IETF, then spring it on the IETF and start this FUD war.

We announced it publicly back in august with our charter and goals on
bloat and aqm mailing lists.

Nobody spoke up then saying l4s was still alive either in the ietf or privately.

We published a charter and outline of scope:
https://www.bufferbloat.net/projects/ecn-sane/wiki/

And we formed into teams:
https://www.bufferbloat.net/projects/ecn-sane/wiki/rules/

And published position papers.

6 months of work on dealing with ecn issues finally has as it's first
result, the SCE draft.

You calling me disingenuous is disingenuous.

>
>
> The craziest thing about this whole thread is that there is a heck of a lot in common between L4S and SCE.

Yep, they do!

Yes, I think we achieved consensus long ago that a single queued AQM
cannot work with an earlier indication of congestion than drop without
changing the endpoints. We also achieved consensus that an earlier
congestion notification was potentially useful in some respects.

Repurposing CE, and using up ECT_1, was all that was on the table before.

>More in common than different.  My initial belief was that we all had similar goals (eliminating buffering latency in the internet) and we’d be able to achieve a meeting of the minds on the best way to use ECT(1) to achieve it.

If I could merely have got the cable industry to reduce the buffering
in their cmts ends from 600+ms to 100ms in the last 8 years, I'd have
been happy.

Two things. 1)  I believe - along with just about everybody I know in
the DC business - few that have bothered to think of ecn at all -
(none have deployed it). In every conversation about l4s is the
presumption that the other person i the conversation already thinks
ecn is a good idea. I know a lot of people that don't think it is. Me,
when it comes to ECN I am firmly on the yellow team - chicken - see
above position paper - in general.

2) Bufferbloat.net deployed solutions starting in 2012 that work for
fixing both inbound and outbound buffering. We shipped sch_cake in
august after 3 years of deployment testing.  I would rather like y'all
to add sch_cake to your test matrix.

> Now, I’m not so sure what DT’s motivation is.

My motivation is always to eliminate bufferbloat and build a better
internet. It's the motto on my patreon page.

>
>
>
> If I can boil this down for the people who are jumping into this without reading the drafts:
>
>
>
> Both L4S and SCE are attempting to provide congestion-controlled senders with better congestion signals so that flows can achieve link capacity without buffering delay.
> Both are proposing to use ECT(1) as part of the mechanism, but to use it in different ways.

ECT(1) from a unwritten, specialized tcp that is incompatible with
BBR, Cubic, and Reno.

ECT(1) from a well established, shipping AQM.

> SCE’s usage of ECT(1) potentially allows an automatic fallback to traditional Cubic behavior if the bottleneck link is a single-queue classic-ECN AQM (do any of these exist?), whereas L4S will need to detect such a condition via RTT measurement

Strike "potentially". Does. Instead of writing further emails, I'm
focusing on patching tcptrace and xplot to show this clearly from
packet captures. Perhaps that will be ready by the hackathon.

> L4S’s usage of ECT(1) allows links to identify new senders and take advantage of new sender features like reordering tolerance that can further drive down latency in many common link technologies.

There's nothing in SCE that stops the exact same idea, except that the
behavior is chosen reciever side, not sender side.

> SCE will only work if the bottleneck link implements fq.  Some bottleneck network gear will not be able to implement fq or will not implement it due to its undesirable side effects (see section 6 of RFC 8290).

This is overbroad.

And I didn't write that section.

> L4S will work if the bottleneck link implements *either* fq or dual queue.

And this is not a demonstrated fact yet - *at all*  that needs to
yield to experiment and independent analysis.

That's a good start actually to writing up a good comparison document.
I'll save that and work on it, if
I get a talk slot for it.

>
>
> Beyond that, they are *very,very* similar.

Yes!

>
>
>
> But, L4S has been demonstrated in real equipment and in simulation, and leverages an existing congestion

Not under circumstances I can control. That's Not Science.

>controller that is available in Linux and Windows (with some tweaks).

SCE improves on an existing AQM that the default in roughly 100% of
linux deployments now, all the way up to the new RHEL8 release, which
was the last distro to adopt it, so far as I know. It doesn't require
a specialized tcp to use, either.

>  SCE leverages a paragraph in a draft that describes a first guess about how a congestion controller might work.

We were kind of in a hurry. 'round here, we usually write the code and
test it thoroughly for years, before submitting a draft.

We did part of this work originally with the original definition of
ce_threshold (back in 2013?) when we too had fiddled with DCTCP,
before pacing and BBR had arrived.

Running code is up on several servers now and we hope to have a live
test over the internet at ietf. Maybe tcp-fu will land. Hopefully
tcp-prague will land.

>
>
>
> L4S has defined a congestion feedback mechanism so that these congestion signals can get back to the sender.  SCE offers that “we’ll propose something later”.
>
>
>
> BBR currently does not listen to explicit congestion signals, but it could be updated to do so (for either SCE or L4S).
>
>
>
> -Greg
>
>
>
>
>
> From: Bloat <bloat-bounces@lists.bufferbloat.net> on behalf of "David P. Reed" <dpreed@deepplum.com>
> Date: Sunday, March 17, 2019 at 12:07 PM
> To: Vint Cerf <vint@google.com>
> Cc: bloat <bloat@lists.bufferbloat.net>, "ecn-sane@lists.bufferbloat.net" <ecn-sane@lists.bufferbloat.net>
> Subject: Re: [Bloat] [Ecn-sane] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104
>
>
>
> Vint -
>
>
>
> BBR is the end-to-end control logic that adjusts the source rate to match the share of the bolttleneck link it should use.
>
>
>
> It depends on getting reliable current congestion information via packet drops and/or ECN.
>
>
>
> So the proposal by these guys (not the cable guys) is an attempt to improve the quality of the congestion signal inserted by the router with the bottleneck outbound link.
>
>
>
> THe cable guys are trying to get a "private" field in the IP header for their own use.
>
>
>
>
>
> -----Original Message-----
> From: "Vint Cerf" <vint@google.com>
> Sent: Saturday, March 16, 2019 5:57pm
> To: "Holland, Jake" <jholland@akamai.com>
> Cc: "Mikael Abrahamsson" <swmike@swm.pp.se>, "David P. Reed" <dpreed@deepplum.com>, "ecn-sane@lists.bufferbloat.net" <ecn-sane@lists.bufferbloat.net>, "bloat" <bloat@lists.bufferbloat.net>
> Subject: Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104
>
> where does BBR fit into all this?
>
> v
>
>
>
> On Sat, Mar 16, 2019 at 5:39 PM Holland, Jake <jholland@akamai.com> wrote:
>
> On 2019-03-15, 11:37, "Mikael Abrahamsson" <swmike@swm.pp.se> wrote:
>     L4S has a much better possibility of actually getting deployment into the
>     wider Internet packet-moving equipment than anything being talked about
>     here. Same with PIE as opposed to FQ_CODEL. I know it's might not be as
>     good, but it fits better into actual silicon and it's being proposed by
>     people who actually have better channels into the people setting hard
>     requirements.
>
>     I suggest you consider joining them instead of opposing them.
>
>
> Hi Mikael,
>
> I agree it makes sense that fq_anything has issues when you're talking
> about the OLT/CMTS/BNG/etc., and I believe it when you tell me PIE
> makes better sense there.
>
> But fq_x makes great sense and provides real value for the uplink in a
> home, small office, coffee shop, etc. (if you run the final rate limit
> on the home side of the access link.)  I'm thinking maybe there's a
> disconnect here driven by the different use cases for where AQMs can go.
>
> The thing is, each of these is the most likely congestion point at
> different times, and it's worthwhile for each of them to be able to
> AQM (and mark packets) under congestion.
>
> One of the several things that bothers me with L4S is that I've seen
> precious little concern over interfering with the ability for another
> different AQM in-path to mark packets, and because it changes the
> semantics of CE, you can't have both working at the same time unless
> they both do L4S.
>
> SCE needs a lot of details filled in, but it's so much cleaner that it
> seems to me there's reasonably obvious answers to all (or almost all) of
> those detail questions, and because the semantics are so much cleaner,
> it's much easier to tell it's non-harmful.
>
> <aside regarding="non-harmful">
> The point you raised in another thread about reordering is mostly
> well-taken, and a good counterpoint to the claim "non-harmful relative
> to L4S".
>
> To me it seems sad and dumb that switches ended up trying to make
> ordering guarantees at cost of switching performance, because if it's
> useful to put ordering in the switch, then it must be equally useful to
> put it in the receiver's NIC or OS.
>
> So why isn't it in all the receivers' NIC or OS (where it would render
> the switch's ordering efforts moot) instead of in all the switches?
>
> I'm guessing the answer is a competition trap for the switch vendors,
> plus "with ordering goes faster than without, when you benchmark the
> switch with typical load and current (non-RACK) receivers".
>
> If that's the case, it seems like the drive for a competitive advantage
> caused deployment of a packet ordering workaround in the wrong network
> location(s), out of a pure misalignment of incentives.
>
> RACK rates to fix that in the end, but a lot of damage is already done,
> and the L4S approach gives switches a flag that can double as proof that
> RACK is there on the receiver, so they can stop trying to order those
> packets.
>
> So point granted, I understand and agree there's a cost to abandoning
> that advantage.
> </aside>
>
> But as you also said so well in another thread, this is important.  ("The
> last unicorn", IIRC.)  How much does it matter if there's a feature that
> has value today, but only until RACK is widely deployed?  If you were
> convinced RACK would roll out everywhere within 3 years and SCE would
> produce better results than L4S over the following 15 years, would that
> change your mind?
>
> It would for me, and that's why I'd like to see SCE explored before
> making a call.  I think at its core, it provides the same thing L4S does
> (a high-fidelity explicit congestion signal for the sender), but with
> much cleaner semantics that can be incrementally added to congestion
> controls that people are already using.
>
> Granted, it still remains to be seen whether SCE in practice can match
> the results of L4S, and L4S was here first.  But it seems to me L4S comes
> with some problems that have not yet been examined, and that are nicely
> dodged by a SCE-based approach.
>
> If L4S really is as good as they seem to think, I could imagine getting
> behind it, but I don't think that's proven yet.  I'm not certain, but
> all the comparative analyses I remember seeing have been from more or
> less the same team, and I'm not convinced they don't have some
> misaligned incentives of their own.
>
> I understand a lot of work has gone into L4S, but this move to jump it
> from interesting experiment to de-facto standard without a more critical
> review that digs deeper into some of the potential deployment problems
> has me concerned.
>
> If it really does turn out to be good enough to be permanent, I'm not
> opposed to it, but I'm just not convinced that it's non-harmful, and my
> default position is that the cleaner solution is going to be better in
> the long run, if they can do the same job.
>
> It's not that I want it to be a fight, but I do want to end up with the
> best solution we can get.  We only have the one internet.
>
> Just my 2c.
>
> -Jake
>
>
> _______________________________________________
> Ecn-sane mailing list
> Ecn-sane@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/ecn-sane
>
>
> --
>
> New postal address:
>
> Google
>
> 1875 Explorer Street, 10th Floor
>
> Reston, VA 20190
>
> _______________________________________________
> Bloat mailing list
> Bloat@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/bloat



