[41379] in North American Network Operators' Group
Re: end2end? (was: RE: Where NAT disenfranchises the end-user ...)
daemon@ATHENA.MIT.EDU (Leo Bicknell)
Fri Sep 7 14:50:23 2001
Date: Fri, 7 Sep 2001 14:49:46 -0400
From: Leo Bicknell <bicknell@ufp.org>
To: Mike Batchelor <mikebat@tmcs.net>
Cc: bmanning@vacation.karoshi.com, "NANOG (E-mail)" <nanog@merit.edu>
Message-ID: <20010907144946.A57845@ussenterprise.ufp.org>
Mail-Followup-To: Leo Bicknell <bicknell@ussenterprise.ufp.org>,
Mike Batchelor <mikebat@tmcs.net>, bmanning@vacation.karoshi.com,
"NANOG (E-mail)" <nanog@merit.edu>
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In-Reply-To: <LLEOLJEDPHOFANPCPKOMOEHECEAA.mikebat@tmcs.net>; from mikebat@tmcs.net on Fri, Sep 07, 2001 at 10:55:49AM -0700
Errors-To: owner-nanog-outgoing@merit.edu
On Fri, Sep 07, 2001 at 10:55:49AM -0700, Mike Batchelor wrote:
> NAT rewrites certain packet data fields (src addr, src port, sometimes mac
> addr). So does a ordinary router (ttl decrement). One breaks end2end, the
> other does not. What is the difference?
NAT rewrite more than that, try reading
http://www.cisco.com/warp/public/cc/pd/iosw/ioft/ionetn/prodlit/1195_pp.htm
In particular, it rewrites addresses _in the data portion of the packet)
for the following protocols:
ICMP, FTP, NetBIOS, RealAudio, CuSeeMe, DNS, Netmeeting, H.323, PPTP and
several others.
That's what makes it violate the end2end principal, your _data_ is changed
by NAT.
--
Leo Bicknell - bicknell@ufp.org
Systems Engineer - Internetworking Engineer - CCIE 3440
Read TMBG List - tmbg-list-request@tmbg.org, www.tmbg.org
