Issue 19 of draft-ietf-ipv6-node-requirements-05.txt

[Thomas Narten <narten@us.ibm.com>]

john.loughney@nokia.com writes:


> > >    Nodes MUST always be able to receive fragment headers. However, if it
> > >    does not implement path MTU discovery it may not need to send
> > >    fragment headers.  However, nodes that do not implement transmission
> > >    of fragment headers need to impose a limitation to the payload size
> > >    of layer 4 protocols.
> >      
> > This would seem inconsistent with the following wording in RFC 2460:
> > 
> >     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.

> So, this should be changed to:

> 	Nodes MUST always be able to send and receive fragment headers. (rest of
> 	the text deleted)

how about:

 	Nodes MUST always be able to send and receive fragment
 	headers. Note that even in the case where a sender does not
 	implement or use Path MTU discovery [RFC 1981], the sender
 	must still be prepared to send fragment headers, even for
 	packets that are smaller than the minimal IPv6 link MTU of
 	1280 octets. See Section 5 of [RFC 2460] for details.

Thomas	

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