Date: Tue, 14 Apr 1998 10:00:19 -0500 From: Dan Nelson <dnelson@emsphone.com> To: Open Systems Networking <opsys@mail.webspan.net>, freebsd-hackers@FreeBSD.ORG Subject: Re: BSDI window size sysctl wont stick Message-ID: <19980414100019.A2933@emsphone.com> In-Reply-To: <Pine.BSF.3.95.980414051535.6798E-100000@orion.webspan.net>; from "Open Systems Networking" on Tue Apr 14 05:20:28 GMT 1998 References: <Pine.BSF.3.95.980414051535.6798E-100000@orion.webspan.net>
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In the last episode (Apr 14), Open Systems Networking said: > > I recently convinced my local ISP to change the window sysctl on > their bsdi box from 8K to 16K for performance. Well it is now changed > but tcpdump still shows the BSDI box using 8K window sizes. Yow. BSD/OS defaults to 8K? > 04:17:42.626278 ip: well021.hit.net.3022 > horizon.hit.net.http: P > 4261291271:4261291596(325) ack 3944625748 win 17376 <nop,nop,timestamp > 358294 5754249> (DF) (ttl 64, id 51613) > 04:17:43.084940 ip: horizon.hit.net.http > well021.hit.net.3022: P > 3944625748:3944625921(173) ack 4261291596 win 8760 <nop,nop,timestamp > 5754250 358294> (DF) (ttl 61, id 27682) ^^^^ > > I'm overlooking something. When you change the sysctl for send > receive space on FreeBSD it takes effect immediately. On this BSDI > 3.1 server when you change the sysctl mib it seems to have no effect. I see this sometimes on FreeBSD too (I upped my windows to 32k), but what happens is the window size STARTS at 32k, but shrinks by the amount sent for each packet, until it reaches 16k. Then it stays at 16k. Try tcpdumping a session again, but look at the advertised window sizes for the first few packets. When I'm talking to other machines that I have raised the window size for, the window stays at 32k. I think it has to do with the capabilites of the other end somehow. -Dan Nelson dnelson@emsphone.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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