Subject: FW: 6PE Path MTU Discovery

From: "Maglione Roberta" <[email-masked]>
Date: Tue, 20 Feb 2007 12:35:25 +0100

Re-sending because I didn't see the original mail on the mailing list...
Sorry for double posting.

Roberta

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Roberta Maglione
Telecom Italia - Broadband Network Services Innovation
Via G. Reiss Romoli, 274 - 10148 Torino - Italy
Phone: +39 011 228 5007
e-mail: [email-masked]
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-----Original Message-----
From: Invernizzi Fabrizio 
Sent: Friday, February 16, 2007 10:40 AM
To: [email-masked]'
Cc: Maglione Roberta
Subject: 6PE Path MTU Discovery

Hi all

we are currently investiganting on the deployment impacts of the 6PE
solution as described in the recently published RFC4798 (Connecting IPv6
Islands over IPv4 MPLS Using IPv6 Provider Edge Routers (6PE)) and we
have some doubts about the IPv6 Path MTU discovery mechanism traversal
of a MPLS cloud described in the RFC.
In particular the section 3 says: 
"... , routers in the IPv4 MPLS network have the option to
   generate an ICMP "Packet Too Big" message using mechanisms as
   described in section 2.3.2 "Tunneling Private Addresses through a
   Public Backbone" of [RFC3032]."

What is not clear to us is:
1- how can a P router, IPv4 only, generate an IPv6 icmp message (for
example, which source addres should it use?)
2- does this imply enabling IPv6 on all the MPLS network? If yes, is
correct to say that this would reduce the benefits of using the 6PE
solution? (no changes required on the MPLS network and IPv6 enabled only
on the "edge" routers, the 6PEs)

Would be interesting for this community to investigate a mechanism to
make the 6PE routers able to dynamically discover the PMTU for each LSP
to be used to transport the IPv6 packets through the MPLS network(may be
leveraging on the native MPLS PMTU discovery mechanism?)
If yes, we are available to cohoperate to produce a proposal on this
topic.

Thanks in advance

Roberta and Fabrizio
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