From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yw1-x1131.google.com (mail-yw1-x1131.google.com [IPv6:2607:f8b0:4864:20::1131]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 5400E3B2A4 for ; Tue, 28 Mar 2023 05:36:13 -0400 (EDT) Received: by mail-yw1-x1131.google.com with SMTP id 00721157ae682-54184571389so218876247b3.4 for ; Tue, 28 Mar 2023 02:36:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; t=1679996172; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=KBruO0YFjmnoOOEl1GhivsgoqNXbhWgGVOjZICOgIR8=; b=mC84GQiKjxwmnNZweQM39nza406LWgdSJ3KAd0+J+sd624X1vNE5Y8kak3Xr2KnSPo xEYtKbxldct4i1/DrXtt6AAkkdSIAwcceT8lI0Bpnuu0+Y0fj6dvNCGKy/4s67xWRe3Q SK2kt13aUGjPb3PqdMyuPq2f2c5aYe+ek4S9Tr0k7kvx+8uTj1mx8WN45ub2H4NxTCnz eyueXVK18QMN4RQu20flW2yyTuPxPY/xWkI8hYQ1d54XuC5+2eWFxKxBt86YVcMQOzT0 kQwVdkYtg1y9qZ2v/9mWj94DSlvVAS4HIo/GtgXUEX/VUGbrFeNHqAk9PYNBpvloO35O QCtg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1679996172; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=KBruO0YFjmnoOOEl1GhivsgoqNXbhWgGVOjZICOgIR8=; b=XbFgTcKaBxMAn6eCFlq0PhjnBAXncjyknTIFWg4HRfp345PfMTJOr9mnoggwOp4STQ KpE/r9wDzzwpR9wlo5y/b42o2ZmIK2/lsRh4G3NbTLwF7eRjell9DaSgs221aEjCz9Gk lWn1dCBOvGmZqa6YaFZrsE5496JgQhz8tX8JQJPwqAs9MCpmSBSgRje7ALyul+/UBvlr VbzVScFAr4K6HTKaSVH4KAK2BTR2NE7N8+LphKyj/uFqy8PHhEfwc3zUTapZrjRWVSz6 Cejo7dLvTUHPkmXO+nhETIyuEWtLwDInxnfAFNPoYOLOJNUPbWtlCpTujNnyqxob5Ok1 LtgQ== X-Gm-Message-State: AAQBX9fhUsE5gUajvgXABBM/M3yV5rkHD0VISNAhMfOBv69QFDkbDvUc U82Qv7zD83UaFK93HfraY7wpjocTrAwBKLRtIpU= X-Google-Smtp-Source: AKy350butDKCw+QH2eGusv9N8PUTGblZ7aUa5Y+ldvdNiZlAInxaSa5ErWlnwnmWbzj0N8qRDLUdTqxxq734V8RpNAc= X-Received: by 2002:a81:ae23:0:b0:53c:6fda:835f with SMTP id m35-20020a81ae23000000b0053c6fda835fmr6741074ywh.0.1679996172616; Tue, 28 Mar 2023 02:36:12 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Ayush Mishra Date: Tue, 28 Mar 2023 17:36:01 +0800 Message-ID: To: Neal Cardwell Cc: Dave Taht , bloat , BBR Development , ayush@comp.nus.edu.sg Content-Type: multipart/alternative; boundary="00000000000017c79705f7f297b6" X-Mailman-Approved-At: Tue, 28 Mar 2023 06:45:39 -0400 Subject: Re: [Bloat] [bbr-dev] Re: Are we heading towards a BBR-dominant Internet? X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 28 Mar 2023 09:36:13 -0000 --00000000000017c79705f7f297b6 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hey Neal, I was revisiting this thread before presenting this paper in iccrg tomorrow - and I was particularly intrigued by one of the motivations you mentioned for BBR: "BBR is not trying to maintain a higher throughput than CUBIC in these kinds of scenarios with steady-state bulk flows. BBR is trying to be robust to the kinds of random packet loss that happen in the real world when there are flows dynamically entering/leaving a bottleneck." BBRv1 essentially tried to deal with this problem by doing away with packet loss as a congestion signal and having an entirely different philosophy to congestion control. However, if we set aside the issue of buffer bloat, I would imagine packet loss is a bad congestion signal in this situation because most loss-based congestion control algorithms use it as a binary signal with a binary response (back-off or no back-off). In other words, I feel the blame must be placed on not just the congestion signal, but also on how most algorithms respond to this congestion signal. On a per-packet basis, packet loss is a binary signal. But over a window, the loss percentage and distribution, for example, can be a rich signal. There is probably scope for differentiating between different kinds of packet losses (and deciding how to react to them) when packet loss is coupled with the most recent delay measurement too. Now that BBRv2 reacts to packet loss, are you making any of these considerations too? This is not something I plan to present in iccrg tomorrow, just something I was curious about :) Warmest regards, Ayush On Fri, Aug 26, 2022 at 9:36=E2=80=AFPM 'Neal Cardwell' via BBR Development= < bbr-dev@googlegroups.com> wrote: > Yes, I agree the assumptions are key here. One key aspect of this paper i= s > that it focuses on the steady-state behavior of bulk flows. > > Once you allow for short flows (like web pages, RPCs, etc) to dynamically > enter and leave a bottleneck, the considerations become different. As is > well-known, Reno/CUBIC will starve themselves if new flows enter and caus= e > loss too frequently. For CUBIC, for a somewhat typical 30ms broadband pat= h > with a flow fair share of 25 Mbit/sec, if new flows enter and cause loss > more frequently than roughly every 2 seconds then CUBIC will not be able = to > utilize its fair share. For a high-speed WAN path, with 100ms RTT and fai= r > share of 10 Gbit/sec, if new flows enter and cause loss more frequently > than roughly every 40 seconds then CUBIC will not be able to utilize its > fair share. Basically, loss-based CC can starve itself in some > very typical kinds of dynamic scenarios that happen in the real world. > > BBR is not trying to maintain a higher throughput than CUBIC in these > kinds of scenarios with steady-state bulk flows. BBR is trying to be robu= st > to the kinds of random packet loss that happen in the real world when the= re > are flows dynamically entering/leaving a bottleneck. > > cheers, > neal > > > > > On Thu, Aug 25, 2022 at 8:01 PM Dave Taht via Bloat < > bloat@lists.bufferbloat.net> wrote: > >> I rather enjoyed this one. I can't help but wonder what would happen >> if we plugged some different assumptions into their model. >> >> https://www.comp.nus.edu.sg/~bleong/publications/imc2022-nash.pdf >> >> -- >> FQ World Domination pending: >> https://blog.cerowrt.org/post/state_of_fq_codel/ >> Dave T=C3=A4ht CEO, TekLibre, LLC >> _______________________________________________ >> Bloat mailing list >> Bloat@lists.bufferbloat.net >> https://lists.bufferbloat.net/listinfo/bloat >> > -- > You received this message because you are subscribed to the Google Groups > "BBR Development" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to bbr-dev+unsubscribe@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/bbr-dev/CADVnQykKbnxpNcpuZATug_4VLhV1%3= DaoTTQE2263o8HF9ye_TQg%40mail.gmail.com > > . > --00000000000017c79705f7f297b6 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Hey Neal,

