From owner-freebsd-net Wed Apr 10 17:13:51 2002 Delivered-To: freebsd-net@freebsd.org Received: from hotmail.com (oe29.law14.hotmail.com [64.4.20.86]) by hub.freebsd.org (Postfix) with ESMTP id 789F337B405 for ; Wed, 10 Apr 2002 17:13:47 -0700 (PDT) Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Wed, 10 Apr 2002 17:13:47 -0700 X-Originating-IP: [138.89.21.26] From: "ipver4" To: Cc: References: Subject: Re: TCP Timestamp option? Date: Wed, 10 Apr 2002 20:13:38 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 Message-ID: X-OriginalArrivalTime: 11 Apr 2002 00:13:47.0313 (UTC) FILETIME=[BFD17210:01C1E0ED] 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 Thanks for the explanation. It seems since version 4.4 that kernel net.inet.tcp.rfc1323 is set to 1 by default, thus causing all the TCP connections to use the RFC1323 extension. The effects are: 1. bigger TCP header. 2. more processing time at sending and receiving hosts. 3. VJ TCP/IP header compression algorithm does not compress most of the time. I am not sure turning on the RFC1323 support on by default is such a good idea. > The TCP timestamp option is used to obtain better round-trip time > estimates than can be obtained without, and these estimates turn out > to be important in networks with large bandwidth*delay products. > > Timestamps in the timestamp option also cycle much more slowly than > sequence numbers on an active high-speed connection and can thus be used > to detect and discard old duplicate packets with apparently valid sequence > numbers. > > RFC 1323 explains the details. > -- > G. Paul Ziemba paul@w6yx.stanford.edu > FreeBSD unix: > 11:06AM up 16 days, 14 mins, 7 users, load averages: 0.03, 0.03, 0.00 > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-net" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message