-- 

Dave Täht
CTO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-831-205-9740

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Sebastian Moeller]

Dear All,


> On Mar 20, 2019, at 00:59, Dave Taht <dave.taht@gmail.com> wrote:
> 
> On Tue, Mar 19, 2019 at 5:44 AM Greg White <g.white@cablelabs.com> wrote:
>> [...]
>> But, L4S has been demonstrated in real equipment and in simulation, and leverages an existing congestion
> 
> Not under circumstances I can control. That's Not Science.
[...]

It would be great if the L4S project maybe could help kick-start independent testing, by creating an sharing two VMs one with the appropriate client side patches and one with a L4S aware AQM (probably curvy RED to avoid the patent issue, assuming the patent does not cover curvyRED). So that it is easier to "kick" the tiers in a way that tests what the L4S project considers compliant clients/AQM. Personally I am interested to see how robust and reliable the  detection of non-L4S CE sources is and how well the L4S side of the AQM will tolerate CE-marked packets from non-L4S senders, or in other words how well the "isolation" works. And also how L4S endpoints will deal with SCE emitting AQMs on their path.
I admit that I have doubts that ECT(1), basically a single "constellation" of a 2-bit bitfield can serve as a replacement for a single independent bit in a single-bit bit-field, that seems required for real isolation of flows of different ECN-response types.

Best Regards
	Sebastian

Re: [Ecn-sane] [Bloat] [tsvwg] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Sebastian Moeller]

Hi ECN-sane,

I reduced the CC list as I do not expect this to further the discussion much, but since I feel I invested too much time reading the L4S RFCs and papers I still want to air this here to get some feedback.


> On Mar 20, 2019, at 21:55, Greg White <g.white@CableLabs.com> wrote:
> 
> In normal conditions, L4S offers "Maximize Throughput" +  "Minimize Loss" + "Minimize Latency" all at once.  It doesn't require an application to have to make that false choice (hence the name "Low Latency Low Loss Scalable throughput").  
> 
> If an application would prefer to "Minimize Cost", then I suppose it could adjust its congestion control to be less aggressive (assuming it is congestion controlled). Also, as you point out the LEPHB could be an option as well.
> 
> What section 4.1 in the dualq draft is referring to is a case where the system needs to protect against unresponsive, overloading flows in the low latency queue.   In that case something has to give (you can't ensure low latency & low loss to e.g. a 100 Mbps unresponsive flow arriving at a 50 Mbps bottleneck).

	Which somewhat puts the claim "ultra-low queueing latency" (see https://tools.ietf.org/html/draft-ietf-tsvwg-l4s-arch-03) into perspective. IMHO, ultra low queueing latency is only going to happen in steady state if effectively pacing senders spread their sending rates such that packets arrive nicely spread out already. I note that with that kind of traffic pattern other AQ would also offer ultra-low queueing latency... I note that "‘Data Centre to the Home’: Ultra-Low Latency for All" states that they see 20ms queue delay with a 7ms base link delay @ 40 Mbps, back of the envelope calculations tell us that at that rate ((40 * 1000^2) / (1538 * 8)) * 0.02 = 65 packets will be paced out of the dualpi2 AQM add 65 more on the L4S side and queuing delay will be at 40ms. Switching to a pacing and less aggressive TCP version helps to smooth out the steady-stae bursts, but will do zilch for transients due to an increase in the number of active flows. 

I wonder how this is going to behave once we have new flows come in at a high rate (at  3.251 KHz capacity adding loads at 100 Hz does not seem like that a heavy load to me especially given)  (actually I don't wonder, the dual-AQM draft indicates that the queue will grow to 250ms and tail dropping will start). If I would be responsible at IETFI really would want to see some analysis of resistance against adversarial traffic patterns before going that route, especially in the light of the fuzzy classification vie ECT(1).

Best Regards
	Sebastian


> 
> -Greg
> 
> 
> 
> 
> On 3/20/19, 2:05 PM, "Bloat on behalf of Jonathan Morton" <bloat-bounces@lists.bufferbloat.net on behalf of chromatix99@gmail.com> wrote:
> 
>> On 20 Mar, 2019, at 9:39 pm, Gorry Fairhurst <gorry@erg.abdn.ac.uk> wrote:
>> 
>> Concerning "Maximize Throughput", if you don't need scalability to very high rates, then is your requirement met by TCP-like semantics, as in TCP with SACK/loss or even better TCP with ABE/ECT(0)?
> 
>    My intention with "Maximise Throughput" is to support the bulk-transfer applications that TCP is commonly used for today.  In Diffserv terminology, you may consider it equivalent to "Best Effort".
> 
>    As far as I can see, L4S offers "Maximise Throughput" and "Minimise Latency" services, but not the other two.
> 
>     - Jonathan Morton
> 
>    _______________________________________________
>    Bloat mailing list
>    Bloat@lists.bufferbloat.net
>    https://lists.bufferbloat.net/listinfo/bloat
> 
> 
> _______________________________________________
> Bloat mailing list
> Bloat@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/bloat

Re: [Ecn-sane] [Bloat] [tsvwg] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Jonathan Morton]

> On 21 Mar, 2019, at 12:12 am, Sebastian Moeller <moeller0@gmx.de> wrote:
> 
> they see 20ms queue delay with a 7ms base link delay @ 40 Mbps

At 40Mbps you might as well be running Cake, and thereby getting 1ms inter-flow induced delay; an order of magnitude better.  And we achieved that o a shoestring budget while they were submarining for a patent application.

If we're supposed to be impressed…

 - Jonathan Morton

Re: [Ecn-sane] [Bloat] [tsvwg] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Sebastian Moeller]

> On Mar 20, 2019, at 23:31, Jonathan Morton <chromatix99@gmail.com> wrote:
> 
>> On 21 Mar, 2019, at 12:12 am, Sebastian Moeller <moeller0@gmx.de> wrote:
>> 
>> they see 20ms queue delay with a 7ms base link delay @ 40 Mbps
> 
> At 40Mbps you might as well be running Cake, and thereby getting 1ms inter-flow induced delay; an order of magnitude better.  And we achieved that o a shoestring budget while they were submarining for a patent application.
> 
> If we're supposed to be impressed…

Nah, there is this GEM:


Comparing Experiments 5, 7 with 6, 8, we can again conclude that our DualQ AQM very much approximates the fq CoDel AQM without the need for flow identi- fication and more complex processing. The main ad- vantage is DualQ’s lower queuing delay for L4S traffic.

So for normal traffic is is worse than fq_codel and better for traffic that does behave TCP-friendly, for which it was bespoke made. So at least they shoud have pimped fq_codel/cake to emit their required CE marking regime and do a test against that, if the goal is to compare apples and apples. I note that they do come into this with a grudge against fq "Per-flow queuing:  Similarly per-flow queuing is not incompatible with the L4S approach.  However, one queue for every flow can be thought of as overkill compared to the minimum of two queues for 
all traffic needed for the L4S approach.  The overkill of per-flow queuing has side-effects:" followed by a list of 4 more or less straw-man arguments. Heck these might be actually reasonable arguments at their core, but the short description in the RFC is fishy.
I believe the coupling between the two queues to be clever and elegant, but the whole premise seems odd to me. What they should have done, IMHO is teach their AQM something like SCE so it can easily react to CE and drops in a standard compliant TCP-friendly fashion, and only do the clever window/rate adjustments if the AQM signals ECT(1), add fair queueing to separate the different TCP variants behavior from each other, and bang no classification bit needed. And no patent (assuming the patent covers the coupling between the two queues)... I am sure I am missing something here, it can not be that simple.


