Re: Updating to RFC6434 to deal with 8200-style header insertion by IPIP

Brian E Carpenter <brian.e.carpenter@gmail.com> Mon, 06 November 2017 19:35 UTC

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Subject: Re: Updating to RFC6434 to deal with 8200-style header insertion by IPIP
To: Fernando Gont <fernando@gont.com.ar>, "C. M. Heard" <heard@pobox.com>, 6man WG <ipv6@ietf.org>
Cc: Michael Richardson <mcr+ietf@sandelman.ca>
References: <CACL_3VETxNVQ+YD5j6ZiWjycQ=ojAuWwB23offNdVKm+S9c_7A@mail.gmail.com> <23308.1509623865@obiwan.sandelman.ca> <CACL_3VFrcombGczXU6Zz=Pk1u2GE=wGG-r+yEefdHai1REqXmQ@mail.gmail.com> <c8911f45-2afc-9d26-c0a8-1017d034a251@gmail.com> <1e62fab6-c434-a474-e53b-e4c7f2d83de0@gont.com.ar>
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Organization: University of Auckland
Message-ID: <5cb2b9fd-8546-31fd-d984-d161aef16349@gmail.com>
Date: Tue, 7 Nov 2017 08:35:03 +1300
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Hi Fernando,

On 07/11/2017 07:02, Fernando Gont wrote:
> On 11/02/2017 04:33 PM, Brian E Carpenter wrote:
>> On 03/11/2017 04:26, C. M. Heard wrote:
>>> On Thu, Nov 2, 2017, Michael Richardson <mcr+ietf@sandelman.ca>; wrote:
>>>
>>>>
>>>> C. M. Heard <heard@pobox.com>; wrote:
>>>>     > On Wed, 01 Nov 2017, Michael Richardson wrote:
>>>>     >> Yet we skip other extension headers in order to find the ULP.
>>>>
>>>>     > Not so. An end node that encounters an unrecognized extension header
>>>> is
>>>>
>>>> Both AH and IPIP are well known and recognized extension headers.
>>
>> AH is an extension header. "IPIP" isn't. It's Protocol 41, and Protocol 41
>> is otherwise known as IPv6. (That's why it's also called IPPROTO_IPV6).
>> In RFC8200 terms that makes it an "upper-layer header". Strictly speaking,
>> RFC8200 doesn't specify what to do with an unrecognized upper-layer header.
> 
> Based on the std, anything that is unknown is an EH. In the context of
> RFC8200/FC2460, there's only:
> 
> * Known EHs
> * Known ULP
> * Unknown EHs

Yes, that's what the text says but I wish we'd fixed it in 8200 to
acknowledge that there is a 4th case (Unknown ULP) and that it
cannot be distinguished from the 3rd case. Acknowledging that is
much better than ignoring it. I'm happy with Ole's suggestion that
this (and the resulting ICMP 1 behaviour) should be mentioned in
6434bis - as a clarification, not a new invention.

I also agree that there are enough potential issues in unexpected
IPv6-in-IPv6 that is deserves its own draft.

Regards
   Brian
 
> with the last one being the default branch :-)
> 
>