PCP Deployment Models
draft-boucadair-pcp-deployment-cases-00

Abstract

This document lists a set of PCP deployment models.

Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119].

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on February 20, 2014.

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1. Introduction

This document lists a set of PCP [RFC6887] deployment models.

2. Terminology

This document makes use of the following terms:

PCP server denotes a functional element that receives and processes PCP requests from a PCP client. A PCP server can be co-located with or be separated from the function (e.g., NAT, Firewall) it controls. Refer to [RFC6887].
PCP client denotes a PCP software instance responsible for issuing PCP requests to a PCP server. Refer to [RFC6887].

3. Single Homed CPE Model: Local PCP Server

This model assumes PCP is enabled in the LAN side to control functions located in the CPE. The PCP server is reachable with the IP address of the private-faced interface.

   +-------------+
   |    PCP      |
   |   Client    |----+                           ,-----------.
   +-------------+    |   +------------+        ,'             `--.
                      +---|    CPE     |        /                   :
                          | PCP Server |_______;        ISP         |
                      +---| NAT+FW+..  |       :                    |
   +-------------+    |   +------------+        \                   |
   |    PCP      |----+                          -------------------.
   |   Client    |
   +-------------+

4. Single Homed CPE Model: Multiple PCP Servers

This model assumes a customer site is connected to the same ISP's network. One or multiple PCP servers are deployed in the ISP's domain; each of them manage distinct set of functions. In example shown in the following figure:

NAT64 device are used to interwork with IPv4-only devices.
NPTv6 function is used for engineering motivation internal to the ISP.

   +-------------+
   |    PCP      |
   |   Client    |----+                            ,-----------.
   +-------------+    |   +------------+         ,'    ISP     `--.
                      +---|    CPE     |         /                :
                          |            |________;    NAT64        |
                      +---|            |        :                 |
   +-------------+    |   +------------+         \        NPTv6   |
   |    PCP      |----+                           ----------------.
   |   Client    |
   +-------------+

Internal PCP client must discover both the external IPv4 address and port numbers assigned by the NAT64 and the external IPv6 address assigned by the NPTv6. These external addresses are used for example in referrals to indicate to remote peers both the IPv4 address and IPv6 address to reach an internal server deployed in an IPv6-only domain.

The use of anycast-based addressing model is not recommended for this deployment case because two state entries are to be created in both NAT64 and NPTv6.

The use of NAT64 and NPTv6 is for illustration purposes; other functions can be enabled.

5. Hide PCP Servers Model

5.1. PCP Proxy Model

In order to hide PCP servers deployed within an administrative domain, an administrative entity may decide to deploy in front of PCP clients PCP Proxies that are responsible for relaying PCP requests to appropriate PCP servers:

In order to prevent single failure scenarios, multiple PCP proxies can be hosted within an administrative domain.
A PCP Proxy can be configured with one or multiple servers.
Multiple PCP Proxies can be enabled; each of them manages a set of PCP servers.
A PCP Proxy can be configured with the logic indicating how it should proceed to contact upstream PCP servers.
Internal PCP clients are configured with the IP address(es) of the appropriate PCP proxy.
- If all PCP Proxies interact with the same PCP Server(s), the same IP address can be provisioned to PCP clients.
- If PCP Proxies do not interact with the same set of PCP Server(s), appropriate IP address(es) are to be returned to each requesting PCP Client.

               +------------------------------------+
               | Administrative Domain              |
+----------+   |    +-------------------+           |
|PCP Client|---|----|    PCP Proxy      |           |
+----------+   |    +-------------------+           |
               |        |            |              |
               |        |            |              |
               | +------+------+   +-+------------+ |
               | | PCP Server  |   | PCP Server   | | 
               | +-------------+   +--------------+ |  
               +------------------------------------+

5.2. HTTP-Triggered PCP Client Model

Another deployment model to hide deployed PCP servers is to relay on HTTP to interact with the PCP service. This model can also be used by operators to accommodate cases where the PCP client is not available at the customer side.

