[Cerowrt-devel] [Bloat] fq_codel is two years old

David Lang david at lang.hm
Thu May 15 20:23:36 PDT 2014 

Well, if the link isn't congested, why do you need to do anything to the traffic 
other than forward it? You have no way of knowing what paths the traffic is 
going to follow once it hits the next router, so you don't know which streams 
are independent of each other.

Now, if you are saying that fq_codel can be enhanced to gather stats even when 
there is no congestion so that it has a better idea of what to do once 
congestion starts, then you may have a point.

but fq_codel is very happy to run and do basically nothing if there is no 
congestion. It doesn't delay things to create a buffer.

David Lang

  On Thu, 15 May 2014, David P. Reed wrote:

> Both you and Dave Taft misunderstood my idea about standing queues not being the right way to encode congestion in switches. I do not say there would be no buffers for jitter. Nor do I call for admission control. I just suggest that instead of deriving congestion from backlog measures (requiring that there be backlogs created and sustained) one can derive congestion measures without sustainng a backlog...
>
> The result is ballistic flows, if you will. Analogous to ballistic electrons in materials.
>
> On May 15, 2014, David Lang <david at lang.hm> wrote:
>> We are talking about different things then.
>>
>> The "fast lane" I'm talking about is where ISPs want companies to pay
>> them for
>> bandwidth (in addition to the companies paying their own ISP for
>> bandwidth and
>> in addition to their users paying them for bandwidth)
>>
>> As for your contention that an ideal Internet will have a buffer size
>> of <1
>> packet. That will work, but that will not fully utilize the network,
>> because
>> there will be jitter in the senders and some packet generation will be
>> delayed,
>> leaving the network with nothing to send in that timeslot.
>>
>> If the network is not fully utilized, then fq_codel isn't needed, just
>> send
>> packets as they arrive. It's only as a particular link approaches full
>> utilization that queues will build up and deciding what to do becomes
>> significant (and fq_codel and similar will matter)
>>
>> As for your thought of having an end-to-end feedback loop, the problem
>> with that
>> is that it will only work if the path between them is stable and not
>> interfered
>> with by other flows. In the Internet as we have it today, neither are
>> true. The
>> packets for your connection may travel over different paths, and
>> congestion
>> happens on a link-by-link basis with the combined packets of many
>> connections,
>> not end-to-end based on a single connection.
>>
>> David Lang
>>
>> On Thu, 15 May 2014, dpreed at reed.com wrote:
>>
>>> I don't think that at all. I suspect you know that. But if I confused
>> you, let
>>> me assure you that my view of the proper operating point of the
>> Internet as a
>>> whole is that the expected buffer queue on any switch anywhere in the
>> Internet
>>> is < 1 datagram.
>>>
>>> fq_codel is a good start, but it still requires letting buffer
>> queueing
>>> increase.  However, mathematically, one need not have the queues
>> build up to
>>> sustain the control loop that fq_codel creates.
>>>
>>> I conjecture that one can create an equally effective congestion
>> control
>>> mechanism as fq_codel without any standing queues being allowed to
>> build up.
>>> (Someone should try the exercise of trying to prove that an optimal
>> end-to-end
>>> feedback control system requires queueing delay to be imposed. I've
>> tried and
>>> it's led me to the conjecture that one can always replace a standing
>> queue
>>> with a finite memory of past activities - and if one does, the lack
>> of a
>>> standing queue means that the algorithm is better than any that end
>> up with a
>>> standing queue).
>>>
>>> fq_codel could be redesigned into a queue-free fq_codel.
>>>