Best Regards
	Sebastian

P.S.: How did the SCE-Talk go, interesting feed-back and discussions?



> 
> - Jonathan Morton
> 

Re: [Ecn-sane] [Bloat] [tsvwg] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Jonathan Morton]

> On 21 Mar, 2019, at 12:56 am, Sebastian Moeller <moeller0@gmx.de> wrote:
> 
> What they should have done, IMHO is teach their AQM something like SCE so it can easily react to CE and drops in a standard compliant TCP-friendly fashion, and only do the clever window/rate adjustments if the AQM signals ECT(1)…

It's not even hard to teach DCTCP to respect SCE, as far as I can tell.  All you have to do is start with a clean copy of NewReno with ABC, then subtract half of all SCE-marked bytes from the cwnd.  That really is it.

 - Jonathan Morton

Re: [Ecn-sane] [Bloat] [tsvwg] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Holland, Jake]

I think it's a fair point that even as close as the non-home side
of the access network, fq would need a lot of queues, and if you
want something in hardware it's going to be tricky.  I hear
they're up to an average of ~6k homes per OLT.

I don't think the default assumption here should be that they
missed something obvious, but rather that they're trying to
solve a hard problem, and something with a classifier has a
legitimate value.

The question to me is about how much it breaks other things to
extract that value, and how much you get out of it in the end.  If
you need fq and therefore the only viable place for AQM with good
results is on the home side of the router, that's got some bad
deployment problems too.

Just my 2c.

-Jake

On 2019-03-20, 15:56, "Sebastian Moeller" <moeller0@gmx.de> wrote:

    
    
    > On Mar 20, 2019, at 23:31, Jonathan Morton <chromatix99@gmail.com> wrote:
    > 
    >> On 21 Mar, 2019, at 12:12 am, Sebastian Moeller <moeller0@gmx.de> wrote:
    >> 
    >> they see 20ms queue delay with a 7ms base link delay @ 40 Mbps
    > 
    > At 40Mbps you might as well be running Cake, and thereby getting 1ms inter-flow induced delay; an order of magnitude better.  And we achieved that o a shoestring budget while they were submarining for a patent application.
    > 
    > If we're supposed to be impressed…
    
    Nah, there is this GEM:
    
    
    Comparing Experiments 5, 7 with 6, 8, we can again conclude that our DualQ AQM very much approximates the fq CoDel AQM without the need for flow identi- fication and more complex processing. The main ad- vantage is DualQ’s lower queuing delay for L4S traffic.
    
    So for normal traffic is is worse than fq_codel and better for traffic that does behave TCP-friendly, for which it was bespoke made. So at least they shoud have pimped fq_codel/cake to emit their required CE marking regime and do a test against that, if the goal is to compare apples and apples. I note that they do come into this with a grudge against fq "Per-flow queuing:  Similarly per-flow queuing is not incompatible with the L4S approach.  However, one queue for every flow can be thought of as overkill compared to the minimum of two queues for 
    all traffic needed for the L4S approach.  The overkill of per-flow queuing has side-effects:" followed by a list of 4 more or less straw-man arguments. Heck these might be actually reasonable arguments at their core, but the short description in the RFC is fishy.
    I believe the coupling between the two queues to be clever and elegant, but the whole premise seems odd to me. What they should have done, IMHO is teach their AQM something like SCE so it can easily react to CE and drops in a standard compliant TCP-friendly fashion, and only do the clever window/rate adjustments if the AQM signals ECT(1), add fair queueing to separate the different TCP variants behavior from each other, and bang no classification bit needed. And no patent (assuming the patent covers the coupling between the two queues)... I am sure I am missing something here, it can not be that simple.
    
    
    Best Regards
    	Sebastian
    
    P.S.: How did the SCE-Talk go, interesting feed-back and discussions?
    
    
    
    > 
    > - Jonathan Morton
    > 
    
    _______________________________________________
    Bloat mailing list
    Bloat@lists.bufferbloat.net
    https://lists.bufferbloat.net/listinfo/bloat
    

Re: [Ecn-sane] [Bloat] [tsvwg] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Jonathan Morton]

> On 21 Mar, 2019, at 1:11 am, Holland, Jake <jholland@akamai.com> wrote:
> 
> I think it's a fair point that even as close as the non-home side
> of the access network, fq would need a lot of queues, and if you
> want something in hardware it's going to be tricky.  I hear
> they're up to an average of ~6k homes per OLT.

I think most of us would be relieved if competent single-queue AQMs became ubiquitous.  It doesn't have to be Cake everywhere, just *something* unambiguously better than a dumb FIFO - and that's a rather low bar to clear.

Now, when you have a 6000-channel router, I expect it starts with some very simple and fast device to direct packets in *approximately* the right direction, where some other piece of hardware deals with some subset of the total port count.  Let's say you have a 1Gbps+ link to a 64-line cluster.  Immediately the problem of providing FQ on each of those lines is more tractable; you can give each one 1024 queues and AQMs, the same as fq_codel, for a quite manageable total of 65536, and it's not so hard to build hardware that can keep up with 1Gbps traffic these days.

 - Jonathan Morton

Re: [Ecn-sane] [Bloat] [tsvwg] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Mikael Abrahamsson]

On Thu, 21 Mar 2019, Jonathan Morton wrote:

> Now, when you have a 6000-channel router, I expect it starts with some 
> very simple and fast device to direct packets in *approximately* the 
> right direction, where some other piece of hardware deals with some 
> subset of the total port count.  Let's say you have a 1Gbps+ link to a 
> 64-line cluster.  Immediately the problem of providing FQ on each of 
> those lines is more tractable; you can give each one 1024 queues and 
> AQMs, the same as fq_codel, for a quite manageable total of 65536, and 
> it's not so hard to build hardware that can keep up with 1Gbps traffic 
> these days.

I don't know the actual cost of having a high queue number router, I just 
know that to currently buy these in the market there is something around a 
magnitude difference in cost of buying something with 8 queues per port or 
128k queues per port.

The PON OLT is sometimes a smallish device that might need to be 
temperature hardened and required to be low power, because it's sitting in 
a roadside cabinet or something. The problem here is that you're asking 
for a major re-design of how this is done to a group of people that don't 
have on the radar that what you're talking about is a serious problem to 
solve.

As you said in an earlier email, we're in stupid large FIFO territory a 
lot of the time, and even configuring WRED on existing equipment properly 
would be a big improvement for the end users, and not even this is done.

I am attending my first BBF meeting ever. Just to give an example of how 
networks are often built by the largest operators, you can look at 
http://www.ieee1904.org/events/2014_06_workshop/s2_alter_access.pdf slide 
"TR-156 and TR-200: GPON and EPON access"

In this case, queueing might happen at so many places along the packet 
path and different encapsulations that it's really really hard (and 
costly) to change things to do proper FQ. If we look at the BNG->eth 
egg->OLT->ONT->RG packet path, typically queueing might happen at the BNG, 
but in case of high usage you might have queueing in the OLT->ONT, and the 
OLT just isn't looking into the PPPoE payload to be able to do FQ there.

I might not agree with how these people decide networks should be built, 
but that's unfortunately the way things look in a lot of cases. Telling 
them to just do "FQ, how hard can it be?". Typically, the answer is "hard, 
for a multitude of reasons".

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se

Re: [Ecn-sane] [Bloat] [tsvwg] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Mikael Abrahamsson]

On Thu, 21 Mar 2019, Mikael Abrahamsson wrote:

> I might not agree with how these people decide networks should be built, 
> but that's unfortunately the way things look in a lot of cases. Telling 
> them to just do "FQ, how hard can it be?". Typically, the answer is 
> "hard, for a multitude of reasons".

Btw, in 
http://1ukcym66nom10cmylunctf84-wpengine.netdna-ssl.com/wp-content/uploads/2018/11/TR-156_Issue-2-1.pdf 
5.2.x you can see how scheduling is done. If you'd like something like 
that changed then anything new needs to go into documents like these in 
order to get further deplyment.

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se

Re: [Ecn-sane] [Bloat] [tsvwg] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Sebastian Moeller]

Hi Jake,


> On Mar 21, 2019, at 00:11, Holland, Jake <jholland@akamai.com> wrote:
> 
> I think it's a fair point that even as close as the non-home side
> of the access network, fq would need a lot of queues, and if you
> want something in hardware it's going to be tricky.  I hear
> they're up to an average of ~6k homes per OLT.

	Except they state "In practice it would also be important to de- ploy AQM in the residential gateway, but to minimise side-effects we kept upstream traffic below capacity." meaning in addition to the OLT/BNG/whatever shaper they also envision a shaper on the CPE. And I believe there is ample evidence (in openwrt with sqm-scripts) that in that case the downstream shaper can also be put on the CPE with reasonable success. 


> 
> I don't think the default assumption here should be that they
> missed something obvious, but rather that they're trying to
> solve a hard problem, and something with a classifier has a
> legitimate value.

