From owner-freebsd-net Sat Aug 10 19:55: 1 2002 Delivered-To: freebsd-net@freebsd.org Received: from mx1.FreeBSD.org (mx1.FreeBSD.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id C533837B400 for ; Sat, 10 Aug 2002 19:54:58 -0700 (PDT) Received: from patrocles.silby.com (d161.as14.nwbl0.wi.voyager.net [169.207.136.35]) by mx1.FreeBSD.org (Postfix) with ESMTP id 5939443E6A for ; Sat, 10 Aug 2002 19:54:57 -0700 (PDT) (envelope-from silby@silby.com) Received: from patrocles.silby.com (localhost [127.0.0.1]) by patrocles.silby.com (8.12.5/8.12.5) with ESMTP id g7B2wUB1062980; Sat, 10 Aug 2002 21:58:30 -0500 (CDT) (envelope-from silby@silby.com) Received: from localhost (silby@localhost) by patrocles.silby.com (8.12.5/8.12.5/Submit) with ESMTP id g7B2wROX062977; Sat, 10 Aug 2002 21:58:28 -0500 (CDT) X-Authentication-Warning: patrocles.silby.com: silby owned process doing -bs Date: Sat, 10 Aug 2002 21:58:27 -0500 (CDT) From: Mike Silbersack To: Oleg Polyakov Cc: freebsd-net@freebsd.org Subject: Re: Initial congestion window increase In-Reply-To: <20020809201429.56558.qmail@web10407.mail.yahoo.com> Message-ID: <20020810215044.O62906-100000@patrocles.silby.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org On Fri, 9 Aug 2002, Oleg Polyakov wrote: > Here is a patch allowing to increase TCP's initial congestion > window up to 4 mss but less then 4380 bytes as specified in > experimental RFC 2414 and draft-ietf-tsvwg-initwin-04.txt. > It doesn't touch idle congestion window as per draft. Despite this change being in an RFC, I'm not sure that it's really worth implementing. While increasing the slowstart flightsize might do wonders for benchmarks of short connections, the actual effect on real world tests seems much more murky. I believe that there _is_ an argument for using mss * 2 as the default flightsize, however. Supposedly, some OSes using delayed ACKs will delay the first ack, causing a 200ms delay which can really slow down the transfer of small web pages / etc. If you can find (tcpdump) evidence to back this up, I could agree with raising the value to 2 * mss. Beyond that, however, seems like a cheap way to inflate benchmarks and cause congestion. Mike "Silby" Silbersack To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message