Subject: Re: (IPng 7503) Re: Last Call: IPv6 Jumbograms to Proposed Standard

From: Steve Deering <[email-masked]>
Date: Fri, 4 Jun 1999 17:12:38 -0700

Very belated comment:

At 9:30 PM -0400 5/10/99, Steven M. Bellovin wrote:
>Bump in the wire is fine -- it's AH that's the problem.

No.  Bump-in-the-wire (or anything else that inserts extension headers
into IPv6 packets, unknown to the originating upper-layer protocol)
breaks other things as well as AH, for example fragmentation-avoidance
through MTU discovery, and the TCP MSS mechanism.

The safe way to add info to a packet en-route (i.e., anywhere past the
originating upper-layer protocol) is by encapsulation, not header-insertion.

If the IPsec specs allow or encourage en-route header-insertion, they
are incompatible with the rest of the IP architecture (both versions),
and ought to be fixed.

Steve

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