	I agree, except ECT(1) clearly is a very approximate "classifier" as it can not distinguish the L4S-ness of CE marked packets, which affects both the AQM part which will treat non-L4S traffic as false positive as well as TCP Prague endpoints that will mistreat CE-marked packets as L4S signals even if the CE mark is from a TCP-friendly AQM. I note that neither "‘Data Centre to the Home’: Ultra-Low Latency for All" nor "PI2: A Linearized AQM for both Classic and Scalable TCP" seem to discuss these classification errors and their effects on real traffic in sufficient depth.
It is one thing to soak of one of the last few available "codepoints" in the IP headers, but it is another in my book to do so and not reliably being able to extract the encoded information. At least from my layman's perspective I wonder why this does not seem to bother anybody here?

> 
> The question to me is about how much it breaks other things to
> extract that value, and how much you get out of it in the end.

	That is basically the core of my question above, how much do you get out in the end?

>  If you need fq and therefore the only viable place for AQM with good
> results is on the home side of the router, that's got some bad
> deployment problems too.

	As I state above, even the L4S project position seems to be that AQM on the CPE/router is essential, so we are only haggling about how much AQM needs to be done on the router. But from that perspective, I would not be unhappy if my ISP would employ a lower latency AQM solution upstream of my router than they currently do, sort of as a belt and suspender approach to have my router's back in cases of severe packet inrush.

Best Regards
	Sebastian

> 
> Just my 2c.
> 
> -Jake
> 
> On 2019-03-20, 15:56, "Sebastian Moeller" <moeller0@gmx.de> wrote:
> 
> 
> 
>> On Mar 20, 2019, at 23:31, Jonathan Morton <chromatix99@gmail.com> wrote:
>> 
>>> On 21 Mar, 2019, at 12:12 am, Sebastian Moeller <moeller0@gmx.de> wrote:
>>> 
>>> they see 20ms queue delay with a 7ms base link delay @ 40 Mbps
>> 
>> At 40Mbps you might as well be running Cake, and thereby getting 1ms inter-flow induced delay; an order of magnitude better.  And we achieved that o a shoestring budget while they were submarining for a patent application.
>> 
>> If we're supposed to be impressed…
> 
>    Nah, there is this GEM:
> 
> 
>    Comparing Experiments 5, 7 with 6, 8, we can again conclude that our DualQ AQM very much approximates the fq CoDel AQM without the need for flow identi- fication and more complex processing. The main ad- vantage is DualQ’s lower queuing delay for L4S traffic.
> 
>    So for normal traffic is is worse than fq_codel and better for traffic that does behave TCP-friendly, for which it was bespoke made. So at least they shoud have pimped fq_codel/cake to emit their required CE marking regime and do a test against that, if the goal is to compare apples and apples. I note that they do come into this with a grudge against fq "Per-flow queuing:  Similarly per-flow queuing is not incompatible with the L4S approach.  However, one queue for every flow can be thought of as overkill compared to the minimum of two queues for 
>    all traffic needed for the L4S approach.  The overkill of per-flow queuing has side-effects:" followed by a list of 4 more or less straw-man arguments. Heck these might be actually reasonable arguments at their core, but the short description in the RFC is fishy.
>    I believe the coupling between the two queues to be clever and elegant, but the whole premise seems odd to me. What they should have done, IMHO is teach their AQM something like SCE so it can easily react to CE and drops in a standard compliant TCP-friendly fashion, and only do the clever window/rate adjustments if the AQM signals ECT(1), add fair queueing to separate the different TCP variants behavior from each other, and bang no classification bit needed. And no patent (assuming the patent covers the coupling between the two queues)... I am sure I am missing something here, it can not be that simple.
> 
> 
>    Best Regards
>    	Sebastian
> 
>    P.S.: How did the SCE-Talk go, interesting feed-back and discussions?
> 
> 
> 
>> 
>> - Jonathan Morton
>> 
> 
>    _______________________________________________
>    Bloat mailing list
>    Bloat@lists.bufferbloat.net
>    https://lists.bufferbloat.net/listinfo/bloat
> 
> 

Re: [Ecn-sane] [Bloat] [tsvwg] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Holland, Jake]

Hi Sebastian,

+1 on "approximate classifier" and CE.  This does have me worried,
particularly in the case of multiple AQMs inline.

I think we mostly agree here, and my default position is still
that because SCE is cleaner, I like it better unless L4S can
demonstrate significant value over SCE.

I just wanted to make the point that there's a real chance
L4S might be able to demonstrate significant value that's much
harder to get in some other way (like DSCP), particularly in a
core or closer-to-core device where fq is impractical.

I basically was responding just because I felt like the dismissal
was premature, and seemed to rest on fq being practical in all
AQM cases, which I think is also unproven.  (Even if the OLT can
be solved, I'm willing to stipulate there might be relevant
devices where fq is impractical.)

But I don't mean to argue against the conclusion that SCE seems
more likely to cause fewer problems.  Just that it might be useful
to avoid dismissing legitimate points in L4S's favor.

Best Regards,
Jake

On 2019-03-20, 16:31, "Sebastian Moeller" <moeller0@gmx.de> wrote:

    Hi Jake,
    
    
    > On Mar 21, 2019, at 00:11, Holland, Jake <jholland@akamai.com> wrote:
    > 
    > I think it's a fair point that even as close as the non-home side
    > of the access network, fq would need a lot of queues, and if you
    > want something in hardware it's going to be tricky.  I hear
    > they're up to an average of ~6k homes per OLT.
    
    	Except they state "In practice it would also be important to de- ploy AQM in the residential gateway, but to minimise side-effects we kept upstream traffic below capacity." meaning in addition to the OLT/BNG/whatever shaper they also envision a shaper on the CPE. And I believe there is ample evidence (in openwrt with sqm-scripts) that in that case the downstream shaper can also be put on the CPE with reasonable success. 
    
    
    > 
    > I don't think the default assumption here should be that they
    > missed something obvious, but rather that they're trying to
    > solve a hard problem, and something with a classifier has a
    > legitimate value.
    
    	I agree, except ECT(1) clearly is a very approximate "classifier" as it can not distinguish the L4S-ness of CE marked packets, which affects both the AQM part which will treat non-L4S traffic as false positive as well as TCP Prague endpoints that will mistreat CE-marked packets as L4S signals even if the CE mark is from a TCP-friendly AQM. I note that neither "‘Data Centre to the Home’: Ultra-Low Latency for All" nor "PI2: A Linearized AQM for both Classic and Scalable TCP" seem to discuss these classification errors and their effects on real traffic in sufficient depth.
    It is one thing to soak of one of the last few available "codepoints" in the IP headers, but it is another in my book to do so and not reliably being able to extract the encoded information. At least from my layman's perspective I wonder why this does not seem to bother anybody here?
    
    > 
    > The question to me is about how much it breaks other things to
    > extract that value, and how much you get out of it in the end.
    
    	That is basically the core of my question above, how much do you get out in the end?
    
    >  If you need fq and therefore the only viable place for AQM with good
    > results is on the home side of the router, that's got some bad
    > deployment problems too.
    
    	As I state above, even the L4S project position seems to be that AQM on the CPE/router is essential, so we are only haggling about how much AQM needs to be done on the router. But from that perspective, I would not be unhappy if my ISP would employ a lower latency AQM solution upstream of my router than they currently do, sort of as a belt and suspender approach to have my router's back in cases of severe packet inrush.
    
    Best Regards
    	Sebastian
    
    > 
    > Just my 2c.
    > 
    > -Jake
    > 
    > On 2019-03-20, 15:56, "Sebastian Moeller" <moeller0@gmx.de> wrote:
    > 
    > 
    > 
    >> On Mar 20, 2019, at 23:31, Jonathan Morton <chromatix99@gmail.com> wrote:
    >> 
    >>> On 21 Mar, 2019, at 12:12 am, Sebastian Moeller <moeller0@gmx.de> wrote:
    >>> 
    >>> they see 20ms queue delay with a 7ms base link delay @ 40 Mbps
    >> 
    >> At 40Mbps you might as well be running Cake, and thereby getting 1ms inter-flow induced delay; an order of magnitude better.  And we achieved that o a shoestring budget while they were submarining for a patent application.
    >> 
    >> If we're supposed to be impressed…
    > 
    >    Nah, there is this GEM:
    > 
    > 
    >    Comparing Experiments 5, 7 with 6, 8, we can again conclude that our DualQ AQM very much approximates the fq CoDel AQM without the need for flow identi- fication and more complex processing. The main ad- vantage is DualQ’s lower queuing delay for L4S traffic.
    > 
    >    So for normal traffic is is worse than fq_codel and better for traffic that does behave TCP-friendly, for which it was bespoke made. So at least they shoud have pimped fq_codel/cake to emit their required CE marking regime and do a test against that, if the goal is to compare apples and apples. I note that they do come into this with a grudge against fq "Per-flow queuing:  Similarly per-flow queuing is not incompatible with the L4S approach.  However, one queue for every flow can be thought of as overkill compared to the minimum of two queues for 
    >    all traffic needed for the L4S approach.  The overkill of per-flow queuing has side-effects:" followed by a list of 4 more or less straw-man arguments. Heck these might be actually reasonable arguments at their core, but the short description in the RFC is fishy.
    >    I believe the coupling between the two queues to be clever and elegant, but the whole premise seems odd to me. What they should have done, IMHO is teach their AQM something like SCE so it can easily react to CE and drops in a standard compliant TCP-friendly fashion, and only do the clever window/rate adjustments if the AQM signals ECT(1), add fair queueing to separate the different TCP variants behavior from each other, and bang no classification bit needed. And no patent (assuming the patent covers the coupling between the two queues)... I am sure I am missing something here, it can not be that simple.
    > 
    > 
    >    Best Regards
    >    	Sebastian
    > 
    >    P.S.: How did the SCE-Talk go, interesting feed-back and discussions?
    > 
    > 
    > 
    >> 
    >> - Jonathan Morton
    >> 
    > 
    >    _______________________________________________
    >    Bloat mailing list
    >    Bloat@lists.bufferbloat.net
    >    https://lists.bufferbloat.net/listinfo/bloat
    > 
    > 
    
    

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Jonathan Morton]

> On 16 Mar, 2019, at 11:38 pm, Holland, Jake <jholland@akamai.com> wrote:
> 
> SCE needs a lot of details filled in, but it's so much cleaner that it
> seems to me there's reasonably obvious answers to all (or almost all) of
> those detail questions, and because the semantics are so much cleaner,
> it's much easier to tell it's non-harmful.