>>>
>>> On Thursday, May 15, 2014 7:46pm, "David Lang" <david at lang.hm> said:
>>>
>>>
>>>
>>>> If you think "fast lanes" will actually increase performance for any
>> traffic,
>>>> you are dreaming.
>>>>
>>>> the people looking for "fast lanes" are't trying to get traffic
>> through any
>>>> faster, they are looking to charge more for the traffic they are
>> already
>>>> passing.
>>>>
>>>> David Lang
>>>>
>>>>   On Thu, 15 May 2014, dpreed at reed.com wrote:
>>>>
>>>>> Well done.  I'm optimistic for deployment everywhere, except
>> CMTS's, the LTE
>>>> and HSPA+ access networks, and all corporate firewall and intranet
>> gear.
>>>>>
>>>>> The solution du jour is to leave bufferbloat in place, while using
>> the real
>>>> fads: prioritization (diffserv once we have the "fast lanes" fully
>> legal) and
>>>> "software defined networking" appliances that use DPI for packet
>> routing and
>>>> traffic management.
>>>>>
>>>>> Fixing buffer bloat allows the edge- and enterprise- networks to
>> be more
>>>> efficient, whereas not fixing it lets the edge networks move users
>> up to more and
>>>> more expensive "plans" due to frustration and to sell much more gear
>> into
>>>> Enterprises because they are easy marks for complex gadgets.
>>>>>
>>>>> But maybe a few engineers who operate and design gear for such
>> networks will
>>>> overcome the incredible business biases against fixing this.
>>>>>
>>>>> That's why all the efforts you guys have put forth are immensely
>> worth it.  I
>>>> think this is one of the best innovations in recent years (Bram
>> Cohen's original
>>>> BitTorrent is another, for fully decentralizing data delivery for
>> the very first
>>>> time in a brilliant way.) I will certainly push everywhere I can to
>> see fq_codel
>>>> deployed.
>>>>>
>>>>> If there were a prize for brilliant projects, this would be top on
>> my list.
>>>>>
>>>>>
>>>>>
>>>>> On Wednesday, May 14, 2014 9:25pm, "Dave Taht"
>> <dave.taht at gmail.com>
>>>> said:
>>>>>
>>>>>
>>>>>
>>>>>> On Wed, May 14, 2014 at 3:32 PM, Kathleen Nichols
>>>> <nichols at pollere.com>
>>>>>> wrote:
>>>>>>>
>>>>>>> Thanks, Rich.
>>>>>>>
>>>>>>> And to show you what an amazing bit of work that first fq_codel
>> was,
>>>> I have
>>>>>>> on my calendar that I first "exposed" CoDel to a small group in
>> a
>>>>>>> meeting room
>>>>>>> and on the phone at ISC on April 24.
>>>>>>
>>>>>> And we had all sorts of trouble with the phone, (eric didn't hear
>>>>>> much) and we then spent hours and hours afterwards discussing
>> wifi
>>>>>> instead of codel... it was too much to take in...
>>>>>>
>>>>>> me, I'd started jumping up and down in excitement about 20
>> minutes
>>>>>> into kathies preso...
>>>>>>
>>>>>> May 3rd, 2012 was the last 24 hr coding stint I think I'll ever
>> have.
>>>>>>
>>>>>>
>> https://lists.bufferbloat.net/pipermail/codel/2012-May/000023.html
>>>>>>
>>>>>> Ahh, the good ole days, when bufferbloat was first solved and we
>> all
>>>>>> thought the internet would speed up overnight, and we were going
>> to be
>>>>>> rock stars, invited to all the best parties, acquire fame and
>> fortune,
>>>>>> and be awarded medals and given awards. Re-reading all this
>> brought
>>>>>> back memories.... (heck, there's still a couple good ideas in
>> that
>>>>>> thread left unimplemented)
>>>>>>
>>>>>>
>> https://lists.bufferbloat.net/pipermail/codel/2012-May/thread.html
>>>>>>
>>>>>> It looks by may 5th we were getting in shape, and then there were
>> a
>>>>>> few other issues along the way with the control law and so on...
>> and
>>>>>> eric rewrote the whole thing and made it oodles faster and then
>> as
>>>>>> best as I recall came up with fq_codel on saturday may 5th(?) -
>>>>>>
>>>>>> Ah, I haven't had so much fun in in years. My life since then
>> seems
>>>>>> like an endless string of meetings, politics, and bugfixing.
>>>>>>
>>>>>> The code went from sim/paper, to code, to testing, to mainline
