Re: Last Call: <draft-ietf-intarea-ipv4-id-update-05.txt> (Updated Specification of the IPv4 ID Field) to Proposed Standard

Masataka Ohta <> Thu, 21 June 2012 00:58 UTC

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Date: Thu, 21 Jun 2012 09:57:00 +0900
From: Masataka Ohta <>
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Subject: Re: Last Call: <draft-ietf-intarea-ipv4-id-update-05.txt> (Updated Specification of the IPv4 ID Field) to Proposed Standard
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Though the ID states:

   document underscores the point that not only is reassembly (and
   possibly subsequent fragmentation) required for translation, it can
   be used to avoid issues with IPv4 ID uniqueness.

according to RFC2765, which does not need port numbers for
address mapping:

   If the IPv6 packet contains a Fragment header the header fields are
   set as above with the following exceptions:

                 Copied from the low-order 16-bits in the
                 Identification field in the Fragment header.

                 The More Fragments flag is copied from the M flag in
                 the Fragment header.  The Don't Fragments flag is set
                 to zero allowing this packet to be fragmented by IPv4

the translated IPv4 packets are not atomic with 16bit IDs.

Note that the RFC is referred by NAT646 etc.

Then, aren't IPv6 nodes are required to rate limit packets
they generate with fragment headers assuming 16bit IDs?

Or, are 6 to 4 translators are required to rate limit and
drop rate-violating packets to make the "stateless"
translators full of states.


						Masataka Ohta


As the RFC specifies ID=0 when DF is set 0, it should also
be updated to conform to the robustness principle.