And we're actively working on filling in those details.  They haven't yet made it as far as an I-D, partly because we'd like to do at least some preliminary testing first.

> where does BBR fit into all this?

The present version of BBR, which I've actually seen, ignores ECN completely.  I'm told that the new version which I haven't yet seen, does *something* with ECN, but I'm unclear on what.  I think it'll be up to the BBR developers to decide how to incorporate SCE information, using conventional TCPs as a guide as to what is reasonable - or to ignore it, which is also a valid design choice.

 - Jonathan Morton

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Sebastian Moeller]

> On Mar 16, 2019, at 22:38, Holland, Jake <jholland@akamai.com> wrote:
> 
> On 2019-03-15, 11:37, "Mikael Abrahamsson" <swmike@swm.pp.se> wrote:
>    L4S has a much better possibility of actually getting deployment into the 
>    wider Internet packet-moving equipment than anything being talked about 
>    here. Same with PIE as opposed to FQ_CODEL. I know it's might not be as 
>    good, but it fits better into actual silicon and it's being proposed by 
>    people who actually have better channels into the people setting hard 
>    requirements.
> 
>    I suggest you consider joining them instead of opposing them.
> 
> 
> Hi Mikael,
> 
> I agree it makes sense that fq_anything has issues when you're talking
> about the OLT/CMTS/BNG/etc., and I believe it when you tell me PIE
> makes better sense there.

	Except PIE is not mandatory there, DOCSIS3.1 made PIE mandatory on the CPE or customer modems, CMTS AQM was I believe recommended.

> 
> But fq_x makes great sense and provides real value for the uplink in a
> home, small office, coffee shop, etc. (if you run the final rate limit
> on the home side of the access link.)  I'm thinking maybe there's a
> disconnect here driven by the different use cases for where AQMs can go.
> 
> The thing is, each of these is the most likely congestion point at
> different times, and it's worthwhile for each of them to be able to
> AQM (and mark packets) under congestion.
> 
> One of the several things that bothers me with L4S is that I've seen
> precious little concern over interfering with the ability for another
> different AQM in-path to mark packets, and because it changes the
> semantics of CE, you can't have both working at the same time unless
> they both do L4S.

The relevant section from https://tools.ietf.org/html/draft-ietf-tsvwg-ecn-l4s-id-06:


"A.1.4.  Fall back to Reno-friendly congestion control on classic ECN

        bottlenecks

   Description: A scalable congestion control needs to react to ECN
   marking from a non-L4S but ECN-capable bottleneck in a way that will
   coexist with a TCP Reno congestion control [RFC5681].

   Motivation: Similarly to the requirement in Appendix A.1.3, this
   requirement is a safety condition to ensure a scalable congestion
   control behaves properly when it builds a queue at a network
   bottleneck that has not been upgraded to support L4S.  On detecting
   classic ECN marking (see below), a scalable congestion control will
   need to fall back to classic congestion control behaviour.  If it
   does not comply with this requirement it could starve classic
   traffic.

   It would take time for endpoints to distinguish classic and L4S ECN
   marking.  An increase in queuing delay or in delay variation would be
   a tell-tale sign, but it is not yet clear where a line would be drawn
   between the two behaviours.  It might be possible to cache what was
   learned about the path to help subsequent attempts to detect the type
   of marking."


In short L4S has not seem to have solved this problem yet except for identifying it.
IMHO this is a clear reason not to to re-use ECT(1) outside of ECN signaling.


> 
> SCE needs a lot of details filled in, but it's so much cleaner that it
> seems to me there's reasonably obvious answers to all (or almost all) of
> those detail questions, and because the semantics are so much cleaner,
> it's much easier to tell it's non-harmful.

	IMHO the beauty of the simple SCE proposal is that it simply supplies information a rational flow could/should react on purely by self interest, but ignoring it should do no harm, assuming the assumption holds that ECT(1) safely traverses the internet.

> 
> <aside regarding="non-harmful">
> The point you raised in another thread about reordering is mostly
> well-taken, and a good counterpoint to the claim "non-harmful relative
> to L4S".

	Would this not be better handled by a dedicated signal instead of assuming all L4S traffic is re-ordering tolerant (which as seen from my vantage point runs counter L4S goal of ultra-low latency).


> 
> To me it seems sad and dumb that switches ended up trying to make
> ordering guarantees at cost of switching performance, because if it's
> useful to put ordering in the switch, then it must be equally useful to
> put it in the receiver's NIC or OS.

	The issue I see, is that re-ordering with fast ARQ cycles on a fast link will be faster than pushing the un-ordered packets over the bottleneck access link, as in the case of data stretching over multiple packets the user might need them all before the data can be actually used.

> 
> So why isn't it in all the receivers' NIC or OS (where it would render
> the switch's ordering efforts moot) instead of in all the switches?
> 
> I'm guessing the answer is a competition trap for the switch vendors,
> plus "with ordering goes faster than without, when you benchmark the
> switch with typical load and current (non-RACK) receivers".
> 
> If that's the case, it seems like the drive for a competitive advantage
> caused deployment of a packet ordering workaround in the wrong network
> location(s), out of a pure misalignment of incentives.
> 
> RACK rates to fix that in the end, but a lot of damage is already done,
> and the L4S approach gives switches a flag that can double as proof that
> RACK is there on the receiver, so they can stop trying to order those
> packets.
> 
> So point granted, I understand and agree there's a cost to abandoning
> that advantage.
> </aside>
> 
> But as you also said so well in another thread, this is important.  ("The
> last unicorn", IIRC.)  How much does it matter if there's a feature that
> has value today, but only until RACK is widely deployed?  If you were
> convinced RACK would roll out everywhere within 3 years and SCE would
> produce better results than L4S over the following 15 years, would that
> change your mind?
> 
> It would for me, and that's why I'd like to see SCE explored before
> making a call.  I think at its core, it provides the same thing L4S does
> (a high-fidelity explicit congestion signal for the sender), but with
> much cleaner semantics that can be incrementally added to congestion
> controls that people are already using.
> 
> Granted, it still remains to be seen whether SCE in practice can match
> the results of L4S, and L4S was here first.  But it seems to me L4S comes
> with some problems that have not yet been examined, and that are nicely
> dodged by a SCE-based approach.
> 
> If L4S really is as good as they seem to think, I could imagine getting
> behind it, but I don't think that's proven yet.  I'm not certain, but
> all the comparative analyses I remember seeing have been from more or
> less the same team, and I'm not convinced they don't have some
> misaligned incentives of their own.
> 
> I understand a lot of work has gone into L4S, but this move to jump it
> from interesting experiment to de-facto standard without a more critical
> review that digs deeper into some of the potential deployment problems
> has me concerned.
> 
> If it really does turn out to be good enough to be permanent, I'm not
> opposed to it, but I'm just not convinced that it's non-harmful, and my
> default position is that the cleaner solution is going to be better in
> the long run, if they can do the same job.
> 
> It's not that I want it to be a fight, but I do want to end up with the
> best solution we can get.  We only have the one internet.
> 
> Just my 2c.  
> 
> -Jake
> 
> 
> _______________________________________________
> Ecn-sane mailing list
> Ecn-sane@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/ecn-sane

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Mikael Abrahamsson]

On Sat, 16 Mar 2019, Holland, Jake wrote:

> Granted, it still remains to be seen whether SCE in practice can match
> the results of L4S, and L4S was here first.  But it seems to me L4S comes
> with some problems that have not yet been examined, and that are nicely
> dodged by a SCE-based approach.

I'm actually not that interested in an academic competition about what 
solution gives the ultimate "best" outcome in simulation or in a lab.

I am interested in good enough solutions that are actually deployable and 
will get deployed, and doesn't have any pathological behaviour when it 
comes to legacy traffic.

Right now the Internet is full of deep FIFOs and they're not going away, 
and they're not getting FQ_CODEL or CAKE.

