Re: [Bloat] buffer sizing meeting notes
On Sat, Aug 24, 2019 at 9:59 AM Sebastian Moeller wrote: > Another nugget from the notes ( > http://yuba.stanford.edu/~bspang/buffer-sizing-meeting/notes/): > > This looks like an argument for fq_codel/cake's use of time instead of > queue length, OR an argument for fq, because in a non-overwhelmed fq_system > the local bucket's queue length should be somewhat stronger correlated with > the sojurn times, than the sojurn time of a packet though a shared queue, > no? > I believe that using fq there are good implications in terms of buffer sizing rules. The focus is only on backlogged flows. The sparse flow queue can be sized purely based on queue load. Which is trivial queuing theory formulas with non-TCP traffic. For backlogged flows, sizing is just like sizing a buffer for a single TCP flow. So the computation can be done based on estimations of the number of backlogged flows and by setting the cut-off BDP based on the largest (maximum) min RTT one want to serve optimally. So AQM is really needed to get optimality. The number of backlogged flows could be estimated as a max value or an avg value, and this of course changes depending on the network segment (DC, residential, campus, access, backhaul etc.). Nick McKeown has done quite a lot of research on the topic (reported in the slide deck), so I find hilarious the following in his slide deck "Personal confession: I have no idea what the general answer is" about sizing buffers! ___ Bloat mailing list Bloat@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/bloat
Re: [Bloat] buffer sizing meeting notes
Another nugget from the notes (http://yuba.stanford.edu/~bspang/buffer-sizing-meeting/notes/): Chuanxiong Guo, Bytedance Talked about buffering in Bytedance’s datacenters. The top of rack switches have buffers of 12-32MB, and the aggregation switches have larger buffers of several GB. Were hoping to use ECN to reduce buffers for aggregation switches, but argued that precise ECN marking on egress queue length in VoQs is hard. However, Arista and Barefoot said they’ve fixed this using the packet latency instead of queue length for ECN. This looks like an argument for fq_codel/cake's use of time instead of queue length, OR an argument for fq, because in a non-overwhelmed fq_system the local bucket's queue length should be somewhat stronger correlated with the sojurn times, than the sojurn time of a packet though a shared queue, no? Best Regards Sebastian > On Aug 24, 2019, at 09:54, Jesper Dangaard Brouer wrote: > > On Fri, 23 Aug 2019 10:13:39 -0700 > Simon Barber wrote: > >>> On Aug 23, 2019, at 9:07 AM, Dave Taht wrote: >>> >>> There's some good preso from various representatives in the dc market here. >>> >>> The p4 stuff, in particular (from barefoot) is looking impressive. >>> >>> http://yuba.stanford.edu/~bspang/buffer-sizing-meeting/ > > I followed the link to the animation of AIMD (Additive > Increase/Multiplicative Decrease), that was really cool! > > https://dabh.github.io/network_animations/ > > -- > Best regards, > Jesper Dangaard Brouer > MSc.CS, Principal Kernel Engineer at Red Hat > LinkedIn: http://www.linkedin.com/in/brouer > ___ > 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: [Bloat] buffer sizing meeting notes
On Fri, 23 Aug 2019 10:13:39 -0700 Simon Barber wrote: > > On Aug 23, 2019, at 9:07 AM, Dave Taht wrote: > > > > There's some good preso from various representatives in the dc market here. > > > > The p4 stuff, in particular (from barefoot) is looking impressive. > > > > http://yuba.stanford.edu/~bspang/buffer-sizing-meeting/ I followed the link to the animation of AIMD (Additive Increase/Multiplicative Decrease), that was really cool! https://dabh.github.io/network_animations/ -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer ___ Bloat mailing list Bloat@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/bloat
Re: [Bloat] buffer sizing meeting notes
Simon Barber writes: > The Netflix presentation requires a password - can you share it? I was not at this meeting, I just stumbled across the url. I don't even know how, I think I was looking for the old (and good!) stanford buffersizing paper, and there was this set of updates from various parties on the current state of some hardware. > > Simon > > >> On Aug 23, 2019, at 9:07 AM, Dave Taht wrote: >> >> There's some good preso from various representatives in the dc >> market here. >> >> The p4 stuff, in particular (from barefoot) is looking impressive. >> >> http://yuba.stanford.edu/~bspang/buffer-sizing-meeting/ >> >> >> -- >> >> 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 > > ___ > 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: [Bloat] buffer sizing meeting notes
The Netflix presentation requires a password - can you share it? Simon > On Aug 23, 2019, at 9:07 AM, Dave Taht wrote: > > There's some good preso from various representatives in the dc market here. > > The p4 stuff, in particular (from barefoot) is looking impressive. > > http://yuba.stanford.edu/~bspang/buffer-sizing-meeting/ > > > -- > > 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 ___ Bloat mailing list Bloat@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/bloat
[Bloat] buffer sizing meeting notes
There's some good preso from various representatives in the dc market here. The p4 stuff, in particular (from barefoot) is looking impressive. http://yuba.stanford.edu/~bspang/buffer-sizing-meeting/ -- 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
