From owner-freebsd-current@FreeBSD.ORG Fri Jul 27 18:10:26 2007 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 2281B16A41F for ; Fri, 27 Jul 2007 18:10:26 +0000 (UTC) (envelope-from iaccounts@ibctech.ca) Received: from pearl.ibctech.ca (pearl.ibctech.ca [208.70.104.210]) by mx1.freebsd.org (Postfix) with ESMTP id B0AD813C45A for ; Fri, 27 Jul 2007 18:10:25 +0000 (UTC) (envelope-from iaccounts@ibctech.ca) Received: (qmail 61884 invoked by uid 1002); 27 Jul 2007 17:43:45 -0000 Received: from iaccounts@ibctech.ca by pearl.ibctech.ca by uid 89 with qmail-scanner-1.22 (spamassassin: 2.64. Clear:RC:1(208.70.104.100):. Processed in 6.28211 secs); 27 Jul 2007 17:43:45 -0000 Received: from unknown (HELO ?192.168.30.110?) (steve@ibctech.ca@208.70.104.100) by pearl.ibctech.ca with (DHE-RSA-AES256-SHA encrypted) SMTP; 27 Jul 2007 17:43:38 -0000 Message-ID: <46AA2ED3.6050702@ibctech.ca> Date: Fri, 27 Jul 2007 13:43:47 -0400 From: Steve Bertrand User-Agent: Thunderbird 2.0.0.5 (Windows/20070716) MIME-Version: 1.0 To: freebsd-current@freebsd.org X-Enigmail-Version: 0.95.1 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: IP header question X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 27 Jul 2007 18:10:26 -0000 First of all, sorry for being off topic here, but I know there are many people in this list that know the network stack inside and out. I have (hopefully) a couple very easy questions: When the term 'header stripping' is used as a packet is passed up the stack, what really happens? I don't understand how if a layers header is 'stripped off' as it goes up, it will know where to be sent to as it goes back down. Does 'stripping' mean simply reading it on the way up (but not discarding)? If so, when does the src/dst info for layer-3 and layer-2 get reversed, on the way up, or the way back down? If not, how does each layer know what destination information to insert into the headers for the trip back to the source? Thanks very much for any insight. Steve