[Bloat] Comcast & L4S

[Sebastian Moeller]

Hi Jonathan,


> On 1. Feb 2025, at 15:51, Jonathan Morton <chromatix99 at gmail.com> wrote:
> 
>> On 1 Feb, 2025, at 4:33 pm, Sebastian Moeller via Bloat <bloat at lists.bufferbloat.net> wrote:
>> 
>> …Comcast's use of the Internet Engineering Task Force's Low Latency Low Loss Scalable Throughput (L4S) standards…
> 
> That's the tail wagging the dog - but precisely the kind of non-specialist misunderstanding that L4S' hijacking of the IETF process was designed to foster.

To me it made fully clear that the IETF process is really a mess, I witnessed it going splendidly in other WGs, but that required good-faith and gentlemanly sportsmanship from all sides. L4S/NQB showed how easily this process can be derailed... 


> It's an EXPERIMENT that the IETF has been BROWBEATEN by Comcast into PERMITTING to occur.  It is NOT a STANDARD, and it was NOT IETF-led.  Every single design suggestion that IETF proposed, to improve coexistence with other schemes that ARE IETF standards, was resisted or outright ignored.

Well, my take is, low latency docsis had already been mostly or even fully specified by that time, and so the only changes accepted were those that had zero implications for LLD... so mostly shuffling verbiage around. But yeah the whole ram this though the IETF smells party as a method to create plausible deniability once things turn out not to be working all that well (and pessimistically assuming there is no real fix for the failure modes).


> As with NQB, Cake already does essentially what L4S requires, except for default-configured Codel being less than ideal as an AQM for producing congestion signals for a DCTCP-type response.  I have no intention of modifying Cake to *specifically* accommodate L4S in any way.  If their crap doesn't work properly in a standards-compliant environment, that's THEIR problem.

Now, as advocatus diabolical, the way CoDel works we have interval and/or target as configurable parameters and a trade-off between maintaining utilisation over the wider internet and keeping the signalling reactive for closer by flows, maybe we could teach cake to allow a second set of interval/(automatically calculated) target to optimise for local and non local traffic, and use a proper (configurable and maskable) DSCP/TOS to steer packets into this? Maybe CS7 would do to signal its intent for local delivery?


> - Jonathan Morton