[Cerowrt-devel] Bufferbloat at upcoming LUG talk

Jim Gettys jg at freedesktop.org
Mon Nov 26 10:37:11 EST 2012 

On Mon, Nov 26, 2012 at 6:49 AM, Dave Taht <dave.taht at gmail.com> wrote:

> All of Jims presos are licences under one of the creative commons licenses.
>
> Mine would be, too, if I had bothered to mark them as such. I will go
> back and correct this. Feel free to reuse whatever you like, with the
> caveat that all these presos do reflect enhanced thinking and research
> over time, and sometimes contain errors or ideas that have been
> revised.
>
> Original libreoffice and powerpoint sources for jim's stuff are at
> http://mirrors.bufferbloat.net/


Me bad; I haven't uploaded more recent versions of my talks.  I'll add it
to my "todo list", to do RSN...
                                - Jim


>
> Mine are mostly at: http://www.teklibre.com/~d/bloat/Talks/
>
> - the
> linuxcon talk is not up in source form because I wanted to illustrate
> several of the graphs better.
>
>
>
> On Mon, Nov 26, 2012 at 2:11 AM, Richard Brown
> <richard.e.brown at dartware.com> wrote:
> > Folks,
> >
> > I am planning to give a talk about Bufferbloat to the local Linux User
> Group next week (http://dlslug.org
>
> ). All this traffic on the list is fantastic, because it gives me a lot of
> background on the current state of bufferbloat. I've pulled together a
> bunch of general questions about CeroWrt that I would like to be able to
> cover if they come up:
> >
> > - Is it true that the latest CeroWrt is Sugarland 3.3.8-26 from
> mid-September? (My router is using this build - r33460.)
>
> Yes. A lot of updates have accumulated, I do hope to get a new release
> out soon and start up 3.6.x+ development. I'm extremely encouraged by
> what is in 3.6 and later.
>
> I note there is a nasty hole in the sugarland config that new users
> should close immediately on a new install.
>
> http://www.bufferbloat.net/issues/411
>
>
>
> > - I see the "QoS" item in the Network tab of the web GUI. Is this
> important for Sugarland? Or does some other router configuration take care
> of this now?
>
> Openwrt QoS works ok on ipv4 traffic. (yes, it uses fq_codel). However
> the simple_qos.sh script I have been prototyping works on everything
> and seems to be mildly better. In part that's due to handling ipv6
> traffic correctly, and possibly due to the fact it has "nfq_codel" in
> it, rather than fq_codel, which is a respin of fq_codel using the
> latest ns2 model of codel behind it, which differs in some important
> respects.
>
> It was obvious after working on that that better benchmarks were
> needed, which has been a focus these past 2 months.
>
> simple_qos.sh does require manual configuration, however, and testing
> for an accurate bandwidth estimate is problematic even with the rrul
> test. I would really like someone to make this available via a gui,
> and more people to beat on it...
>
> (and I'll rename this ceroshaper in the next release)
>
> And: I would prefer to stress to all audiences that this stuff is WIP,
> and try to get them to understand that the goal is to do smart
> queueing over top the smallest possible amount of buffering, and a
> multitude of factors can lead to sub-optimal results.
>
> rather than "install this script on your random hardware, expect
> magic". Or: "Download this firmware, expect magic".
>
> As one example, I was completely blindsided the other day, when
> working with david woodhouse, by the new GRO network offload
> "feature", on his device, which wedges enormous packets into the
> stack. That needs to get turned off on linux based routers, generally.
> Somehow. Preferably, automatically.
>
> (I am delighted that multiple ADSL folk, including david, just made a
> huge dent in adsl latencies over on the netdev mailing list)
>
> > - What's the relationship between the QoS GUI item above and the
> debloat.sh and simple_qos.sh scripts that have been mentioned on this list?
> What's the best practice here for getting a router up and running?
>
> the debloat (written in lua) script in the ceropackages repository
> makes sure that various latency inducing network offloads (on by
> default in linux) are OFF. I recently learned that the GRO offload
> could induce a problem, I don't remember if that's off in sugarland.
> It runs on ALL interfaces by default in cerowrt....
>
> People trying to make debloating a router work on other platforms than
> cerowrt, should modify that script to run on all their interfaces.
> Or...
