On Thu, Oct 27, 2016 at 10:52 AM, Eric Dumazet <[email protected]> wrote: > On Thu, 2016-10-27 at 10:33 -0700, Dave Taht wrote: > >> At the moment my biggest beef with BBR is that it ignores ECN entirely >> (and yet negotiates it). > > Note that switching cubic to any other CC like BBR is allowed at any > time, way after ECN was negotiated. > > So BBR can not solve the issue you mention in a reliable way. > > There must be a reason sysctl_tcp_ecn default value is 2 on linux [1], > don't you think ??? > > _You_ chose to change this sysctl, do not blame BBR for being silly !
While I chose to do so on portions of my deployment, there is the larger problem that Apple has enabled it nearly universally on iOS and OSX over the past year. > ECN was a nice attempt, but suffers from implementation bugs. Believe me, I'm not huge on it either! > > For a start, linux does not implement RFC 3540. > > If someone cares enough of ECN, then it should cook linux patches to > implement RFC 3540. Hint hint hint. > > Then you need to make sure all the nodes between your peers are not > messing with ECN. > > BBR simply works, because it is a sender side thing. > You do not have to fix everything in the Internet. > > [1] > Documentation/networking/ip-sysctl.txt > tcp_ecn - INTEGER > Control use of Explicit Congestion Notification (ECN) by TCP. > ECN is used only when both ends of the TCP connection indicate > support for it. This feature is useful in avoiding losses due > to congestion by allowing supporting routers to signal > congestion before having to drop packets. > Possible values are: > 0 Disable ECN. Neither initiate nor accept ECN. > 1 Enable ECN when requested by incoming connections and > also request ECN on outgoing connection attempts. > 2 Enable ECN when requested by incoming connections > but do not request ECN on outgoing connections. > Default: 2 > > -- Dave Täht Let's go make home routers and wifi faster! With better software! http://blog.cerowrt.org _______________________________________________ Bloat mailing list [email protected] https://lists.bufferbloat.net/listinfo/bloat
