Re: [pcp] draft-ietf-pcp-proxy and draft-cheshire-recursive-pcp

[<[e-mail]>]

Hi Dan, 

The main reasons why we had that text are as follows:

* The PCP Proxy won't need to inspect every incoming packet. The current approach makes it easy to redirect PCP responses to the PCP proxy because PCP responses will be explicitly sent to its external IP address. 

* In some scenarios, the address family of the internal IP address is not the same as the one available in the external interface of the PCP Proxy. A typical example is DS-Lite. As you know DS-Lite assumes plain IPv6 mode, internal PCP requests are received over IPv4 while external requests are sent over IPv6 without requiring in NAT. In such case, internal request cannot just be relayed to the next PCP server.

Cheers,
Med  

>-----Message d'origine-----
>De : [e-mail] [mailto:[e-mail]] De la part de Dan
>Wing
>Envoyé : mercredi 24 juillet 2013 03:41
>À : [e-mail]
>Objet : [pcp] draft-ietf-pcp-proxy and draft-cheshire-recursive-pcp
>
>I am trying to understand the difference between draft-ietf-pcp-proxy and
>draft-cheshire-recursive-pcp.   One of the significant differences seems to
>be if the proxy should function differently from an endpoint.  draft-ietf-
>pcp-proxy has a proxy operating differently from an endpoint with the
>sentence starting with "Nevertheless"
>
>   6.  No NAT is Co-located with the PCP Proxy
>
>   When no NAT is co-located with the PCP Proxy, the port numbers
>   included in received PCP messages (from the PCP server or PCP
>   client(s)) are not altered by the PCP Proxy.  Nevertheless, the PCP
>   client IP Address MUST be changed to the address of the PCP Proxy and
>   a THIRD_PARTY Option inserted to carry the IP address of the source
>   PCP client.
>
>The text is under-specified (as the PCP proxy can have have several
>addresses, even if it is a firewall), but I don't know why the PCP proxy
>needs to add the THIRD_PARTY option.  It could just send the packet as-is,
>with the original source IP address.  The proxy will see the response just
>as it will see the TCP SYNACK response to a TCP SYN.
>
>WG thoughts?
>
>-d
>
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