CAKE/FQ_CODEL is nice, but it's not being deployed at the typical 
congestion points we have in real life. These devices would have a much 
easier time getting PIE or even RED, if it was just implemented.

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Loganaden Velvindron]

On Sun, Mar 17, 2019 at 6:06 PM Mikael Abrahamsson <swmike@swm.pp.se> wrote:
>
> On Sat, 16 Mar 2019, Holland, Jake wrote:
>
> > Granted, it still remains to be seen whether SCE in practice can match
> > the results of L4S, and L4S was here first.  But it seems to me L4S comes
> > with some problems that have not yet been examined, and that are nicely
> > dodged by a SCE-based approach.
>
> I'm actually not that interested in an academic competition about what
> solution gives the ultimate "best" outcome in simulation or in a lab.
>
> I am interested in good enough solutions that are actually deployable and
> will get deployed, and doesn't have any pathological behaviour when it
> comes to legacy traffic.
>
> Right now the Internet is full of deep FIFOs and they're not going away,
> and they're not getting FQ_CODEL or CAKE.
>
> CAKE/FQ_CODEL is nice, but it's not being deployed at the typical
> congestion points we have in real life. These devices would have a much
> easier time getting PIE or even RED, if it was just implemented.
>

is there an open source implementation of PIE which is close to what
is used by the DOCSIS modems ?

> --
> Mikael Abrahamsson    email: swmike@swm.pp.se
> _______________________________________________
> Ecn-sane mailing list
> Ecn-sane@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/ecn-sane

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Toke Høiland-Jørgensen]

On 17 March 2019 18:37:27 CET, Loganaden Velvindron <loganaden@gmail.com> wrote:
>On Sun, Mar 17, 2019 at 6:06 PM Mikael Abrahamsson <swmike@swm.pp.se>
>wrote:
>>
>> On Sat, 16 Mar 2019, Holland, Jake wrote:
>>
>> > Granted, it still remains to be seen whether SCE in practice can
>match
>> > the results of L4S, and L4S was here first.  But it seems to me L4S
>comes
>> > with some problems that have not yet been examined, and that are
>nicely
>> > dodged by a SCE-based approach.
>>
>> I'm actually not that interested in an academic competition about
>what
>> solution gives the ultimate "best" outcome in simulation or in a lab.
>>
>> I am interested in good enough solutions that are actually deployable
>and
>> will get deployed, and doesn't have any pathological behaviour when
>it
>> comes to legacy traffic.
>>
>> Right now the Internet is full of deep FIFOs and they're not going
>away,
>> and they're not getting FQ_CODEL or CAKE.
>>
>> CAKE/FQ_CODEL is nice, but it's not being deployed at the typical
>> congestion points we have in real life. These devices would have a
>much
>> easier time getting PIE or even RED, if it was just implemented.
>>
>
>is there an open source implementation of PIE which is close to what
>is used by the DOCSIS modems ?

Yup. sch_pie in the Linux kernel. I believe Dave originally helped the Cisco people get it upstream...

There's even an out of tree fq_pie somewhere. Don't have the link handy.

-Toke

>
>> --
>> Mikael Abrahamsson    email: swmike@swm.pp.se
>> _______________________________________________
>> Ecn-sane mailing list
>> Ecn-sane@lists.bufferbloat.net
>> https://lists.bufferbloat.net/listinfo/ecn-sane
>_______________________________________________
>Ecn-sane mailing list
>Ecn-sane@lists.bufferbloat.net
>https://lists.bufferbloat.net/listinfo/ecn-sane

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Mikael Abrahamsson]

On Sun, 17 Mar 2019, Loganaden Velvindron wrote:

> is there an open source implementation of PIE which is close to what is 
> used by the DOCSIS modems ?

PIE was added to the Linux kernel in 3.14 according to 
https://www.linux.com/news/linux-314-release-no-pi-new-pie-fights-bufferbloat

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Dave Taht]

I helped land a more rfc - compliant version of pie into net-next late
last year.

ironically, we had one open bug re ecn -
https://github.com/gautamramk/FQ-PIE-for-Linux-Kernel/issues/2 -
docsis pie supported ecn not at all. I actually hold a good opinion of
pie - it is a good single queue aqm, more responsive to overload than
codel is. Which is why I worked on it to bring it up to spec finally.

Next up was polishing that version of fq-pie for linux inclusion. I
was unsure if it had the same codel-derived rate estimator as the bsd
one, because pie's original estimator fails with many queues. I always
wondered if that behavior would show up also in todays hw (64 on many
10GigE cards).

"Pie was added". Um, er, I (we) worked hard through 7 or so revisions
of the original quite crappy contractor written code, to make it
acceptable for mainline and for test. For free. In terms of billable
time, I was probably out $60k or more.

No "was" there. I know I shouldn't be resenting that phrasing, but I'd
like to obtain some credit for being fair and impartial. Also
thoroughly benchmarked it. and discarded it as I felt that a 5ms codel
target for good queue was better than a 20ms one for pie.

I'd offered multiple times to help fix up the dualpi code, but could
not look at it due to the frand patent, which I asked privately, be
removed.

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Rodney W. Grimes]

> On Sun, Mar 17, 2019 at 6:06 PM Mikael Abrahamsson <swmike@swm.pp.se> wrote:
> >
> > On Sat, 16 Mar 2019, Holland, Jake wrote:
> >
> > > Granted, it still remains to be seen whether SCE in practice can match
> > > the results of L4S, and L4S was here first.  But it seems to me L4S comes
> > > with some problems that have not yet been examined, and that are nicely
> > > dodged by a SCE-based approach.
> >
> > I'm actually not that interested in an academic competition about what
> > solution gives the ultimate "best" outcome in simulation or in a lab.
> >
> > I am interested in good enough solutions that are actually deployable and
> > will get deployed, and doesn't have any pathological behaviour when it
> > comes to legacy traffic.
> >
> > Right now the Internet is full of deep FIFOs and they're not going away,
> > and they're not getting FQ_CODEL or CAKE.
> >
> > CAKE/FQ_CODEL is nice, but it's not being deployed at the typical
> > congestion points we have in real life. These devices would have a much
> > easier time getting PIE or even RED, if it was just implemented.
> >
> 
> is there an open source implementation of PIE which is close to what
> is used by the DOCSIS modems ?

I do not know if it is close to the DOCSIS modems,
but FreeBSD has PIE implemented

/usr/src/sys/netpfil/ipfw/dn_aqm_pie.c
/usr/src/sys/netpfil/ipfw/dn_aqm_pie.h
/usr/src/sys/netpfil/ipfw/dn_sched_fq_pie.c

> > Mikael Abrahamsson    email: swmike@swm.pp.se

-- 
Rod Grimes                                                 rgrimes@freebsd.org

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Luca Muscariello]

[-- Attachment #1: Type: text/plain, Size: 2933 bytes --]

To me there is substantial difference from something like fq_codel or
fq_pie where service differentiation is largely implicit
and approches largely based on explicit marking.

Approaches based on marking face technical and non technical challenges
that have been largely mentioned in these lists.

Fq_codel has a ton of litterature behind both theoretical and experimental
and it is something very close to optimality, in terms of completion time
and latency.

Fq_codel also incentivizes the development of better congestion control as
the reward is immediate. It also makes  Internet performance
predictable.

Once we know that, the logical approach would be to try to approximate that
thing when the full mechanism is not possible because of a variety of
limitations.

This is the case in some DC switches that implement AFD+priority fair
queueing at 40Gbps.

Fq_codel has an outstanding footprint in terms of deployment.
Iliad deployed SFQ in 2005 nation wide and Fq_codel as soon as it was
available in France and is the second largest ISP.
Iliad/Free  controls the development of both the home GW and the DSLAM.
They have recently started to commercialize 10Gbps to the home using
switched Ethernet.
I’m very tempted to test it.

Kudos to them for being able to prove it is possible as long as you control
the development of your equipment.

A logical next step  to me seems to push chipcos to build fq_codel in
silicon.
It is totally feasible.

If on the other hand we say that we can achieve all fq_codel provides with
current chipsets we’ll never create the incentives to make progress.

