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Re: [BEHAVE] Fwd: IPv6 hosts sending <1280 byte packets

Iljitsch van Beijnum <iljitsch@muada.com> Tue, 09 February 2010 18:49 UTC

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From: Iljitsch van Beijnum <iljitsch@muada.com>
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To: "Templin, Fred L" <Fred.L.Templin@boeing.com>
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Cc: "behave@ietf.org" <behave@ietf.org>, Dan Wing <dwing@cisco.com>
Subject: Re: [BEHAVE] Fwd: IPv6 hosts sending <1280 byte packets
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On 9 feb 2010, at 19:34, Templin, Fred L wrote:

> You may be missing the "dumbbell configutation" where
> both the IPv6 host and translator are on 9KB links but
> there are 1500 links in between?

Yes, that could happen. And it would suck.  :-)

For the IPv6-to-IPv4 direction there is no problem, because the IPv6 host simply runs PMTUD. For the IPv4-to-IPv6 direction with DF=1 any black holes on the IPv4 side will be triggered and with DF=0 I believe the current text specifies always fragmenting to 1280, which I very much disagree with and which we haven't had any discussion about.

But you really don't want to run a translator with jumboframes if you can't reach at least _some_ translator clients with large packets.

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