Article: 5893 of comp.dcom.lans.ethernet Newsgroups: comp.dcom.lans.ethernet From: vjs@calcite.rhyolite.com (Vernon Schryver) Subject: Re: But errors are bad (was Re: Collisions Are Good) Message-ID:Organization: Rhyolite Software Date: Mon, 21 Feb 1994 21:16:40 GMT References: <5a.3016.308.0N1C9C42@ase.com> <2kack1$g8f@news.iastate.edu> Lines: 24 In article <2kack1$g8f@news.iastate.edu> john@iastate.edu (John Hascall) writes: >Vernon Schryver answers: > > One thing to watch (which I haven't seen mentioned this time around), > is packets lost or mangled. 1% lost or corrupt *will* definitely > degrade your performance (esp. some protocols). > > Let's take NFS with the default timeo=7 and lets assume normally > you can transmit 1MB as 1000 packets of 1KB in 1 second (1MB/s) > [round numbers for easy math :) ]. Now imagine dropping 10 > (1%) of those and waiting the retry interval of 0.7 second each. > It now takes 1 + (10 * 0.7) = 8 seconds = 0.125MB/s. > Even if you drop all the way down to timeo=2, that's 3 secs = 0.333 MB/s. That's a good point. One of the favored ways to lose 1% of your packets and so 90% of your performance is to have a "late collision" rate of 1%. Late collisions are catasrophically bad. Collisions are good. Vernon Schryver vjs@rhyolite.com
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