My2c
Luca

On Sun 17 Mar 2019 at 15:06, Mikael Abrahamsson <swmike@swm.pp.se> wrote:

> On Sat, 16 Mar 2019, Holland, Jake wrote:
>
> > Granted, it still remains to be seen whether SCE in practice can match
> > the results of L4S, and L4S was here first.  But it seems to me L4S comes
> > with some problems that have not yet been examined, and that are nicely
> > dodged by a SCE-based approach.
>
> I'm actually not that interested in an academic competition about what
> solution gives the ultimate "best" outcome in simulation or in a lab.
>
> I am interested in good enough solutions that are actually deployable and
> will get deployed, and doesn't have any pathological behaviour when it
> comes to legacy traffic.
>
> Right now the Internet is full of deep FIFOs and they're not going away,
> and they're not getting FQ_CODEL or CAKE.
>
> CAKE/FQ_CODEL is nice, but it's not being deployed at the typical
> congestion points we have in real life. These devices would have a much
> easier time getting PIE or even RED, if it was just implemented.
>
> --
> Mikael Abrahamsson    email: swmike@swm.pp.se
> _______________________________________________
> Bloat mailing list
> Bloat@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/bloat
>

[-- Attachment #2: Type: text/html, Size: 4131 bytes --]

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Toke Høiland-Jørgensen]

Luca Muscariello <luca.muscariello@gmail.com> writes:

> To me there is substantial difference from something like fq_codel or
> fq_pie where service differentiation is largely implicit
> and approches largely based on explicit marking.
>
> Approaches based on marking face technical and non technical challenges
> that have been largely mentioned in these lists.
>
> Fq_codel has a ton of litterature behind both theoretical and experimental
> and it is something very close to optimality, in terms of completion time
> and latency.
>
> Fq_codel also incentivizes the development of better congestion control as
> the reward is immediate. It also makes  Internet performance
> predictable.
>
> Once we know that, the logical approach would be to try to approximate that
> thing when the full mechanism is not possible because of a variety of
> limitations.
>
> This is the case in some DC switches that implement AFD+priority fair
> queueing at 40Gbps.
>
> Fq_codel has an outstanding footprint in terms of deployment.
> Iliad deployed SFQ in 2005 nation wide and Fq_codel as soon as it was
> available in France and is the second largest ISP.
> Iliad/Free  controls the development of both the home GW and the DSLAM.
> They have recently started to commercialize 10Gbps to the home using
> switched Ethernet.
> I’m very tempted to test it.
>
> Kudos to them for being able to prove it is possible as long as you control
> the development of your equipment.
>
> A logical next step  to me seems to push chipcos to build fq_codel in
> silicon.
> It is totally feasible.
>
> If on the other hand we say that we can achieve all fq_codel provides with
> current chipsets we’ll never create the incentives to make progress.

+100!

-Toke

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Mikael Abrahamsson]

On Sun, 17 Mar 2019, Luca Muscariello wrote:

> Fq_codel has an outstanding footprint in terms of deployment.

No, it doesn't.

> A logical next step  to me seems to push chipcos to build fq_codel in
> silicon.
> It is totally feasible.

... and how do you plan to make that happen?

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Jonathan Morton]

> On 15 Mar, 2019, at 7:01 pm, David P. Reed <dpreed@deepplum.com> wrote:
> 
> > Next up for sce was going to be to find if dctcp could be modified to
> > use it. Also, bittorrent.
> 
> YES! I endorse this message.

Actually, today I was still figuring out how to fit it to CUBIC.  I *think* I've succeeded…

https://github.com/dtaht/bufferbloat-rfcs/blob/master/sce/ELR%20Proposal%203%20(TCP).txt

I recall DCTCP as being singularly built around a distinct setpoint from what either Classic ECN or SCE expects.  So I think I might look at LEDBAT first.

 - Jonathan Morton

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Dave Taht]

On Fri, Mar 15, 2019 at 9:04 PM Jonathan Morton <chromatix99@gmail.com> wrote:
>
> > On 15 Mar, 2019, at 7:01 pm, David P. Reed <dpreed@deepplum.com> wrote:
> >
> > > Next up for sce was going to be to find if dctcp could be modified to
> > > use it. Also, bittorrent.
> >
> > YES! I endorse this message.
>
> Actually, today I was still figuring out how to fit it to CUBIC.  I *think* I've succeeded…
>
> https://github.com/dtaht/bufferbloat-rfcs/blob/master/sce/ELR%20Proposal%203%20(TCP).txt
>
> I recall DCTCP as being singularly built around a distinct setpoint from what either Classic ECN or SCE expects.  So I think I might look at LEDBAT first.

LEDBAT as defined by the ietf is a waste of time, as is it did not deploy.

In terms of dealing with bittorrent, I recommend you look over the UDP
implementation in libutp, and in particular the embedded
implementation in "transmission", which is easier to play with first.
Along the way, getting setsockopt to set the diffserv bits right
finally for libutp would be nice.


>  - Jonathan Morton
>
> _______________________________________________
> Ecn-sane mailing list
> Ecn-sane@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/ecn-sane



-- 

Dave Täht
CTO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-831-205-9740

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Mikael Abrahamsson]

On Fri, 15 Mar 2019, Dave Taht wrote:

> It appears, also, ironically, (I have confirmation from several sources 
> now) that cake, fq_codel and dualpi are now illegal for an ISP to use in 
> their provided equipment under california law. The idea of one day 
> having to appear in court to defend our key algorithms reminds me of the 
> famous john fogerty case where he demonstrated how blues music was made.

I would love to know more about this. Running an AQM on the customer 
access that doesn't prioritize some specific service should be fine, ie it 
doesn't explicitly do something the *customer* doesn't benefit from.

Net neutrality should be about what the ISP does to benefit itself, not 
what is done on the customer access line (the scheduler per customer) that 
just looks at packet flow characteristics and isn't configured to 
prioritize any specific content (src/destination/port etc).

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Jonathan Morton]

> On 15 Mar, 2019, at 3:01 pm, Sebastian Moeller <moeller0@gmx.de> wrote:
> 
> That said, having read through the L4S architecture description and the related appendices of draft-ietf-tsvwg-ecn-l4s-id-05 I came to the conclusion, that this is a mess.
> 
> The L4S project proposes a really wide-ranging change of basically the internet (but allow a concurrent operation with legacy probably to cater to the fact that an internet-wide flag-day seems daunting to organize). But then they chicken out when figuring out how to differentiate between their new and the old by proposing to use ECT(1)…

I think I would be less annoyed by L4S if it proposed to assign a DSCP or three to identify its traffic.  In fact, I'd be interested to hear a defence of why DSCP identification of L4S flows was *not* adopted.  I suspect it would revolve around the widespread practice of re-marking DSCPs by ISPs, which renders DSCP too unreliable for L4S' purposes.

But using the ECN field for this purpose is *also* unreliable, because it is *intended* to be altered on route (in prescribed ways).  In particular, both ECT codepoints can be replaced by CE, erasing the distinction between them when it comes to choosing which half of a "dual queue" AQM to pass it through.  I'm not convinced they've spent very much of the past several years thinking about that.

Fortunately, L4S flows should work with flow-isolating AQMs (including Cake) without modifying the latter, and without needing to specifically identify which flows are L4S or otherwise.  That really says more about the robustness of proper flow isolation than anything else.  But Codel-type AQMs don't provide the ideal ECN signal for L4S (and nor do RED-type AQMs without specific tuning for L4S), and any single-queue AQM is going to end up with L4S flows outcompeting standard ones quite seriously.

Since very little "big iron" hardware supports flow-isolating AQM so far, that puts a damper on any "incremental deployment" argument to be made for L4S, even if they claim their dual-queue AQM is easier to implement at high link rates than full flow isolation.  The fact is that either dual-queue or flow-isolation is required in middleboxes *before* endpoint deployment of L4S can begin.

SCE explicitly avoids these problems, as both SCE-aware endpoints and SCE-aware middleboxes can safely be deployed without waiting for each other.  Work remains on figuring out precisely how SCE information should be produced and consumed, and verifying that the resulting system behaves as intended when fully deployed - but its interaction with existing deployed hardware and software is explicitly defined to be benign.

 - Jonathan Morton

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Sebastian Moeller]

Hi Jonathan,


> On Mar 15, 2019, at 15:27, Jonathan Morton <chromatix99@gmail.com> wrote:
> 
>> On 15 Mar, 2019, at 3:01 pm, Sebastian Moeller <moeller0@gmx.de> wrote:
>> 
>> That said, having read through the L4S architecture description and the related appendices of draft-ietf-tsvwg-ecn-l4s-id-05 I came to the conclusion, that this is a mess.
>> 
>> The L4S project proposes a really wide-ranging change of basically the internet (but allow a concurrent operation with legacy probably to cater to the fact that an internet-wide flag-day seems daunting to organize). But then they chicken out when figuring out how to differentiate between their new and the old by proposing to use ECT(1)…
> 
> I think I would be less annoyed by L4S if it proposed to assign a DSCP or three to identify its traffic.  In fact, I'd be interested to hear a defence of why DSCP identification of L4S flows was *not* adopted.  I suspect it would revolve around the widespread practice of re-marking DSCPs by ISPs, which renders DSCP too unreliable for L4S' purposes.

https://tools.ietf.org/html/draft-ietf-tsvwg-ecn-l4s-id-05 contains a discussion of the alternatives, specifically to your point it argues:
"Appendix B.  Alternative Identifiers
[...]
B.2.  ECN Plus a Diffserv Codepoint (DSCP)


   Definition:

      For packets with a defined DSCP, all codepoints of the ECN field
      (except Not-ECT) would signify alternative L4S semantics to those
      for classic ECN [RFC3168], specifically:

      *  The L4S DSCP would signifiy that the packet came from an L4S-
         capable sender;

      *  ECT(0) and ECT(1) would both signify that the packet was
         travelling between transport endpoints that were both ECN-
         capable;

      *  CE would signify that the packet had been marked by an AQM
         implementing the L4S service.

   Use of a DSCP is the only approach for alternative ECN semantics
   given as an example in [RFC4774].  However, it was perhaps considered
   more for controlled environments than new end-to-end services;

   Cons:

   Consumes DSCP pairs:  A DSCP is obviously not orthogonal to Diffserv.
      Therefore, wherever the L4S service is applied to multiple
      Diffserv scheduling behaviours, it would be necessary to replace
      each DSCP with a pair of DSCPs.

