From owner-freebsd-net@FreeBSD.ORG Fri Aug 12 20:57:37 2005 Return-Path: X-Original-To: freebsd-net@freebsd.org 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 F106A16A41F for ; Fri, 12 Aug 2005 20:57:37 +0000 (GMT) (envelope-from jha_miku@yahoo.com) Received: from web50201.mail.yahoo.com (web50201.mail.yahoo.com [206.190.38.42]) by mx1.FreeBSD.org (Postfix) with SMTP id 774D643D49 for ; Fri, 12 Aug 2005 20:57:37 +0000 (GMT) (envelope-from jha_miku@yahoo.com) Received: (qmail 26237 invoked by uid 60001); 12 Aug 2005 20:57:36 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:Received:Date:From:Subject:To:Cc:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding; b=lfxbFlvEz2NjegaZ0LLqnBuRhxWdcg6E4qqE91emEXt2dejd2Hp8NXTtQ6N5zF+xDKBvbknOZbKS6Z6Oj9Ha8I6zF9hvoNxfgHK7TZ6fN0Pqv6AFl86BMu6PTKhGx9/2Oo/X7nE9BdJBhkMCg5CWaQOxHrr5hMDHwqhYv2x8aWM= ; Message-ID: <20050812205736.26235.qmail@web50201.mail.yahoo.com> Received: from [65.113.40.130] by web50201.mail.yahoo.com via HTTP; Fri, 12 Aug 2005 13:57:36 PDT Date: Fri, 12 Aug 2005 13:57:36 -0700 (PDT) From: Miku Jha To: Chuck Swiger , jha miku In-Reply-To: <42FCFDFC.2020903@mac.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Cc: freebsd-net@freebsd.org Subject: Re: Question regd timestamp option X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 12 Aug 2005 20:57:38 -0000 --- Chuck Swiger wrote: > jha miku wrote: > > In case of active open, the SYN segments always > have > > timestamp enabled, since the RFC flg is set. But, > > Currently, I am seeing some SYN segments without > > timestamp option. > > FreeBSD (and OS X, and other things using a BSD > network stack) will generate > initial TCP SYN packets containing the "MNWNNT" TCP > options, at least by > default in the absense of other information or > settings. > > > The only condition that I am aware of when > timestamp > > is disabled, is on sending the 3rd SYN in > retransmit code > > when the timestamp gets disabled. > > looking at the tcpdump, it is unclear why the SYNs > are > > sent during active open without timestamp option. > > The TCP stack seems to remember some information > about which TCP options a > remote host is willing to accept. If the remote > system didn't accept a > timestamp the first time (perhaps it's talking to an > old windows box which does > "MNNS"), there is no point in sending that option > out the next time you open a > new connection to the same system. > The first time both ends negotiate and accept timestamp option. The situation is that if the client crashes , the server eventually sends a RST (10.39.53) Following this RST, the client comes back in lets say around 2-3 minutes. Now when the client sends a SYN(10.42.23), there is no timestamp option. Is there some requirement that RST needs to be ACKED or RST flag will remain set for some time window within which if SYN is send, timestamp option will not be set. Thanks in advance for your help. > -Chuck > > _______________________________________________ > freebsd-net@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to > "freebsd-net-unsubscribe@freebsd.org" > mailto:jha_miku@yahoo.com contact : 408 9211697. __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com