Thanks Dave for reading this ID and providing your comments. It's really good to explore what may be missing.
> Dave Taht <dave.t...@gmail.com> wrote: >> >> section 6 addition. (could use more verbiage) >> >> 6.3 "An AQM that is ECN aware MUST have overload protection. > > I fear I cannot discern what you mean this to say. :^( > >> It is trivial for a malbehaved application/worm/bot to mark all >> its packets with ECN and thus gain priority over other traffic >> not ecn marked. > > This somewhat-paranoid claim rests on several assumptions that I > hope we will recommend against. > > - the most obvious is an assumption that a tail-drop node will mark > _instead_ of dropping ECN-capable packets. This is not actually > possible, and I hope we will strongly deprecate it. Tail-drop should > drop packets regardless of ECN bits. > > - there is also an assumption that an ECN-capable transport can mark > its packets as ECN-capable and then never reduce its sending rate. > I suppose it could; but not-ECN-capable transports can also never > reduce the sending rate. :^( And the not-ECN-capable transports > could accomplish the same reduction in "lost" packets by FEC. > > I believe we are going to "suggest" a lower marking threshhold for > ECN-capable packets than the dropping threshhold for not-ECN-capable > packets at AQM-capable nodes. This should reduce the paranoia level, > I hope, since the ECN-capable flows will get congestion signals when > not-ECN-capable packets are _not_ being dropped. > > We should concentrate our efforts on providing useful signals: > that some transports might make poor use of these signals is beyond > our scope. > I understand that router overload needs to be considered in the design of an AQM algorithm, but I inclined to think there is not much say to application designers, and that this need may have been said said in the AQM Recommendations document. Agreeing with John, I don't see this as the place to start putting detail on how routers implement AQM. >> 6.4 Enabling ECN at the application layer requires access to the IP >> header fields, which are usually abstracted out completely at the >> tcp layer, and hard to access from udp with multiple non-portable >> methods to do so. > > Yes, there are TCP stacks which are ECN-unfriendly; but there are > enough _today_ which are friendly to ECN. > I also agree with what you say - although, again I'm not sure we need to add this here, I think the design of transports is really the topic of RFC5405.bis, >> ECN over UDP in new applications such as webrtc and Quic has >> great potential for many other applications, however the same >> care of design that went into ECN on TCP needs to go into >> future UDP based protocols. > > I wouldn't disagree; but those issues are essentially-solved > problems today. > >> Some other section that may end up here? >> >> ECN marking other sorts of flows (example routing packets) that have a >> higher priority than other flows on link-local packets may be of benefit >> with wider availability of aqm technologies that are ecn aware... > I'm not sure I understand what you are suggesting with respect to ECN. > I suppose there might be _some_ use for ECN on routing packets; but > I doubt this is desirable today. ECN is not-at-all about getting a > higher priority -- it's about getting congestion signals without > packet loss. > I think the IETF would normally recommend diffserv priority marking for network control traffic. > -- > John Leslie <j...@jlc.net> > Gorry _______________________________________________ aqm mailing list aqm@ietf.org https://www.ietf.org/mailman/listinfo/aqm
