* Florian Weimer

>> And I see no functional difference between the gateway and the host
>> generating the fragment ID, except that the latter approach seems to
>> require network-wide software updates currently.

A stateless translator does not keep track of the PMTU for the IPv4
destinations. That means that for it to work, it would have to clear the
Don't Fragment flag and generate a Fragment ID for every single packet
it translates to IPv4 that ends up smaller than 1260 bytes. I don't
believe this is desirable.

Also, RFC 2460 would have to be amended in order to allow hosts to
outright ignore ICMPv6 PTB w/MTU<1280, and the IPv6 host stacks would
also have to be updated accordingly. It seems to me, therefore, that the
approach of having the translator generate the Fragment ID is the one
that requires the most network-wide software updates.

* Fernando Gont

> Namely, are you saying that Linux won't react to an ICMPv6 PTB<1280 by
> inserting a Fragment Header in subsequent packets, or what? (last time I
> checked, I think this was the case)

I can confirm that Linux will react to an ICMPv6 PTB<1280 by including a
Fragment header. There are a couple of bugs in its implementation, but I
expect these to be fixed shortly (patches are already available).

https://bugzilla.kernel.org/show_bug.cgi?id=42572
https://bugzilla.kernel.org/show_bug.cgi?id=42595

-- 
Tore Anderson
Redpill Linpro AS - http://www.redpill-linpro.com
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