> However, like you, I just sigh when I see the behemoth detnet is building. > Does it? Well, so far the circumference seems justififiable for what they want to achieve, at least according to what I can tell from these rather still abstract concepts. >> The sort of industrial control applications that detnet is targeting >> require far lower queuing delay and jitter than fq_CoDel can give. >> They have thrown around numbers like 250us jitter and 1E-9 to 1E-12 >> packet loss probability. >> > Nonetheless, it's important to have a debate about where to go to > next. Personally I don't think fq_CoDel alone has legs to get (that) > much better. > Certainly, all you said is valid - as I stated, I mostly wanted to share the digest/the existance of the inititiative without judging/reproaching/peaching ... > I prefer the direction that Mohamad Alizadeh's HULL pointed in: > Less is More: Trading a little Bandwidth for Ultra-Low Latency in the > Data Center > > In HULL you have i) a virtual queue that models what the queue would > be if the link were slightly slower, then marks with ECN based on > that. ii) a much more well-behaved TCP (HULL uses DCTCP with hardware > pacing in the NICs). > > I would love to be able to demonstrate that HULL can achieve the same > extremely low latency and loss targets as detnet, but with a fraction > of the complexity. > Well, if it's already for specific HW, then I'd prefer to see RDMA in place right away with getting rid of IRQs and other TCP/IP specific rust along the way, at least for DC realms :) Although, this HULL might has a spin for it from economics perspective. > *For public Internet, not just for DCs?* You might have seen the work > we've done (L4S ) to get queuing delay > over regular public Internet and broadband down to about mean 500us; > 90%-ile 1ms, by making DCTCP deployable alongside existing Internet > traffic (unlike HULL, pacing at the source is in Linux, not hardware). > My personal roadmap for that is to introduce virtual queues at some > future stage, to get down to the sort of delays that detnet wants, but > over the public Internet with just FIFOs. > > Thanks for sharing, that sounds thrilling - especially the achieved latencies and the non-spec. HW needs. All the best with it, again, maybe more an economical quarrel to overcome then again. -- Besten Gruß Matthias Tafelmeier