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

[Joe Touch <[e-mail]>]

Some further points...

On 6/1/2012 7:45 PM, Masataka Ohta wrote:
> Joe Touch wrote:
> 
>>> Existing routers, which was relying on ID uniqueness of atomic
>>> packets, are now broken when they fragment the atomic packets.
> 
>> The recommendation in this doc - that such sources MUST rate-limit - is
>> to comply with the ID uniqueness requirements already in RFC791 that
>> this doc does not deprecate - e.g., its use to support fragmentation.
> 
> It means that the uniqueness requirements must be loosened.

This document does that for atomic datagrams. We discussed whether it
was realistic to change the requirements for non-atomic datagrams in
INTAREA, and decided it wasn't.

> Another example is that, when route changes, routers
> fragmenting atomic packets may change, which means rate
> limiting does not guarantee ID uniqueness.

Rate limiting (of non-atomic datagrams) is at the source, which ensures
ID uniqueness regardless of where they are fragmented.

Routers already should not be fragmenting atomic datagrams, as has been
noted.

Joe