RE: New Version Notification for draft-jiang-v6ops-incremental-cgn

["Templin, Fred L" <[e-mail]>]

> > Do you think the draft needs to do any more than recommending to
follow
> > the recommendations in 4890? It seems as if that should be
sufficient.
> 
> This should be enough.

Regarding the 4890, there is advice in that document that I
would like to understand better. In Appendix A.2, it says:

   "If a network chooses to generate packets that are no larger than the
   Guaranteed Minimum MTU (1280 octets) and the site's links to the
   wider Internet have corresponding MTUs, Packet Too Big messages
   should not be expected at the firewall and could be dropped if they
   arrive."

But, that would seem to be in conflict with the text of
Section 5 of RFC2460, where the reader is informed that
the network can return PTB messages reporting MTU values
smaller than 1280 if a protocol translator is in the path.
The host should then react to these PTBs by inserting a
fragment header with (MF=0; Offset=0) in subsequent packets.
With the (RFC4890, Appendix A.2) text however, this behavior
is suppressed.

Where did the RFC4890 text come from? And, why is it there?

Thanks - Fred
[e-mail]