Date: Fri, 29 Oct 1999 18:20:30 +0200 (SAT) From: Reinier Bezuidenhout <rbezuide@oskar.dev.nanoteq.co.za> To: freebsd-hackers@freebsd.org Subject: TCP delay ack question Message-ID: <199910291620.SAA14366@oskar.dev.nanoteq.co.za>
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Hi ... We have two machines that are experiencing some interesting behaviour. The one is running a 2.1.5 FreeBSD kernel (yes old) and the other a 2.2.6-STABLE kernel (also a bit old :) ) The problem is that when transfering mail to the 2.1.5 machine it happens quite quickly, but on the 2.2.6 machine it is a lot slower. When sending from another client it is fast through both machines. After examining the packets with tcpdump, I saw that when a transfer is slow ... there are no tos flags set on the packets, when the transfer is fast .. the client sets tos 0x10 (priority) on the all the packets. I then read through TCP/IP Illustrated Vol 2 .. and came accros the TF_DELACK option which delays ACKs up to 0.5 sec with a 200ms timer interval. This seems to correlate with the slow transfers as the client would send two packets (the last with the PUSH flag set) and then the FreeBSD machine would only send the ack after 0.2 seconds. Is this correct behaviour ? The question .. Should the client always set 0x10 in the tos field ... (we don't have control over the clients) or is it possible to ignore this on the FreeBSD server (we do not yet have the sysctl option to disable the delay on acks) Thanks Reinier To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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