Re: [v4tov6transition] IPv6 VPNs configured over 1280 MTU tunnels

Rémi Després <remi.despres@free.fr> Mon, 11 October 2010 17:03 UTC

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To: "Templin, Fred L" <Fred.L.Templin@boeing.com>
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Subject: Re: [v4tov6transition] IPv6 VPNs configured over 1280 MTU tunnels
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Le 11 oct. 2010 à 18:42, Templin, Fred L a écrit :

>> ...
>> Actually, the 6a44 specification should, instead of 1280, 
>> require IPv4 MTU - 28 octets, both for hairpinning and 
>> traversal cases.
> 
> How can you be sure that IPv4 PMTUD will work in
> the traversal case?

In the to-host direction, because the ISP network is all what is left to traverse before reaching the CPE.

In the from host direction, one can't be sure, but doesnt' need to.
If a smaller PMTU is encountered further downstream, a PTB ICMPv6 error message will be returned from there.

RD