Subject: [Softwires] Per-interface NAT in mobile networks

From: <[email-masked]>
Date: Mon, 25 Oct 2010 16:47:03 +0200

Dear all,

   When per-interface NAT is applied to 3GPP networks, a NAT function
   can be embedded in the GGSN/PGW.  The GTP tunnel identifier will be
   used as an identifier in the NAT table to identify sessions belonging
   to each UE.  Packets are then translated and forwarded to their
   destination (either internal or external).  Distinct IPv4 address
   pools may be configured on the GGSN/PGW depending on the APN.  This
   procedure can be implemented in mono stack PDP context or in
   dual stack PDP contexts.

   Embedding a NAT in the PGW/GGSN is one of the scenarios we are
   considering to rationalise the use of IPv4 address in mobile
   networks, while promoting the invocation of IPv6 transfer
   capabilities whenever possible (our recommendation for mobile is to
   go for dual-stack connectivity).  Unlike other solutions where the
   NAT is not embedded in the PGW, the activation of the per-interface
   NAT does not impact the network availability since no new nodes will
   be introduced to embed the NAT function.

   We think per-interface NAT
   (http://datatracker.ietf.org/doc/draft-arkko-dual-stack-extra-lite/ or
   http://tools.ietf.org/html/draft-miles-behave-l2nat-00)
   is a good place to describe this use case.

   Some vendors already support a NAT function in their PGW products,
   but for harmonising the behaviour of such implementations we think it
   would be valuable to see draft-arkko-dual-stack-extra-lite be adopted
   as a WG document in Behave or Softwire.

   Is there any plan to see this I-D progress as Softwire or Behave WG
   document?

   Cheers,

   Med

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From: Jari Arkko <[email-masked]>
Date: Mon, 25 Oct 2010 18:22:32 +0300

Mohamed,

Thanks for your interest on this!

For everyone's information: I have asked the document to be AD sponsored 
through to the IETF to become an RFC. I think Ralph was willing to do 
it, AD reviews and so on still obviously pending. So there may not be a 
need to adopt it at the working group. Review comments would be highly 
appreciated from everyone, of course.

Mohamed: were you thinking that we should have a also some more mobile 
network specific guidance about this? Perhaps that could be a separate 
draft (or even a 3GPP spec). I have been trying to keep my draft at the 
general level. But I do know that there are people who want to use it 
different circumstances, and some of those may benefit from additional 
specification. I know of at least one such case already, maybe yours is 
a second one.

Jari

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From: <[email-masked]>
Date: Mon, 25 Oct 2010 17:42:53 +0200

Dear Jari,

   Thank you for this feedback.  AD sponsored track is also a good path for
   this I-D.

   I don't think there is a need for another I-D to explain the usage of
   the per-interface NAT in mobile networks.  Adding a sentence to the
   draft to mention the mobile use case would be IMHO sufficient.

   Impacts of activating per-interface in PGW should be identified and
   documented by 3GPP if required.  

   Cheers,
   Med

PS: FWIW, Orange has submitted a CR to 3GPP on the
   per-interface NAT available at http://ftp.3gpp.org/tsg_sa/WG2_Arch/
   TSGS2_81_Prague/Docs/S2-104928.zip.

-----Message d'origine-----
De : Jari Arkko [mailto:[email-masked]] 
Envoyé : lundi 25 octobre 2010 17:23
À : BOUCADAIR Mohamed NCPI/NAD/TIP
Cc : Softwires list; Behave WG; [email-masked]; BINET David NCPI/NAD/TIP; BERNIER Olivier RD-CORE; IBRAHIM Houmed RD-CORE; MOUQUET Antoine RD-CORE
Objet : Re: Per-interface NAT in mobile networks

Mohamed,

Jari