Date: Sun, 2 Jul 1995 09:26:13 +0300 From: Petri Helenius <pete@sms.fi> To: jleppek@suw2k.ess.harris.com (James Leppek) Cc: freebsd-questions@freefall.cdrom.com Subject: Re: tcpblast Message-ID: <199507020626.JAA19099@silver.sms.fi> In-Reply-To: <9507020111.AA00633@borg.ess.harris.com> References: <9507020111.AA00633@borg.ess.harris.com>
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James Leppek writes: > Pete, > > You may have something there. > if I leave the mtu at 16384 I get a thruput of 2.1 Mbytes/s > but it drops to .1 after a few test. If I change the mtu > to 1500 a get a thruput of 1.3Mbytes/s but no stalls. > Sounds more like it. The mecanics of tcp vary from implementation to another but take a look at ftp://ftp.scs.leeds.ac.uk/atm/doc/tcp-deadlock.ps for a review what might be happening. The document is not the whole truth, I've seen the deadlock to appear even more easily. > Would it be better to change the default mtu for lo0 to a smaller > value as a default?? If I use an mtu of 6000 the thruput is at 2Mbytes/s > with no stalls. > Safe value half of the default window. I think window is 16384 in FreeBSD so something around 8000 should work best. Some applications do lower or raise the window to get special loading/throughput requirements filled. Raising the default window is very bad idea. (not that I'm suggesting that you were doing it) > Hmmm is this thread starting to belong in hackers :-) > I that case, keep me in, unfortunately the general volume of it too much for me to just watch the networking-related issues... > Jim > Pete
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