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Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!nntp.coast.net!news.kei.com!news.mathworks.com!EU.net!Norway.EU.net!online.no!sn.no!hermod.uio.no!nntp.uio.no!nntp.uib.no!nntp-bergen.UNINETT.no!nntp-trd.UNINETT.no!not-for-mail From: sthaug@nethelp.no (Steinar Haug) Newsgroups: comp.os.linux.networking,comp.unix.bsd.bsdi.misc,comp.unix.bsd.misc Subject: Re: Linux vs BSD Date: 28 Jan 1997 21:07:30 GMT Organization: Nethelp Consulting, Trondheim, Norway Lines: 23 Message-ID: <5clpqi$pj7@verdi.nethelp.no> References: <32DFFEAB.7704@usa.net> <5c8ifp$445@cynic.portal.ca> <5c8vvb$5uh@lynx.dac.neu.edu> <32E89205.41C67EA6@FreeBSD.org> <5cabgm$hp0@fg70.rz.uni-karlsruhe.de> <5chl91$bsi@usenet.srv.cis.pitt.edu> <87d8uqu5vt.fsf@localhost.xs4all.nl> NNTP-Posting-Host: aun.uninett.no In-reply-to: Peter Mutsaers's message of Mon, 27 Jan 1997 22:09:58 GMT Xref: euryale.cc.adfa.oz.au comp.os.linux.networking:66476 comp.unix.bsd.bsdi.misc:5775 comp.unix.bsd.misc:2089 [Peter Mutsaers] | On a very clean ethernet the maximum you can get is 10mbit/s /8 is | 1.25mbyte/s. The maximum packet size is 1500 bytes, in this you have | overhead of at least 5 percent because of layer 2,3 and 4 headers (up | to TCP). So not counting the (quite large) overhead of fragmentation | (8k NFS packets get fragmented on ethernet) and NFS headers, e.g. a | plain FTP transfer, 1000kb/s is the absolute maximum. Your figure of 5% overhead is about right (1538/1460=1.0534), but your conclusion is wrong. That overhead means you still have a theoretical bandwidth (not counting acks) of around 1159 kByte/s. According to Vernon Schryver, the "speed of light" for TCP on Ethernet, if you can avoid the capture effect, is around 1150 kByte/s. I have measured 1100 kByte/s myself on an otherwise quiet Ethernet using ttcp. I tend to believe my measurements - I've looked at the ttcp code, and the measurement was easily reproducible. Mind you, I haven't said *anything* here about NFS - this is all about raw TCP bandwidth. Steinar Haug, Nethelp consulting, sthaug@nethelp.no