The deployment model relies on the following:

An HTTP administration based interface is provided to the user to create flow-bases forwarding rules.
The HTTP GUI can be part of a CPE management interface or be provided as part of the customer care portal.
HTTP requests are translated into appropriate PCP servers in order to install the requested state. The HTTP server embeds also a PCP client.
The PCP client uses THIRD_PARTY option.
The PCP Client should be configured with PCP server that controls the on-path PCP-controlled device for that user.
One or multiple PCP Servers can be deployed.
The use of a well-known address to reach internal PCP servers may not be convenient if all PCP server do not manage the same set of states.

               +------------------------------------+
               | Administrative Domain              |
+----------+   |    +----------------------+        |
|  Host    |---|----|HTTP Server+PCP Client|        |
+----------+   |    +----------------------+        |
               |        |            |              |
               |        |            |              |
               | +------+------+   +-+------------+ |
               | | PCP Server  |   | PCP Server   | | 
               | +-------------+   +--------------+ |  
               +------------------------------------+

6. Separated PCP Server & PCP-controlled Device Model

This model assumes the PCP server is not co-located with the PCP-controlled device. Moreover:

In order to prevent single failure scenarios, multiple PCP servers can be hosted within an administrative domain.
A PCP server can be control one or many PCP-controlled devices.
Multiple PCP servers can be enabled; each of them manages a set of PCP-controlled devices.
Internal PCP clients are configured with the IP address(es) of the appropriate PCP server.
- If all PCP servers interact with the same PCP-controlled devices., the same IP address can be provisioned to PCP clients.
- If PCP servers do not interact with the same set of PCP-controlled devices, appropriate IP address(es) are to be returned to each requesting PCP Client.

Note, PCP is not used as interface between the PCP server and the PCP-controlled device. Other protocols (e.g., H.248) can be used for that purpose.

7. Cascaded PCP-controlled Nodes Model

This model assumes cascaded PCP-controlled devices are deployed. A typical example is provided below.

                                                      ,-----------.
                               PCP Server           ,'             `--.
   +-------+    +------+      +----------+         /                   :
   |PCP    |____|Home  |______|ISP CPE   |________;     Public         |
   |Client |    |Router|      |NAT Router|        :     Internet       |
   +-------+    +------+      +----------+         \                   |
                                                    \                  ;
                                                     `------.       ,-'
                                                             `-----'
                                                      ,-----------.
                              PCP Server            ,'             `--.
   +-------+    +------+      +-------+            /                   :
   |PCP    |____|CPE   |______|CGN/FW |___________;     Public         |
   |Client |    |      |      |       |           :     Internet       |
   +-------+    +------+      +-------+            \                   |
                                                    \                  ;
                                                     `------.       ,-'
                                                             `-----'
                                                      ,-----------.
               PCP Proxy               PCP Server   ,'             `--.
   +-------+    +------+               +-------+   /                   :
   |PCP    |____|CPE   |_______________|CGN/FW |__;     Public         |
   |Client |    |      |               |       |  :     Internet       |
   +-------+    +------+               +-------+   \                   |
                                                    \                  ;
                                                     `------.       ,-'
                                                             `-----'
                                                      ,-----------.
               PCP Server              PCP Server   ,'             `--.
   +-------+    +------+               +-------+   /                   :
   |PCP    |____|CPE   |_______________|CGN/FW |__;     Public         |
   |Client |    |      |               |       |  :     Internet       |
   +-------+    +------+               +-------+   \                   |
                                                    \                  ;
                                                     `------.       ,-'
                                                             `-----'

[I-D.ietf-pcp-proxy] be deployed in intermediate PCP-controlled devices:

The PCP client is not aware of the presence of more than one level of PCP servers.
Each intermediate PCP proxy must contact the appropriate next hop PCP server.
Because of the statefull nature of PCP, anycast-based addressing model may not be appropriate when the PCP Server is co-located with the PCP-controlled device.

7.1. Single Homed CPE Model: PCP Proxy Model

This model assumes no PCP-controlled function is located in the CPE (e.g., DS-Lite case). The ultimate PCP server is located in ISP side. The PCP server can be deduced from other provisioning parameters (e.g., use the IP address of the AFTR as PCP server); otherwise the IP address (s) must be discovered by other means.

