> "TCP Implementation Enhancements for Improving Webserver
> Performance"

I took a quick read of this paper while injesting my morning
caffeine a few moments ago.  There are some very interesting ideas
in here, but I wanted to note one thing about the RTO timers.  Vern
Paxson and I have plumbed some of these waters and found that the
single biggest property a good estimator should have is a fairly
large minimum RTO, which the proposal in the above paper does not
provide.  In our analysis of a large number of TCP connections over
~1000 Internet network paths we found that by making the RTO more
aggressive you increased the number of spurious retransmissions by a
fairly hefty amount (which also hurts performance).  The following
paper details our findings:

    Mark Allman, Vern Paxson. On Estimating End-to-End Network Path
    Properties. ACM SIGCOMM, September 1999.  To appear. 
    http://roland.grc.nasa.gov/~mallman/papers/estimation.ps

So, the point that I am attempting to convey to the NetBSD TCP folks
is that it seems as if the jury is still out on how to do RTO timers
right.  My opinion is that further Internet testing is required
before we have an extremely good understanding of RTO estimators and
therefore it may not be a good time to go messing with the
production netbsd code.  

Just my $0.02!

allman


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http://roland.grc.nasa.gov/~mallman/