>> linux
>>>>>> in another week. I wish more research went like that!
>>>>>>
>>>>>> commit 76e3cc126bb223013a6b9a0e2a51238d1ef2e409
>>>>>> Author: Eric Dumazet <edumazet at google.com>
>>>>>> Date:   Thu May 10 07:51:25 2012 +0000
>>>>>>
>>>>>>     codel: Controlled Delay AQM
>>>>>>
>>>>>> Now, as I recall the story, eric came up with fq_codel on a
>> saturday
>>>>>> afternoon, so I guess that was may 5th - cinco de mayo!
>>>>>>
>>>>>> And that too, landed in mainline...
>>>>>>
>>>>>> commit 4b549a2ef4bef9965d97cbd992ba67930cd3e0fe
>>>>>> Author: Eric Dumazet <edumazet at google.com>
>>>>>> Date:   Fri May 11 09:30:50 2012 +0000
>>>>>>
>>>>>>     fq_codel: Fair Queue Codel AQM
>>>>>>
>>>>>> let's not forget tom herbert & BQL
>>>>>>
>>>>>> commit 75957ba36c05b979701e9ec64b37819adc12f830
>>>>>> Author: Tom Herbert <therbert at google.com>
>>>>>> Date:   Mon Nov 28 16:32:35 2011 +0000
>>>>>>
>>>>>>     dql: Dynamic queue limits
>>>>>>
>>>>>>     Implementation of dynamic queue limits (dql).  This is a
>> libary
>>>> which
>>>>>>     allows a queue limit to be dynamically managed.  The goal of
>> dql is
>>>>>>     to set the queue limit, number of objects to the queue, to be
>>>> minimized
>>>>>>     without allowing the queue to be starved.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>> It was really amazing to me to watch
>>>>>>> something Van and I had been discussing (okay, arguing) about
>>>> privately for
>>>>>>> 6 months and I'd been tinkering with be turned into real code
>> on
>>>> real
>>>>>>> networks.
>>>>>>> Jim Gettys is an incredible (and constructive) nagger, Eric
>> Dumazet
>>>> and
>>>>>>> amazing
>>>>>>> coder, and the entire open source community a really nifty
>> group of
>>>> folks.
>>>>>>>
>>>>>>> Maybe someday we will actually update the first article with
>> some of
>>>> the
>>>>>>> stuff
>>>>>>> we got into the last internet draft....
>>>>>>>
>>>>>>>         be the change,
>>>>>>>                 Kathie
>>>>>>>
>>>>>>> On 5/14/14 2:01 PM, Rich Brown wrote:
>>>>>>>> Folks,
>>>>>>>>
>>>>>>>> I just noticed that the announcement for the first testable
>>>>>>>> implementation of fq_codel was two days ago today - 14 May
>>>> 2012.
>>>>>>>> Build 3.3.6-2 was the first to include working fq_codel.
>>>>>>>>
>>>>>>
>>>>
>> https://lists.bufferbloat.net/pipermail/cerowrt-devel/2012-May/000233.html
>>>>>>>>
>>>>>>>>  Two years later, we see fq_codel being adopted lots of
>> places.
>>>> As
>>>>>>>> more and more people/organizations come to understand the
>>>> problem,
>>>>>>>> and how straightforward the solution can be, we're beginning
>> to
>>>> win
>>>>>>>> the battle to have a good Internet experience everywhere.
>>>>>>>>
>>>>>>>> Thanks to Dave, Eric, Kathie, Van, and all the members of this
>>>> list
>>>>>>>> for their perseverance, testing, comments, and patience.
>>>>>>>> Congratulations!
>>>>>>>>
>>>>>>>> Best regards,
>>>>>>>>
>>>>>>>> Rich _______________________________________________ Bloat
>>>> mailing
>>>>>>>> list Bloat at lists.bufferbloat.net
>>>>>>>> https://lists.bufferbloat.net/listinfo/bloat
>>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> Bloat mailing list
>>>>>>> Bloat at lists.bufferbloat.net
>>>>>>> https://lists.bufferbloat.net/listinfo/bloat
>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Dave Täht
>>>>>>
>>>>>> NSFW:
>>>>>>
>>>>
>> https://w2.eff.org/Censorship/Internet_censorship_bills/russell_0296_indecent.article
>>>>>> _______________________________________________
>>>>>> Cerowrt-devel mailing list
>>>>>> Cerowrt-devel at lists.bufferbloat.net
>>>>>> https://lists.bufferbloat.net/listinfo/cerowrt-devel
>>>>>> _______________________________________________
>>>> Bloat mailing list
>>>> Bloat at lists.bufferbloat.net
>>>> https://lists.bufferbloat.net/listinfo/bloat
>>>>
>
> -- Sent from my Android device with K-@ Mail. Please excuse my brevity.

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