Re: [tsvwg] path forward on L4S issue #16
Sebastian Moeller <moeller0@gmx.de> Wed, 17 June 2020 17:11 UTC
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From: Sebastian Moeller <moeller0@gmx.de>
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Date: Wed, 17 Jun 2020 19:10:38 +0200
Cc: "Rodney W. Grimes" <ietf@gndrsh.dnsmgr.net>, Jonathan Morton <chromatix99@gmail.com>, "tsvwg@ietf.org" <tsvwg@ietf.org>
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References: <2DC5C89B-C979-4354-98D7-BBDBC78A42B1@gmail.com> <202006171419.05HEJClG085550@gndrsh.dnsmgr.net> <HE1PR0701MB287641121218FC0AA72F56B0C29A0@HE1PR0701MB2876.eurprd07.prod.outlook.com>
To: Ingemar Johansson S <ingemar.s.johansson@ericsson.com>
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Subject: Re: [tsvwg] path forward on L4S issue #16
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Hi Ingemar, more below in-line... > On Jun 17, 2020, at 18:27, Ingemar Johansson S <ingemar.s.johansson@ericsson.com> wrote: > > Hi > > OK, I see that this discussion is only going in circles, nearly giving up on > this. > So far I see only one firm evidence that RFC3168 AQMs are deployed and > enabled and these are related to the OpenWrt project, manifested in a few > upgradeable devices (and some not upgradeable) that can be bought in retail > stores. The rest is unconfirmed. > > This leads me to a look at the time line for L4S and how it correlates with > the fq-codel work and as a consequence the OpenWrt project. > > 1) L4S was first brought up late 2013-early 2014 in TSVWG. The ECN > experimentation draft (now RFC8311) was a draft -00 in sept 2016 and I know > that this draft was preceeded by a discussion in TSVWG before that > > 2) The FQ-codel work was finalized early 2016, not quite a perfect overlap > with the 00 version of the ECN experimentation work but definitely an > overlap with the preceeding L4S and dualQ discussions and references to the > RITE project which happened around 2014-2015. The ACM codel paper is from 2012... And fq_codel was deployed well before the matching RFC was published by the IETF. By virtue of being rdf3168 compliant deploy first standardize later was a viable way forward for codel/fq_codel. If only L4S would have selected an incrementally roll-out-able path, we would not be here right now. > > With that in mind, shouldn't it have been on the table to consider the > possible future existence of L4S in the different realizations of fq-codel > (and OpenWrt) development? [SM] -ENOTIMEMACHINE, at the current time, L4S is not standardized and hence there is neither a known working implementation (tested internet wide) nor an accepted standard to work against. > > Issue #16 is pretty much a consequence of the above timeline, [SM] That seems wishful thinking to me. #16 is a direct consequence of L4S decision to violate precedence and redefine the meaning of CE, plain and simple. The only thing where fq_codel got involved is in being a pretty good all around qdisc for tcp-friendly traffic and hence seeing decent deployment in Linux (and as I might add in Macs as it seems). Yes, that attractiveness has increased L4S' predicament, but it is NOT the root cause, let us please not confuse this here. > I see that > there was ample time to react but that reaction did not come until 2019 (or > late 2018?), was any assessment done as regards to how L4S could coexist > with fq-codel before the debate started in TSVWG?. I note that for the longest time rfc3168 compatibility was on the todo list of L4S. Only when team L4S was trying to get that requirement dropped* instead of actually tackling the issue the topic came to the fore on the tsvwg mailing list and meetings. Best Regards Sebastian > > /Ingemar > > > > >> -----Original Message----- >> From: Rodney W. Grimes <ietf@gndrsh.dnsmgr.net> >> Sent: den 17 juni 2020 16:19 >> To: Jonathan Morton <chromatix99@gmail.com> >> Cc: Ingemar Johansson S <ingemar.s.johansson@ericsson.com>; Ingemar >> Johansson S <ingemar.s.johansson=40ericsson.com@dmarc.ietf.org>; >> tsvwg@ietf.org >> Subject: Re: [tsvwg] path forward on L4S issue #16 >> >>>> On 17 Jun, 2020, at 4:20 pm, Ingemar Johansson S >> <ingemar.s.johansson@ericsson.com> wrote: >>>> >>>> Given all the input sofar my impression is that It is difficult to say > how >> serious issue 16 really is. >>>> Surely there is a possibility that L4S flows can get an potentially > unfair >> advantage over a congested node that is RFC3168 capable (and ECN >> enabled). The question is here when things are deemed as unfair and when >> starvation is a fact, opinions differ. >>>> Another question is to how large extent there will be legacy RFC3168 > ECN >> capable (and ECN enabled ) bottlenecks that will "never" be updated or >> replaced. This question is currently difficult to answer. >>> >>> When questions such as these are "difficult to answer", the correct > design >> choice is to assume pessimistically, unless and until the question can be >> answered more definitively. Therefore, the L4S design must account for > the >> possibility of RFC-3168 AQMs in the network, and actively avoid unfairness > in >> that case. >>> >>>> Yet another aspect is how successful it will be to implement RFC3168 >> bottleneck detection e.g. in TCP Prague, I am quite confident that these > will >> not always be successful. >>> >>> I think we can safely say that the detection mechanism currently in TCP >> Prague is not successful. David Black also pointed out that this