Hi Pete,
> On Nov 28, 2023, at 13:57, Pete Heist via Ecn-sane > <[email protected]> wrote: > > Regarding the per-route ecn_low feature in BBRv3: > https://github.com/google/bbr/blob/v3/README.md#introducing-the-ecn_low-per-route-feature > > When set, any incoming CE marks from an ecn_low flagged route will be > treated as an L4S/RFC9331 CE, while CE marks from routes without that > flag will be treated as a regular RFC3168 CE. I am probably blind, but looking at https://github.com/google/bbr/blob/v3/net/ipv4/tcp_bbr.c I do not see this fall back to a rfc3168 compliant response, as far as I read this this is DCTCP or nothing... Or did you just mean that BBRv3 will treat CE just like BBRv1 and silently ignore it? > Obviously this is > problematic, as the two CE marks mean very different things, and > outside of closed environments, there's no reliable way to know which > type of CE you're receiving. The consequences of confusing them range > from massive self-induced bloat, to driving competing traffic in the > same queue down to minimum cwnd. The solution here is to just punt, so > at least tests and demos can be made to work. The per-route feature looks like a desirable safety... as does the default 5ms rtt "low-pass", where IIUC ECN will only be evaluated if the RTT is below 5ms... > This isn't a problem with BBR. The problem is, we've started an > experiment [RFC9331] that redefines the meaning of CE in a way that's > incompatible with existing RFC3168 middleboxes. This feature in BBR is > just a reflection of that. CCA developers are now tasked with somehow > deciding which type of CE they're seeing. > > Speaking of ecn "sane", does anyone else see this as not? :) and as a > problem that needs solving? Yes, however I assume this will solve it self, as is this usage of CE is over-promising and under-delivering, so I do not see this "winning the internet" in spite of the amount of thrust is put behind it... Regards Sebastian > > Pete > > _______________________________________________ > Ecn-sane mailing list > [email protected] > https://lists.bufferbloat.net/listinfo/ecn-sane _______________________________________________ Ecn-sane mailing list [email protected] https://lists.bufferbloat.net/listinfo/ecn-sane
