Re: [LOOPS] draft-li-tsvwg-loops-problem-opportunities-05 - How do endpoints understand congestion?
Liyizhou <liyizhou@huawei.com> Thu, 09 July 2020 11:45 UTC
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From: Liyizhou <liyizhou@huawei.com>
To: Gorry Fairhurst <gorry@erg.abdn.ac.uk>, loops <loops@ietf.org>
Thread-Topic: [LOOPS] draft-li-tsvwg-loops-problem-opportunities-05 - How do endpoints understand congestion?
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Date: Thu, 09 Jul 2020 11:45:18 +0000
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Subject: Re: [LOOPS] draft-li-tsvwg-loops-problem-opportunities-05 - How do endpoints understand congestion?
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Hi Gorry, Based on the discussions in the mailing list, we should have removed allusions to being able to detect non-congestion losses from the draft. This github issue was closed about same time as the draft uploading. Hence the draft did not absorb all the conclusions. Sorry about that. Current scope focuses on drop-to-mark approach without trying to detect non-congestion loss. Will update the draft by this week to reflect the most recent consensus (together with those mentioned in your previous email). Rgds, Yizhou -----Original Message----- From: LOOPS [mailto:loops-bounces@ietf.org] On Behalf Of Gorry Fairhurst Sent: Thursday, July 9, 2020 5:58 PM To: loops <loops@ietf.org> Subject: Re: [LOOPS] draft-li-tsvwg-loops-problem-opportunities-05 - How do endpoints understand congestion? Hi, I have questions about congetsion control will be performed. The problem statement says: “LOOPS (Local Optimizations on Path Segments) is a network-assisted performance enhancement over path segment and it aims to provide local in-network recovery to achieve better data delivery by making packet loss recovery faster and by avoiding the senders over-reducing their sending rate. “ [gf] ... which seems interesting. Section 3.3 outlines precisely the problem that “In long-haul links, when the loss is caused by non-persistent burst which is extremely short and pretty random, the sender's reaction of reducing sending rate is not able to respond in time to the instantaneous path situation or to mitigate such bursts. On the contrary, reducing window size at the sender unnecessarily or too aggressively harms the throughput for application's long lasting traffic like bulk data transfer.” [gf] ... Which sounds like it asks questions where I did not find an answer: How does the network segment differentiate between different pathologies that result in loss? I can imagine some random physical layer loss that isn't congestion. I can imagine some random loss that is a result of corruption in a shared media... which may or may not be link-layer congestion? How does the network segment know? So, one reason for asking is I saw these two statements, on informing the end-to-end transport protocol about congestion loss events that distinguish losses: "Existing tools such as ECN will be used." “ A more recent draft, [I-D.ietf-tsvwg-tunnel-congestion-feedback], proposes to activate ECN for the tunnel regardless of whether the end-to-end protocol signals the use of an ECN-capable transport (ECT), which requires more complicated action at the tunnel egress.” [gf] How does this help, please explain? ... The draft mentioned hasn't been changed since Jan 2017, and has not yet captured much experience or comment, so I am quite uneasy about predicting what will finally happen with thart draft. That aside, I'd like to understand how ECN helps in this case, since the congestion-control reaction seems a key part of any LOOPS method. Best wishes, Gorry -- LOOPS mailing list LOOPS@ietf.org https://www.ietf.org/mailman/listinfo/loops
- [LOOPS] draft-li-tsvwg-loops-problem-opportunitie… Gorry Fairhurst
- Re: [LOOPS] draft-li-tsvwg-loops-problem-opportun… Carsten Bormann
- Re: [LOOPS] draft-li-tsvwg-loops-problem-opportun… Gorry Fairhurst
- Re: [LOOPS] draft-li-tsvwg-loops-problem-opportun… Liyizhou
- Re: [LOOPS] draft-li-tsvwg-loops-problem-opportun… Gorry Fairhurst
- Re: [LOOPS] draft-li-tsvwg-loops-problem-opportun… Gorry Fairhurst
- Re: [LOOPS] draft-li-tsvwg-loops-problem-opportun… Michael Welzl
- Re: [LOOPS] draft-li-tsvwg-loops-problem-opportun… Gorry Fairhurst
- Re: [LOOPS] draft-li-tsvwg-loops-problem-opportun… Liyizhou
- Re: [LOOPS] draft-li-tsvwg-loops-problem-opportun… Carsten Bormann
- Re: [LOOPS] draft-li-tsvwg-loops-problem-opportun… Gorry Fairhurst
- Re: [LOOPS] draft-li-tsvwg-loops-problem-opportun… Gorry Fairhurst
- Re: [LOOPS] draft-li-tsvwg-loops-problem-opportun… Carsten Bormann
- Re: [LOOPS] draft-li-tsvwg-loops-problem-opportun… Gorry Fairhurst
- Re: [LOOPS] draft-li-tsvwg-loops-problem-opportun… Carsten Bormann
- Re: [LOOPS] draft-li-tsvwg-loops-problem-opportun… Spencer Dawkins at IETF
- Re: [LOOPS] draft-li-tsvwg-loops-problem-opportun… Carsten Bormann