would > always >> be a fragile mechanism, difficult to implement correctly, and thus likely > to be >> implemented wrongly by other transports even if a workable version was >> somehow developed. >>> >>> With these facts established, I do not see how L4S can proceed without >> changing the signalling mechanism it uses. This is something we > intuitively >> realised more than a year ago, when the SCE project was started, but now >> we have actual evidence to back up that intuition. >> >> And I would like to add to that, this is evidence the L4S team itself > should of >> identified, characterized and docuemented years ago. I see no reason that > it >> took team SCE to disect the failure modes of L4S so that they could be >> addressed. >> >> IMHO the fact that L4S is years into the process and only done positive > test >> results presentations leads one to believe it is simply being pushed > through >> the process with little to no care about the actual internet community. >> >> The proponents seem to genuily be a) unwilling to acknowledge that there a >> problems they should be working on, and b) presenting that L4S is ready > for >> internet deployment inlight of the fact that data showing clear and > present >> problems exist. >> >>> - Jonathan Morton >> -- >> Rod Grimes > rgrimes@freebsd.org
- [tsvwg] path forward on L4S issue #16 Wesley Eddy
- Re: [tsvwg] path forward on L4S issue #16 Black, David
- [tsvwg] FW: path forward on L4S issue #16 Black, David
- Re: [tsvwg] FW: path forward on L4S issue #16 Jonathan Morton
- Re: [tsvwg] path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] FW: path forward on L4S issue #16 Steven Blake
- [tsvwg] Options for improving L4S safety alex.burr@ealdwulf.org.uk
- Re: [tsvwg] Options for improving L4S safety Jonathan Morton
- Re: [tsvwg] FW: path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] path forward on L4S issue #16 Jonathan Morton
- Re: [tsvwg] path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] path forward on L4S issue #16 Sebastian Moeller
- Re: [tsvwg] path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] path forward on L4S issue #16 Sebastian Moeller
- Re: [tsvwg] path forward on L4S issue #16 Jonathan Morton
- Re: [tsvwg] path forward on L4S issue #16 Rodney W. Grimes
- Re: [tsvwg] path forward on L4S issue #16 Sebastian Moeller
- Re: [tsvwg] path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] path forward on L4S issue #16 Sebastian Moeller
- Re: [tsvwg] path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] path forward on L4S issue #16 Sebastian Moeller
- Re: [tsvwg] path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] path forward on L4S issue #16 Jonathan Morton
- Re: [tsvwg] path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] path forward on L4S issue #16 Sebastian Moeller
- Re: [tsvwg] path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] path forward on L4S issue #16 Rodney W. Grimes
- Re: [tsvwg] path forward on L4S issue #16 Sebastian Moeller
- Re: [tsvwg] path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] path forward on L4S issue #16 Sebastian Moeller
- Re: [tsvwg] path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] path forward on L4S issue #16 Sebastian Moeller
- Re: [tsvwg] path forward on L4S issue #16 Jonathan Morton
- Re: [tsvwg] path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] path forward on L4S issue #16 Spencer Dawkins at IETF
- Re: [tsvwg] path forward on L4S issue #16 Holland, Jake
- Re: [tsvwg] path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] path forward on L4S issue #16 Sebastian Moeller
- Re: [tsvwg] path forward on L4S issue #16 Jonathan Morton
- Re: [tsvwg] path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] path forward on L4S issue #16 Sebastian Moeller
- Re: [tsvwg] path forward on L4S issue #16 Rodney W. Grimes
- Re: [tsvwg] path forward on L4S issue #16 Wesley Eddy
- Re: [tsvwg] path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] path forward on L4S issue #16 Jonathan Morton
- Re: [tsvwg] path forward on L4S issue #16 Sebastian Moeller
- Re: [tsvwg] path forward on L4S issue #16 Black, David
- Re: [tsvwg] path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] path forward on L4S issue #16 Sebastian Moeller
- Re: [tsvwg] path forward on L4S issue #16 Sebastian Moeller
- Re: [tsvwg] path forward on L4S issue #16 Wesley Eddy
- Re: [tsvwg] path forward on L4S issue #16 Paul Vixie
- Re: [tsvwg] path forward on L4S issue #16 Wesley Eddy
- Re: [tsvwg] path forward on L4S issue #16 Holland, Jake
- Re: [tsvwg] path forward on L4S issue #16 Ingemar Johansson S
- Re: [tsvwg] path forward on L4S issue #16 Sebastian Moeller
- Re: [tsvwg] path forward on L4S issue #16 Sebastian Moeller
- Re: [tsvwg] path forward on L4S issue #16 Jonathan Morton
- Re: [tsvwg] path forward on L4S issue #16 Sebastian Moeller
- Re: [tsvwg] path forward on L4S issue #16 Holland, Jake
- Re: [tsvwg] path forward on L4S issue #16 Rodney W. Grimes
- Re: [tsvwg] path forward on L4S issue #16 Ruediger.Geib
- Re: [tsvwg] path forward on L4S issue #16 Scharf, Michael
- Re: [tsvwg] path forward on L4S issue #16 Wesley Eddy
- Re: [tsvwg] path forward on L4S issue #16 Wesley Eddy
- Re: [tsvwg] path forward on L4S issue #16 Martin Duke
- Re: [tsvwg] path forward on L4S issue #16 Holland, Jake
- Re: [tsvwg] path forward on L4S issue #16 Rodney W. Grimes
- Re: [tsvwg] path forward on L4S issue #16 Wesley Eddy
- Re: [tsvwg] path forward on L4S issue #16 Sebastian Moeller