   Uses critical lower-layer header space:  The resulting increased
      number of DSCPs might be hard to support for some lower layer
      technologies, e.g. 802.1p and MPLS both offer only 3-bits for a
      maximum of 8 traffic class identifiers.  Although L4S should
      reduce and possibly remove the need for some DSCPs intended for
      differentiated queuing delay, it will not remove the need for
      Diffserv entirely, because Diffserv is also used to allocate
      bandwidth, e.g. by prioritising some classes of traffic over
      others when traffic exceeds available capacity.

   Not end-to-end (host-network):  Very few networks honour a DSCP set
      by a host.  Typically a network will zero (bleach) the Diffserv
      field from all hosts.  Sometimes networks will attempt to identify
      applications by some form of packet inspection and, based on
      network policy, they will set the DSCP considered appropriate for
      the identified application.  Network-based application
      identification might use some combination of protocol ID, port
      numbers(s), application layer protocol headers, IP address(es),
      VLAN ID(s) and even packet timing.

   Not end-to-end (network-network):  Very few networks honour a DSCP
      received from a neighbouring network.  Typically a network will
      zero (bleach) the Diffserv field from all neighbouring networks at
      an interconnection point.  Sometimes bilateral arrangements are
      made between networks, such that the receiving network remarks
      some DSCPs to those it uses for roughly equivalent services.  The
      likelihood that a DSCP will be bleached or ignored depends on the
      type of DSCP:

      Local-use DSCP:  These tend to be used to implement application-
         specific network policies, but a bilateral arrangement to
         remark certain DSCPs is often applied to DSCPs in the local-use
         range simply because it is easier not to change all of a
         network's internal configurations when a new arrangement is
         made with a neighbour;

      Global-use DSCP:  These do not tend to be honoured across network
         interconnections more than local-use DSCPs.  However, if two
         networks decide to honour certain of each other's DSCPs, the
         reconfiguration is a little easier if both of their globally
         recognised services are already represented by the relevant
         global-use DSCPs.

         Note that today a global-use DSCP gives little more assurance
         of end-to-end service than a local-use DSCP.  In future the
         global-use range might give more assurance of end-to-end
         service than local-use, but it is unlikely that either
         assurance will be high, particularly given the hosts are
         included in the end-to-end path.

   Not all tunnels:  Diffserv codepoints are often not propagated to the
      outer header when a packet is encapsulated by a tunnel header.
      DSCPs are propagated to the outer of uniform mode tunnels, but not
      pipe mode [RFC2983], and pipe mode is fairly common.

   ECN hard in some lower layers::  Because this approach uses both the
      Diffserv and ECN fields, an AQM wil only work at a lower layer if
      both can be supported.  If individual network operators wished to
      deploy an AQM at a lower layer, they would usually propagate an IP
      Diffserv codepoint to the lower layer, using for example IEEE
      802.1p.  However, the ECN capability is harder to propagate down
      to lower layers because few lower layers support it.

   Pros:

   Could migrate to e2e:  If all usage of classic ECN migrates to usage
      of L4S, the DSCP would become redundant, and the ECN capability
      alone could eventually identify L4S packets without the
      interconnection problems of Diffserv detailed above, and without
      having permanently consumed more than one codepoint in the IP
      header.  Although the DSCP does not generally function as an end-
      to-end identifier (see above), it could be used initially by
      individual ISPs to introduce the L4S service for their own locally
      generated traffic;"


In essence, they do not want to deal with the diffserv mess under the end-to-end perspective and making it reliable.


> 
> But using the ECN field for this purpose is *also* unreliable, because it is *intended* to be altered on route (in prescribed ways).  In particular, both ECT codepoints can be replaced by CE, erasing the distinction between them when it comes to choosing which half of a "dual queue" AQM to pass it through.  I'm not convinced they've spent very much of the past several years thinking about that.

	There is also a discussion of this in Appendix B.  Alternative Identifiers, which I will not copy here ;)


> 
> Fortunately, L4S flows should work with flow-isolating AQMs (including Cake) without modifying the latter, and without needing to specifically identify which flows are L4S or otherwise.  That really says more about the robustness of proper flow isolation than anything else.  But Codel-type AQMs don't provide the ideal ECN signal for L4S (and nor do RED-type AQMs without specific tuning for L4S), and any single-queue AQM is going to end up with L4S flows outcompeting standard ones quite seriously.

	Except L$S flows are required to "degrade" to classic congestion contro once they have proof of not being handled by a l4s aware AQM, like real packet drops or ECT(0) + CE...

> 
> Since very little "big iron" hardware supports flow-isolating AQM so far, that puts a damper on any "incremental deployment" argument to be made for L4S, even if they claim their dual-queue AQM is easier to implement at high link rates than full flow isolation.  The fact is that either dual-queue or flow-isolation is required in middleboxes *before* endpoint deployment of L4S can begin.

	Sure, the argument there seems to be that the typical bottleneck seems to be the access link and there the ISP who could controll this might have an interest of making that happen. In that light the involvement of cablelabs actually seems like a good thing, except for the part were they presumably took development underground/out of sight...

> 
> SCE explicitly avoids these problems, as both SCE-aware endpoints and SCE-aware middleboxes can safely be deployed without waiting for each other.  Work remains on figuring out precisely how SCE information should be produced and consumed, and verifying that the resulting system behaves as intended when fully deployed - but its interaction with existing deployed hardware and software is explicitly defined to be benign.

	Sure, I am confident that should SCE prevail here, L4S would find uses for SCE, but that still faces the same roll-out issue...

Best Regards
	Sebastian

> 
> - Jonathan Morton
> 

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Jonathan Morton]

> On 15 Mar, 2019, at 4:44 pm, Sebastian Moeller <moeller0@gmx.de> wrote:
> 
> In essence, they do not want to deal with the diffserv mess under the end-to-end perspective and making it reliable.

Yeah, that's pretty much what I thought.  Diffserv really does need to be fixed sometime.

>> But Codel-type AQMs don't provide the ideal ECN signal for L4S (and nor do RED-type AQMs without specific tuning for L4S), and any single-queue AQM is going to end up with L4S flows outcompeting standard ones quite seriously.
> 
> Except L$S flows are required to "degrade" to classic congestion contro once they have proof of not being handled by a l4s aware AQM, like real packet drops or ECT(0) + CE...

That isn't enough, because ECN AQMs as presently specified won't change ECT(1) to ECT(0) (nor will SCE), and it would require a lot of overload before dropping actually started.  So those signals don't reliably identify a legacy AQM.

> L4S would find uses for SCE, but that still faces the same roll-out issue...

It's not the same roll-out issue, because in an SCE context L4S would have to be legacy-compatible by default, and only employ the "new" behaviour when SCE information appears - the reverse of its present behaviour - which then makes it backwards compatible and incrementally deployable.

The real snag is that DCTCP's setpoint is 2 marks per RTT, which is different from SCE's specified setpoint of 50% packets marked (unless the cwnd is down to 4 packets).  That'd make it difficult for a straight port of DCTCP to SCE to achieve full throughput.

A sane compromise could be for SCE to be marked in the same way as L4S marks CE, and a valid interpretation of SCE to follow the 1/n response of DCTCP.  That would leverage existing TCP-Prague R&D, but in a backwards-compatible, incrementally-deployable manner.  Perhaps that's something worth discussing at IETF?

 - Jonathan Morton

Re: [Ecn-sane] [Bloat] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

[Wesley Eddy]

Hi, Dave, strangely it looks like nobody has been copying TSVWG on this 
thread, even though that is where the L4S work is happening in the IETF!  :)

I just wanted to respond to one part of your message since I am 
currently acting as document shepherd for the L4S drafts in TSVWG, and 
it seems like maybe you don't know where to find all of the IETF 
materials in order to participate (based on the "stalled out 
indefinitely" comment below).  So in case it's helpful here are some 
pointers to where things are kept.

The 3 base L4S documents were adopted in the TSVWG WG, and have been 
regularly updated.  You can find the charter and milestone dates 
(currently June 2019) quite easily on the WG datatracker page: 
https://datatracker.ietf.org/group/tsvwg/about/ and of course the 
"Documents" tab there takes you to the copies of all the documents.

There have been updates on L4S and presentations/discussions at the IETF 
meetings (with minutes and charts posted to the proceedings), as well as 
L4S draft reviews and comment threads on the TSVWG list whose archives 
are under "List archive".  You can find meeting minutes and slide decks 
also readily linked from that WG page: 
https://datatracker.ietf.org/group/tsvwg/meetings/

There are source code repositories, papers, videos, etc. that the 
proponents have also made very easy to find, e.g. 
https://riteproject.eu/dctth/#code (and as linked in meeting materials).

Since we (TSVWG chairs) are looking for inputs towards WGLC readiness to 
proceed on these, hopefully this information is helpful for you.


On 3/15/2019 6:46 AM, Dave Taht wrote:
 > ...
 >
 > Some background to this: after the L4S/TCP Prague/and dualpi 
experiments appeared stalled out indefinitely in the IETF, and with our 
own frustration with IETF processes, bufferbloat.net project members 
publicly formed our own working group to look into the problems with 
ecn, back in august of last year.