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Re: Adrian Farrel's No Objection on draft-ietf-6man-ext-transmit-04: (with COMMENT)

Brian E Carpenter <brian.e.carpenter@gmail.com> Tue, 08 October 2013 00:18 UTC

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Date: Tue, 08 Oct 2013 13:17:53 +1300
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Organization: University of Auckland
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To: "C. M. Heard" <heard@pobox.com>
Subject: Re: Adrian Farrel's No Objection on draft-ietf-6man-ext-transmit-04: (with COMMENT)
References: <20131007144327.16131.88173.idtracker@ietfa.amsl.com> <Pine.LNX.4.64.1310070914240.13173@shell4.bayarea.net> <52530921.3060202@gmail.com> <Pine.LNX.4.64.1310071315370.13828@shell4.bayarea.net>
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Cc: 6man-chairs@tools.ietf.org, Adrian Farrel <adrian@olddog.co.uk>, draft-ietf-6man-ext-transmit@tools.ietf.org, ipv6@ietf.org, The IESG <iesg@ietf.org>
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On 08/10/2013 10:28, C. M. Heard wrote:
...

> Maybe I'm making too much of this.  Certainly a reasonable action 
> for a middlebox that's told to pass packets with extension header 
> types 253 and 254 is to stop parsing when it encounters those next 
> header types and forward the packet in question.  Maybe that's 
> obvious to everyone -- but it seems to me that the spec, as written, 
> is actually asking for something different.

There's no header length field in an IPv6 header. That means that
since header types 253 and 254 might be used either for experimental
extension headers or for experimental payload types, there's no
generic way for a middlebox to tell the difference. I think that's
an issue that the current draft cannot resolve. I suspect we probably
need an extra sentence to state the problem, but the authors will
wait for direction on that.

    Brian

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