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 <net@freebsd.org>; 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" <ipver4@hotmail.com>
To: <paul+usenet@w6yx.stanford.edu>
Cc: <net@freebsd.org>
References: <a91v6e$1f3v$1@hairball.treehouse.napa.ca.us>
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: <OE29hkKoCoj6ULO51Sh0000d849@hotmail.com>
X-OriginalArrivalTime: 11 Apr 2002 00:13:47.0313 (UTC) FILETIME=[BFD17210:01C1E0ED]
Sender: owner-freebsd-net@FreeBSD.ORG
Precedence: bulk
List-ID: <freebsd-net.FreeBSD.ORG>
List-Archive: <http://docs.freebsd.org/mail/> (Web Archive)
List-Help: <mailto:majordomo@FreeBSD.ORG?subject=help> (List Instructions)
List-Subscribe: <mailto:majordomo@FreeBSD.ORG?subject=subscribe%20freebsd-net>
List-Unsubscribe: <mailto:majordomo@FreeBSD.ORG?subject=unsubscribe%20freebsd-net>
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