I was revisiting t= his thread before presenting this paper in iccrg tomorrow - and I was parti= cularly intrigued by one of the motivations you mentioned for BBR:

"BBR is not trying to maintain a higher = throughput than CUBIC in these kinds of scenarios with steady-state bulk fl= ows. BBR is trying to be robust to the kinds of random packet loss that happen=20 in the real world when there are flows dynamically entering/leaving a=20 bottleneck."

BBRv1 essentially tried to deal = with this problem by doing away with packet loss as a congestion signal and= having an entirely different philosophy to congestion control. However, if= we set aside the issue of buffer bloat, I would imagine packet loss is a b= ad congestion signal in this situation because most loss-based congestion c= ontrol algorithms use it as a binary signal with a binary response (back-of= f or no back-off). In other words, I feel the blame must be placed on not j= ust the congestion signal, but also on how most algorithms respond to this = congestion signal.

On a per-packet basis, pac= ket loss is a binary signal. But over a window, the loss percentage and dis= tribution, for example, can be a rich signal. There is probably scope for d= ifferentiating between different kinds of packet losses (and deciding how t= o react to them) when packet loss is coupled with the most recent delay mea= surement too. Now that BBRv2 reacts to packet loss, are you making any of t= hese considerations too?

This is not somethin= g I plan to present in iccrg tomorrow, just something I was curious about := )

Warmest regards,
Ayush
=
On Fri= , Aug 26, 2022 at 9:36=E2=80=AFPM 'Neal Cardwell' via BBR Developme= nt <bbr-de= v@googlegroups.com> wrote:
Yes, I agree the assumptions are key her= e. One key aspect of this paper is that it focuses on the steady-state beha= vior of bulk flows.

Once you allow for short flows (like= web pages, RPCs, etc) to dynamically enter and leave a bottleneck, the con= siderations become different. As is well-known, Reno/CUBIC will starve them= selves if new flows enter and cause loss too frequently. For CUBIC, for a s= omewhat typical 30ms broadband path with a flow fair share of 25 Mbit/sec, = if new flows enter and cause loss more frequently than roughly every 2 seco= nds then CUBIC will not be able to utilize its fair share. For a high-speed= WAN path, with 100ms RTT and fair share of 10 Gbit/sec,=C2=A0 if new flows= enter and cause loss more frequently than roughly every 40 seconds then CU= BIC will not be able to utilize its fair share. Basically, loss-based CC ca= n starve itself in some very=C2=A0typical=C2=A0kinds of dynamic scenarios t= hat happen in the real world.

BBR is not trying to= maintain a higher throughput than CUBIC in these kinds of scenarios with s= teady-state bulk flows. BBR is trying to be robust to the kinds of random p= acket loss that happen in the real world when there are flows dynamically e= ntering/leaving a bottleneck.

cheers,
ne= al




On Thu, Aug 25, 2022= at 8:01 PM Dave Taht via Bloat <bloat@lists.bufferbloat.net> wrote:
I rather enjoyed this = one. I can't help but wonder what would happen
if we plugged some different assumptions into their model.

https://www.comp.nus.edu.sg/~bleong= /publications/imc2022-nash.pdf

--
FQ World Domination pending: https://blog.cerowrt.or= g/post/state_of_fq_codel/
Dave T=C3=A4ht CEO, TekLibre, LLC
_______________________________________________
Bloat mailing list
Bloat@list= s.bufferbloat.net
https://lists.bufferbloat.net/listinfo/bloat

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