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

Joe Touch <touch@isi.edu> Wed, 06 June 2012 00:59 UTC

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Date: Tue, 05 Jun 2012 17:58:59 -0700
From: Joe Touch <touch@isi.edu>
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To: Masataka Ohta <mohta@necom830.hpcl.titech.ac.jp>
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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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