Re: Is there an official Extension Headers List?

[Brian E Carpenter <[e-mail]>]

On 2012-05-23 08:47, Ole Trøan wrote:
> Brian,
> 
>> 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.
> 
> 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.

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