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Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!news.mel.connect.com.au!news.syd.connect.com.au!news.bri.connect.com.au!fjholden.OntheNet.com.au!news From: Tony Griffiths <tonyg@OntheNet.com.au> Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: PPP: horrible telnet latency with ftp Date: Tue, 26 Nov 1996 12:55:08 +1000 Organization: On the Net (ISP on the Gold Coast, Australia) Lines: 44 Message-ID: <329A5C0C.68E5@OntheNet.com.au> References: <572ue9$lqv@fox.comm.net> Reply-To: tonyg@OntheNet.com.au NNTP-Posting-Host: swanee.nt.com.au Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.0 (WinNT; I) To: caj@comm.net Pisces Iscariot wrote: > > I'm running user mode PPP. Everything works just fine except that > latency over, say, a telnet connection becomes unbelievably bad when > I am also doing an ftp transfer. I've tried messing with the MRU, to > no effect. Any other ideas? > This is a function of the fact that there is no priority given to "interactive" (eg. telnet) traffic .v. "bulk data xfer" traffic (eg. ftp) so your telnet packets each containing only 1 or 2 chars queue up behind 16KB (the default TCP window size) worth of ftp data. Basically the TOS (type of service) bits are not being set or the lower layers of the protocol stack are ignoring them (or both!!!). The only way to improve the interactive response is to lower the TCP ack window to a much smaller value and also make the MTU smaller at the same time. The MTU is easy enough but I'm not sure if you can easily adjust the TCP ack window. Try playing with- # sysctl -a | grep tcp net.inet.tcp.sendspace = 16384 <-- make these only 2048 ? net.inet.tcp.recvspace = 16384 <-- values to see it that improves telnet responsiveness (at the expense of ftp throughput of course!). > Might kernel ppp handle this a bit better? I am considering switching > anyway as I move to a dedicated link with fixed IP. Good idea? > I doubt that kernel-mode PPP will provide any better performance in this situation. > thanks, > Craig > > -- > caj@comm.net --- "Ponder this on the tree of woe." > CAUTION: operator may employ sarcasm without warning. > Don't forget government's real face: the barrel of a gun. > NEW ORLEANIANS: neworleans.personals exists. Ask your newsadmin for it. Tony