From owner-freebsd-net Sun Nov 28 15:41:54 1999 Delivered-To: freebsd-net@freebsd.org Received: from implode.root.com (root.com [209.102.106.178]) by hub.freebsd.org (Postfix) with ESMTP id 2360415610 for ; Sun, 28 Nov 1999 15:41:50 -0800 (PST) (envelope-from dg@implode.root.com) Received: from implode.root.com (localhost [127.0.0.1]) by implode.root.com (8.8.8/8.8.5) with ESMTP id PAA24893; Sun, 28 Nov 1999 15:41:48 -0800 (PST) Message-Id: <199911282341.PAA24893@implode.root.com> To: Mohit Aron Cc: freebsd-net@FreeBSD.ORG Subject: Re: interaction between Nagle's algorithm and TCP delayed ACKs In-reply-to: Your message of "Sun, 28 Nov 1999 14:27:08 CST." <199911282027.OAA04627@cs.rice.edu> From: David Greenman Reply-To: dg@root.com Date: Sun, 28 Nov 1999 15:41:48 -0800 Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org > FreeBSD-2.2.6 had a macro called ACK_HACK in /sys/netinet/tcp_input.c >that was effective in avoiding the undesirable interactions between the >TCP Nagle's algorithm and the delayed ACKs. Basically, if the PUSH flag I just remembered why I removed it: One of the original purposes behind delayed ACKs was to delay the ACK so that it could be combined with the character echo in the telnet/login session case. Since PUSH will usually always be set by the sender when he's typing along, the above TCP_ACK_HACK would effectively disable delayed ACKs for the case that they were created for in the first place - to aggregate the ACK with the character echo. At the time I thought that this was a bad idea. I've since changed my opinion on the usefulness of delayed ACKs, however, and now think that they cause more problems then they solve and should be shut off by default (i.e. change net.inet.tcp.delayed_ack default from 1 to 0)...which is what I do on all of the servers that I've built. -DG David Greenman Co-founder/Principal Architect, The FreeBSD Project - http://www.freebsd.org Creator of high-performance Internet servers - http://www.terasolutions.com Pave the road of life with opportunities. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message