Subject: Is there an official Extension Headers List?

From: "Marksteiner, Stefan" <[email-masked]>
Date: Tue, 22 May 2012 17:04:04 +0200

Hello,

I just wonder if  any *official* summarization of currently existing IPv6 extension headers exists.
The only way I found to determine all headers is to step through the IANA protocol numbers list and check in the references whether the according protocol has a defined IPv6 extension header.
As far as I see it a complete current list would be:
Hop-by-Hop Option                       0
Routing Header                               43
Fragment Header                           44
AH                                                         51
ESP                                                        50
Destination Options                       60
Mobility Header                              135
Host Identity Protocol                   139
Shim6 Protocol                                140

Is there something I missed or misinterpreted? Or is there actually an official list (a citable source would fit my needs best)?
Thanks in advance.

Cheers,

Stefan

---

From: "Duncan, Jeremy" <[email-masked]>
Date: Tue, 22 May 2012 15:33:14 +0000

yes, sect 4 of RFC 2460:

   A full implementation of IPv6 includes implementation of the
   following extension headers:

           Hop-by-Hop Options
           Routing (Type 0)
           Fragment
           Destination Options
           Authentication
           Encapsulating Security Payload

   The first four are specified in this document; the last two are
   specified in [RFC-2402] and [RFC-2406], respectively.

4.1  Extension Header Order

   When more than one extension header is used in the same packet, it is
   recommended that those headers appear in the following order:

           IPv6 header
           Hop-by-Hop Options header
           Destination Options header (note 1)
           Routing header
           Fragment header

http://www.ietf.org/rfc/rfc2460.txt

010100110110010101101101011100000110010101110010001000000100011001101001

Jeremy Duncan
Senior Director, IPv6 Network Architect Salient Federal Solutions, Inc.
(Now including SGIS & Command Information Inc.)
4000 Legato Road, Suite 600 Fairfax, VA 22033
Google Voice:  540.440.1193
[email-masked]
________________________________
From: [email-masked] [[email-masked]] on behalf of Marksteiner, Stefan [[email-masked]]
Sent: Tuesday, May 22, 2012 11:04 AM
To: [email-masked]'
Subject: Is there an official Extension Headers List?

Hello,

Cheers,

Stefan

---

From: Brian E Carpenter <[email-masked]>
Date: Tue, 22 May 2012 16:46:22 +0100

However, extension headers defined since 2460 have to be added.
That's the case for MIPv6, SHIM6 and HIP.

This matters - there are known to be boxes that discard packets
with a SHIM6 header, for example.

We do maybe need a little normative RFC on this.

Regards
   Brian Carpenter

On 2012-05-22 16:33, Duncan, Jeremy wrote:
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---

From: Jeroen Massar <[email-masked]>
Date: Tue, 22 May 2012 18:00:22 +0200

> We do maybe need a little normative RFC on this.

Isn't the proper location for this:
http://www.iana.org/assignments/ipv6-parameters/ipv6-parameters.xml

Though that just points to:
http://www.iana.org/assignments/protocol-numbers/protocol-numbers.xml

as those are all the protocol numbers.

The "problem" with that list is that it is not noted explicitly as being
a Extension Header, thus IMHO it would be best if IANA could add a flag
or so to indicate that a certain protocol number is explicitly used as a
IPv6 Extension Header.

Greets,
 Jeroen

---

From: "Marksteiner, Stefan" <[email-masked]>
Date: Tue, 22 May 2012 21:40:03 +0200

That's exactly what I've meant in the first place - looking for a place for citations, the IANA protocol numbers site would have been the first place where I would look for such information.

Greetings,

Stefan
________________________________________
Von: [email-masked] [[email-masked]] im Auftrag von Jeroen Massar [[email-masked]]
Gesendet: Dienstag, 22. Mai 2012 18:00
An: Brian E Carpenter
Cc: Duncan, Jeremy; [email-masked]'
Betreff: Re: Is there an official Extension Headers List?

Greets,
 Jeroen

---

From: Brian E Carpenter <[email-masked]>
Date: Wed, 23 May 2012 07:54:35 +0100

I agree with that, but we seem to have a small problem.

RFC 2460 says that unrecognized extension headers should
lead to a discard and an ICMP Parameter Problem message,
and RFC 6434 confirms this - but without adding the extension
headers defined since RFC 2460. Thus the Internet is partially
opaque to MIPv6, SHIM6 and HIP, depending on which vendors
happen to allow for them.

Regards
   Brian

---

From: Ole Trøan <[email-masked]>
Date: Wed, 23 May 2012 09:47:28 +0200

Brian,

> happen to allow for them.

RFC2460:
   With one exception, extension headers are not examined or processed
   by any node along a packet's delivery path, until the packet reaches
   the node (or each of the set of nodes, in the case of multicast)
   identified in the Destination Address field of the IPv6 header.

cheers,
Ole

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From: Brian E Carpenter <[email-masked]>
Date: Wed, 23 May 2012 10:52:55 +0100

>    identified in the Destination Address field of the IPv6 header.

I wish it was true. There are definitely boxes that are opaque to
unrecognized headers. You are correct that the text in 2460 about
discard is not supposed to apply to forwarding nodes, which are only
supposed to examine the hop-by-hop options header, but this seems to
have been misunderstood by some implementors.

    Brian

---

From: John Leslie <[email-masked]>
Date: Wed, 23 May 2012 09:38:59 -0400

Brian E Carpenter <[email-masked]> wrote:
> On 2012-05-23 08:47, Ole Tr??an wrote:
>> Brian E Carpenter <[email-masked]> wrote:
>> 

   (This, of course, is wrong: we really-should fix it.)

   RFC 6564 "updates" RFC 2460, but this is easily missed, especially
since it has no text to contradict the "should discard" message of
RFC 2460.

   But the mere existence of possible extension headers unknown at the
time a particular IPv6 node's software was written implies that sometime
some node will encounter a newly-defined header; and an always-discard
rule is unduly limiting.

   (IMHO, of course; but anyone disagreeing is WRONG!)

>>    identified in the Destination Address field of the IPv6 header.

   That has always been clear to me: "Don't look; don't tell!"

> have been misunderstood by some implementors.

   Alas, "Don't look" is also unworkable: we should recognize the reality.

   There _will_ be middleboxes that look; many of them will discard: this
is damage to route-around if we can. Nothing we write in RFCs will stop
middleboxes from discarding stuff.

   But such behavior is not helpful; and it's very sad that RFC 2460
seems to endorse it.

   We should have a clear path for extending the list of extension
headers (and especially for finding more middle-ground between _every_
hop must process and _no_ hop should process before the destination).
Perhaps all the examples we can think of right now beg for "Experimental"
status; but the time will come when we reach consensus some such animal
should be standardized.

--
John Leslie <[email-masked]>