On Wednesday, February 06, 2013 6:27:04 am Randall Stewart wrote: > John: > > A burst at line rate will *often* cause drops. This is because > router queues are at a finite size. Also such a burst (especially > on a long delay bandwidth network) cause your RTT to increase even > if there is no drop which is going to hurt you as well. > > A SHOULD in an RFC says you really really really really need to do it > unless there is some thing that makes you willing to override it. It is > slight wiggle room. > > In this I agree with Andre, we should not be *not* doing it. Otherwise > folks will be turning this on and it is plain wrong. It may be fine > for your network but I would not want to see it in FreeBSD. > > In my testing here at home I have put back into our stack max-burst. This > uses Mark Allman's version (not Kacheong Poon's) where you clamp the cwnd at > no more than 4 packets larger than your flight. All of my testing > high-bw-delay or lan has shown this to improve TCP performance. This > is because it helps you avoid bursting out so many packets that you overflow > a queue. > > In your long-delay bw link if you do burst out too many (and you never > know how many that is since you can not predict how full all those > MPLS queues are or how big they are) you will really hurt yourself even worse. > Note that generally in Cisco routers the default queue size is somewhere > between > 100-300 packets depending on the router.
Due to the way our application works this never happens, but I am fine with just keeping this patch private. If there are other shops that need this they can always dig the patch up from the archives. -- John Baldwin _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
