RFC 2460, "Internet Protocol, Version 6 (IPv6) Specification", December 1998
Note: This RFC has been obsoleted by RFC 8200Source of RFC: ipngwg (int)
Errata ID: 2843
Reported By: Florian Weimer
Date Reported: 2011-06-24
Rejected by: Brian Haberman
Date Rejected: 2012-06-01
Section 5 says:
In response to an IPv6 packet that is sent to an IPv4 destination (i.e., a packet that undergoes translation from IPv6 to IPv4), the originating IPv6 node may receive an ICMP Packet Too Big message reporting a Next-Hop MTU less than 1280. In that case, the IPv6 node is not required to reduce the size of subsequent packets to less than 1280, but must include a Fragment header in those packets so that the IPv6-to-IPv4 translating router can obtain a suitable Identification value to use in resulting IPv4 fragments. Note that this means the payload may have to be reduced to 1232 octets (1280 minus 40 for the IPv6 header and 8 for the Fragment header), and smaller still if additional extension headers are used.
It should say:
This requirement makes it impossible to offer services over IPv6 without keeping per-flow state in the server node. There is no reason why IPv4 fragmentation cannot be used after translation to IPv4.
This would be a fundamental change to the IPv6 protocol specification. Such a proposal would need to be formally proposed as an internet draft.