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Re: New Version Notification for draft-bonica-6man-frag-deprecate-00.txt

"Fred Baker (fred)" <fred@cisco.com> Sun, 23 June 2013 23:12 UTC

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From: "Fred Baker (fred)" <fred@cisco.com>
To: Tore Anderson <tore@fud.no>
Subject: Re: New Version Notification for draft-bonica-6man-frag-deprecate-00.txt
Thread-Topic: New Version Notification for draft-bonica-6man-frag-deprecate-00.txt
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Date: Sun, 23 Jun 2013 23:11:57 +0000
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On Jun 22, 2013, at 2:29 AM, Tore Anderson <tore@fud.no> wrote:
> - When a SIIT translator receives an IPv4 packet with DF=0 that would
> result in an IPv6 packet that would exceed the IPv6 link MTU, it will
> split the original packet into IPv6 fragments.

It *could* fragment the IPv4 packet and send it in two unfragmented IPv6 packets.

> I cannot support your draft until it discusses or provides solutions for
> the above considerations.

I'm in a similar case with respect to protocols above IPv6 (OSPF and NFS/UDP come quickly to mind) that depend on fragmentation to deal with the issue. I think the Robustness Principle tells us that such applications SHOULD figure out how to live with PMTU, but it also tells us that we can't deprecate fragmentation unless all known instances that depend on it have defined practical work-arounds. I suspect that this would imply the re-creation of the fragmentation feature in an intermediate protocol, which seems like a lot of work with little real gain.

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