>
> debloat.sh is a simpler version of debloat that doesn't do all the
> stuff debloat does, yet, but works on debian/ubuntu. It needs to be
> better, turning off gro for example on ALL devices, and I like that it
> lacks the lua dependency.
>
> I incidentally note that I no longer remember what's in sugarland for
> simple_qos and debloat, what I am fiddling with now is not checked in.
> I think a difference is that I'm using a different quantum, am only
> using ecn on ingress.
>
> >
> > - I can see how the CeroWrt de-bloating algorithms help protect against
> bad latency when I'm *uploading* big files. I'm not sure whether using
> CeroWrt with its CoDel/FQ/SFQ/etc. helps when I'm downloading big files,
> though. What can I say about this?
>
> Most shapers in the world try hard to address ingress and egress. It
> is very byzantine to configure the default ingress shaper "IFB", but
> that's what is done.
>
> Shaping ingress traffic has been one of the few places where I have
> seen ECN give a benefit. ECN on egress, seems to be a lose at most
> bandwidths I've tried.
>
> The right place for ingress shaping, however, really is at the head
> end or dslam.
>
>
> >
> > - I believe the default DNS server in Sugarland is dnsmasq,
>
> Bind ate way too much memory. Writing a gui for it proved nearly
> impossible. Dnsmasq has evolved over the past year to include a nifty
> AAAA and dhcpv6 naming scheme (and added dhcpv6, and has nearly enough
> functionality to replace the radvd daemon now). I'm very happy with
> the directions dnsmasq is going.
>
> (I'd really like to get some help on getting AHCP into it)
>
> > not bind. Is DNSSEC enabled by default?
>
> DNSSEC is temporarily gone.
>
> Simon kelly of dnsmasq is making some progress towards making it fit
> into dnsmasq. As he lacks time and resources on his side, I can't give
> an estimate as to arrival time, but I'm sure it will be a lot more
> tiny and more web configurable, whenever it's done. There's partial
> DNSSEC support in a branch of dnsmasq, patches would be welcomed....
>
> I learned this week that dnsmasq is the default dns/dhcp server in
> android, for tethering, and is also heavily used in libvirt and
> various clustering solutions. That's in addition to near dominance of
> the linux based home router market...
>
> And for all that market penetration, (at least 1/4 of the internet)
> simon and his crew have made such solid software, in their spare time,
> as for nobody to know who they are. It's sad, and frustrating...
>
> I admit that I like a few features of bind, such as views, and
> nsupdate... Bind can be optionally installed via installing
> bind-latest and bind-latest-config via opkg.
> I certainly plan to leave bind available for those that want it, but
> going forward,
> unless MBs of ram drop from the sky for free for everyone, it's not going
> to be
> the default in cerowrt.
>
> > Also: there's a report (Bug #411) that says that DNS is leaking internal
> names to the outside world. What's the best advice for closing this? ("list
> notinterface 'ge00'" is one recommendation…)
>
> yes. EVERYBODY please do that.
>
> >
> > - I've been assembling information about the various de-bloating
> techniques implemented in CeroWrt. It seems that Infoblox has recently
> reorganized their blogs, and the links published earlier this week have all
> broken. Here are updates:
> >
> >
> http://www.infoblox.com/community/blog/application-analysis-using-tcp-retransmissions-part-1
>
>
> >
> http://www.infoblox.com/community/blog/application-analysis-using-tcp-retransmissions-part-2
>
>
> > http://www.infoblox.com/community/blog/router-buffer-tuning
>
>
> >
> http://www.infoblox.com/community/blog/rethinking-interface-error-reports
>
>
>
> Thx.
>
> > My plan is to give a little of the science behind bufferbloat mitigation
> and also put in a plug for CeroWrt. Any topics I haven't already mentioned
> that I should? Thanks!
> >
> > Rich Brown
> > Hanover, NH USA
> > _______________________________________________
> > Cerowrt-devel mailing list
> > Cerowrt-devel at lists.bufferbloat.net
> > https://lists.bufferbloat.net/listinfo/cerowrt-devel
>
>
>
>
>
> --
> Dave Täht
>
> Fixing bufferbloat with cerowrt:
> http://www.teklibre.com/cerowrt/subscribe.html
>
>
> _______________________________________________
> Cerowrt-devel mailing list
> Cerowrt-devel at lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/cerowrt-devel
>
>
>
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