Re: [homenet] DNCP/HNCP Revisited

Juliusz Chroboczek <jch@irif.fr> Wed, 18 September 2019 23:02 UTC

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Date: Thu, 19 Sep 2019 01:02:33 +0200
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From: Juliusz Chroboczek <jch@irif.fr>
To: Ted Lemon <mellon@fugue.com>
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Subject: Re: [homenet] DNCP/HNCP Revisited
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> The problem is, how’d the packet get so big that it was fragmented?

HNCP relies on network-layer fragmentation: it uses UDP and has no
application-layer mechanism for fragmenting large TLVs.  See Section 4.2
and Appendix B.2 of RFC 7787.

(I seem to recall that an earlier version of DNCP included provisions for
application-layer fragmentation of TLVs, but that was removed at some
point.  I don't remember why.)

Let's please come back to my question.  RFC 4443 paragraph 3.2 says

   A Packet Too Big MUST be sent by a router in response to a packet
   that it cannot forward because the packet is larger than the MTU of
   the outgoing link.

If your tunnelling software violates this, how is it not buggy?

-- Juliusz