Re: NDProxy issue

[Pekka Savola <pekkas@netcore.fi>]

On Fri, 19 Mar 2004, Fred Templin wrote:
> Suppose A and B have performed the initial IPv6 ND exchange,
> with the ND messages proxied by P as per the specification. But,
> suppose also that A and B negotiate IPv6 header compression, i.e.,
> they establish per-hop state that allows headers to be reconstituted
> when immutable parts are omitted over-the-wire. When A sends
> a packet with a compressed IPv6 header that is no larger than the
> MTU of segment (a->p1), but larger than the MTU of segment
> (p2->b), P will be unable to return an ICMPv6 "packet too big".

[...]

> Possible resolutions appear to be: 1) Note the path MTU black
> hole issue, 2) Recommend that IPv6 header compression be
> disabled when an NDProxy may occur along the path, 3) devise
> an alternate scheme for preventing the black holes.

FWIW, it seems obvious that we should do something like 2); Header 
Compression breaks _so_ many other things in the specs that we should 
not be trying to address it here.

Whether or not this deployment scenario is obvious enough (to be a
disallowed one) is probably a matter of opinion.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings