[aqm] draft-khademi-alternativebackoff - lightly loaded, high BDP paths
Simon Barber <simon@superduper.net> Tue, 13 October 2015 03:09 UTC
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Date: Mon, 12 Oct 2015 20:09:07 -0700
From: Simon Barber <simon@superduper.net>
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Subject: [aqm] draft-khademi-alternativebackoff - lightly loaded, high BDP paths
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I was very interested to see this draft discusses a problem with AQMs AQM schemes like CoDel and PIE use congestion notifications to constrain the queuing delays experienced by packets, rather than in response to impending or actual bottleneck buffer exhaustion. With current default delay targets, CoDel and PIE both effectively emulate a shallow buffered bottleneck (section II, [ABE2015 <https://tools.ietf.org/html/draft-khademi-alternativebackoff-ecn-01#ref-ABE2015>]). This interacts acceptably for TCP connections over low BDP paths, or highly multiplexed scenarios (lmany concurrent TCP connections). However, it interacts badly with lightly-multiplexed cases (few concurrent connections) over high BDP paths. Conventional TCP backoff in such cases leads to gaps in packet transmission and underutilisation of the path. I think it wold be good to add some discussion of this effect to the draft on evaluating AQM algorithms. In many access network scenarios the paths will be lightly loaded, and sometimes higher BDPs will be experienced. In these cases it's good to know that the AQM is not hurting your experience. Simon
- [aqm] draft-khademi-alternativebackoff - lightly … Simon Barber
- Re: [aqm] draft-khademi-alternativebackoff - ligh… Naeem Khademi