> -----Original Message----- > From: Mike Silbersack [mailto:[EMAIL PROTECTED] > Sent: Tuesday, March 09, 2004 2:12 PM > To: Kevin Oberman > Cc: Brad Knowles; [EMAIL PROTECTED]; [EMAIL PROTECTED] > Subject: Re: Who wants SACK? (Re: was My planned work on networking > stack) > > > SACK itself really doesn't do much, it's all the new > congestion control > schemes (FACK, Rate Halving, etc) that come shipped with most SACK > implementations that do the work and contain most of the complexity. >
That's not quite true. Basic SACK by itself can be very helpful, especially if NewReno is the non-SACK fallback, in long delay environments characterized by bursty losses (multiple packets in one window). With NewReno, you end up only recovering one packet per RTT, which can in some cases be much worse than just taking a timeout and starting over. See below paper for some experimental traces of this: http://citeseer.ist.psu.edu/henderson99transport.html (not that I don't think that the more recent RFCs are an improvement on basic SACK) As for who/when to do this, I and perhaps others have been discouraged from taking a stab at a SACK patch in the past, because of a sentiment that it should be undertaken as part of a bigger rewrite of TCP. Tom p.s. Niels Provos ported our Berkeley BSDi-based SACK extension to OpenBSD several years ago-- that might be something to look at as a starting point. _______________________________________________ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "[EMAIL PROTECTED]"
