Subject: [pcp] -06 review: ds-lite

From: Paul Selkirk <[email-masked]>
Date: Tue, 08 Mar 2011 04:26:00 +0000

12.1.1 (DS-Lite overview) is written oddly - if you miss (or mis-read)
the first sentence, you'd conclude that these are requirements for all
B4 elements.

   Various PCP deployment scenarios can be considered to control the PCP
   server embedded in the AFTR element:

   1.  UPnP IGD and NAT-PMP [I-D.cheshire-nat-pmp] are used in the LAN:
       an interworking function is required to be embedded in the B4
       element to ensure interworking between the protocol used in the
       LAN and PCP.  UPnP IGD-PCP Interworking Function is described in
       [I-D.bpw-pcp-upnp-igd-interworking].

This needs to mention NAT-PMP IWF, even if there isn't a doc to refer
to yet.

   2.  Hosts behind the B4 element will either include a PCP client or
       UPnP IGD client, or both.

       A.  if a UPnP IGD client, the B4 element will need to include an
           interworking function from UPnP IGD to PCP.

       B.  if a PCP client, the PCP client will communicate directly
           with the PCP server.

I don't understand the difference between 2a and 1.

   3.  The B4 element includes a PCP client which is invoked by an HTTP-
       based configuration (as is common today).  The internal IP
       address field in the PCP payload would be the internal host used
       in the port forwarding configuration.

The parenthetical comment implies (or could be read as implying) that a
B4 PCP client is common today.

That notwithstanding, current HTTP-based configuration of a home gateway
creates static mappings, which PCP can't do.  So this requires a
UPnP-like IWF, with automatic and indefinite renewals.

Also, s/PCP payload/THIRD_PARTY Option/

   In Dual Stack-Lite, the B4 element encapsulates its PCP messages into
   the IPv6 tunnel towards the AFTR element.  It is expected the B4
   element will also perform as a proxy from PCP to PCP
   [I-D.bpw-pcp-proxy], and may also proxy from other protocols to PCP
   (e.g., [I-D.bpw-pcp-upnp-igd-interworking].  When proxying for other
   hosts, the B4 element will necessarily use the THIRD_PARTY option
   with the MAP and PEER OpCodes.

At this point in time, the B4 element SHOULD include UPnP-IGD IWF, and
MAY include NAT-PMP IWF.  Depending on the PCP discovery mechanism, PCP
clients in hosts behind the B4 MAY send PCP requests to the B4 (as the
default router), in which the B4 will have to proxy the PCP requests
to the AFTR; or they MAY send PCP requests directly to the AFTR
(e.g. to 192.0.0.1), in which case the B4 will encapsulate the
requests as ordinary IPv4 traffic over the IPv6 tunnel.

				paul