[Tmrg] Now, where were we...?
dunn at umn.edu (Larry Dunn) Thu, 19 November 2009 12:44 UTC
From: "dunn at umn.edu"
Date: Thu, 19 Nov 2009 06:44:40 -0600
Subject: [Tmrg] Now, where were we...?
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References: <aa7d2c6d0911181647i755ed6eft9dbe3168d38019b3@mail.gmail.com>
Message-ID: <B7F5500F-02D4-4F75-AAE2-2D654AD9891D@umn.edu>
Lachlan, I'll self-declare as group "A" - though you wouldn't conclude that from my level of contribution to the list, lately. ;-) Nice set of issues- I'll start re-pondering them (and hope others think/reply more quickly than me on said issues...) Larry -- On Nov 18, 2009, at 6:47 PM, Lachlan Andrew wrote: > Greetings all, > > Things have been rather quiet on this list since Sally's retirement, > and I'd like to get things moving again (after Aaron's gentle > prompting :) > > Just as a stock-take, could people please indicate whether they > consider themselves > A: part of the TMRG > B: subscribed to this list to follow "what they in the TMRG are > doing" > Since this WG was chartered as "mailing-list only", everyone on the > list is really in group A, whether they know it or not. > > For those who prefer publishing papers than writing Internet Drafts, > remember that the licence for an ID allows "derivative works", so you > can still publish your models/evaluation/... Like the ArXiv, the ID > process is a good way to place a stamp on your ideas and get feedback > before publishing. > > > > What important open issues issues are there in transport modelling? > (Rather than having an "open issues" draft like ICCRG is doing, let's > start with a discussion here.) > > To get the ball rolling, here are some issues (mostly courtesy of > Doug Leith): > > 1. How can we model "loss synchronisation" between flows sharing a > congested link? Theoretical models typically assume either that the > per-packet loss probability is equal for all flows (no > synchronisation) or that all flows lose a packet whenever one flow > does (perfect synchronisation). The truth is somewhere in between, > but where? How does it depend on the behaviour of the transport > algorithms? (e.g., H-TCP induces more synchronisation than Reno. > CUBIC can induce either more or less, depending on how its > fast-convergence mode behaves.) > > 2. How reliable are implicit congestion indicators? The prevailing > wisdom in the IETF seems to be that "ECN=loss = congestion, delay = > noise, nothing else is useful for congestion control". What criteria > would "delay" have to satisfy in order to be a useful indicator of > congestion? Should we listen to the average delay, the frequency with > which delay exceeds a threshold, or the jitter? > > More importantly, are there other ways the network might be telling us > things? For example, does packet reordering tell us anything? (I > believe that Van Jacobson's key insight was not "loss indicates > congestion", but that we should "listen to the network calling for > help", however it does that.) > > 3. Most internet users are now home users with dedicated bottlenecks, > rather than institutional users. Should we reconsider whether > artefacts such as phase effects deserve a place in our models? > Recently some people here at Swinburne noticed a similar effect > occurring with a single CUBIC flow on a "clean" network. Are these > artefacts or important phenomena? > > 4. What role should highly-idealised models play? Are there generic > ways to include important phenomena like jitter and loss > synchronisation into mathematical models of congestion control, or is > that too naive? > > 5. What aspects of transport protocols need to be modelled other than > their congestion control mechanisms (for which we have the ICCRG...)? > For example, are there "correctness" issues (deadlock avoidance etc) > with multi-path and multi-endpoint transport protocols? Does this > list reach the right community to address those issues? > > > Cheers, > Lachlan > > -- > Lachlan Andrew Centre for Advanced Internet Architectures (CAIA) > Swinburne University of Technology, Melbourne, Australia > <http://caia.swin.edu.au/cv/landrew> <http://netlab.caltech.edu/lachlan > > > Ph +61 3 9214 4837 > _______________________________________________ > Tmrg-interest mailing list > Tmrg-interest at ICSI.Berkeley.EDU > http://mailman.ICSI.Berkeley.EDU/mailman/listinfo/tmrg-interest
- [Tmrg] Now, where were we...? Lachlan Andrew
- [Tmrg] Now, where were we...? Larry Dunn
- [Tmrg] Now, where were we...? Michael Welzl
- [Tmrg] Now, where were we...? Stefan Hirschmann
- [Tmrg] Now, where were we...? Michael Welzl
- [Tmrg] Now, where were we...? Lachlan Andrew
- [Tmrg] Now, where were we...? Damon Wischik
- [Tmrg] Now, where were we...? Lachlan Andrew
- [Tmrg] Now, where were we...? John Heffner
- [Tmrg] Now, where were we...? Lachlan Andrew
- [Tmrg] Now, where were we...? Michael Welzl
- [Tmrg] Now, where were we...? Lachlan Andrew