Re: [pcp] PREFIX64 PCP Option for NAT64: draft-boucadair-pcp-nat64-prefix64-option

[<[e-mail]>]

Hi Simon,

Before answering your questions, I would like to say some words about the context of this work: In fact we have ported a SIP UA implementation to be PCP-aware and tested it IPv6-only environment + NAT64 in using both Wifi and 3G connectivity. The challenge was 

(1) to place successful communications between IPvx/IPvy UAs without requiring any particular mechanism in the SIP Proxy Server and ALG in the NAT64
(2) use PCP to control the NAT64

IPv6-only UA needs to be provisioned with the PREFIX64 used by the PCP-controlled NAT64 for local synthesis of IPv4-embedded IPv6 addresses. 

Retrieving the PREFIX64 used by the PCP-controlled NAT64 using PCP was a natural approach rather than mandating to support a dedicated DHCP option; mainly for the following reasons:

* DHCPv6 is not supported by some mobile UEs
* We need to correlate a PREFIX64 and a NAT64 device

Below some answers.

Cheers,
Med
 

>-----Message d'origine-----
>De : [e-mail] [mailto:[e-mail]] De la 
>part de Simon Perreault
>Envoyé : jeudi 6 septembre 2012 14:36
>À : [e-mail]
>Objet : Re: [pcp] PREFIX64 PCP Option for NAT64: 
>draft-boucadair-pcp-nat64-prefix64-option
>
>Interesting... I have a question:
>
>Consider a PCP client that receives a MAP response containing 
>a PREFIX64 
>option. Does the option apply a) only to the mapping contained in the 
>MAP response, or b) to all future mappings as well?

Med: I'm tempted to say the prefix will be used for all mappings associated with the same PCP server. A record to associate a PCP server and a PREFIX64 should be maintained by the client. We need to check if there are scenarios where the same PCP Server controls NAT64s configured with distinct PREFIX64 servicing the same IPv6-only host.  

>
>If a), how is PREFIX64 of any use to the client?

Med: I'm not sure I get your question; but PREFIX64 will be used whenever needed to construct IPv4-embedded IPv6 addresses. This is needed particularly for services which does not involve DNS64.

>
>If b), why include it in a MAP response? Why not DHCP or 
>something else? 

Med: You can include it in DHCP but for mobile terminal not supporting DHCPv6 this may not help.

>What happens if the client receives two MAP responses with conflicting 
>PREFIX64 options? Does it have to check that?

Med:  If we assume a PCP Server controls only one NAT64/PREFIX64, then it is safe the client to check whether only one PREFIX64 is learned for each PCP Server.

>
>Simon
>-- 
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