The use of an anycast-based model may not be convenient in some cases (e.g., multiple PCP-controlled devices are deployed; each of them manage a subset of services and state).

   +-------------+
   |   Host      |
   |             |----+                         ,-----------.
   +-------------+    |   +------------+      ,'             `--.
                      +---|    CPE     |      /     ISP           :
                          | PCP Proxy  |_____;    PCP Server 1    |
                      +---| PCP Client |     :    PCP Server i    |
   +-------------+    |   +------------+      \                   |
   |    PCP      |----+                        -------------------.
   |   Client    |
   +-------------+

7.2. UPnP IGD-PCP Interworking Model

This model is specified in [RFC6970]. The interworking function must be provisioned with the IP address(es) of remote PCP server(s).

(a) 
   +-------------+
   | IGD Control |
   |   Point     |----+
   +-------------+    |   +-----+  +--------+               +------+
                      +---| IGD-|  |Provider|               |Remote|
                          | PCP |--|  NAT   |--<Internet>---| Host |
                      +---| IWF |  |        |               |      |
   +-------------+    |   +-----+  +--------+               +------+
   | Local Host  |----+
   +-------------+
                        LAN Side  External Side
   <======UPnP IGD==============><=====PCP=====>

(b) 
   +-------------+
   | IGD Control |
   |   Point     |----+
   +-------------+    |   +-----+  +--------+               +------+
                      +---| IGD-|  |Provider|               |Remote|
                          | PCP |--|  NAT   |--<Internet>---| Host |
                      +---| IWF |  |        |               |      |
   +-------------+    |   +-----+  +--------+               +------+
   | Local Host  |----+    NAT1           NAT2
   +-------------+

8. Multi-Homed CPE Model: One Single PCP Server

A typical example of this model is shown in the following figure:

                     ====================
                     |    Internet       |
                     =====================
                        |              |
                        |              |
                   +----+--------+   +-+------------+
                   | ISP1        |   | ISP2         |
                   |             |   |              |
                   +----+--------+   +-+------------+  
                        |              |
                        |              |
      ..............................................................
                        |              |
                        | Port1        | Port2    Subscriber Network
                        |              |
                   +----------------------+
                   |   NAT & PCP servers  |
                   |       GW Router      |
                   +----+-----------------+
                        |
                        |
                        |
                   -----+--------------
                        |
                      +-+-----+
                      | Hosts |  (private address space)
                      +-------+

Internal PCP clients can interact with one single PCP servers.

9. Multi-Homed CPE Model: Multiple PCP Servers

A typical example of this model is shown in the following figure:

                       ==================
                       |    Internet    |
                       ==================
                          |          |
                          |          |
                     +----+-+      +-+----+
                     | ISP1 |      | ISP2 |
                     +----+-+      +-+----+       
                          |          |
    .........................................................
                          |          |
                          |          |        Subscriber Network
                  +-------+---+ +----+------+
                  | rtr1 with | | rtr2 with |
                  |   FW1     | |    FW2    |
                  +-------+---+ +----+------+
                          |          |
                          |          |
                          |          |
                   -------+----------+------
                          |
                        +-+-----+
                        | Hosts |
                        +-------+

The PCP client must interact with all PCP servers; otherwise complications arise to communicate with remote peers. The use of anycast-based model will induce failures in communicating with external peers (e.g., incoming packets will be dropped by one of the firewalls).

10. Security Considerations

PCP-related security considerations are discussed in [RFC6887].

11. IANA Considerations

This document does not require any action from IANA.

12. Acknowledgements

TBC.

13. References

13.1. Normative References

[RFC2119]	Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6887]	Wing, D., Cheshire, S., Boucadair, M., Penno, R. and P. Selkirk, "Port Control Protocol (PCP)", RFC 6887, April 2013.

13.2. Informative References

[RFC6970]	Boucadair, M., Penno, R. and D. Wing, "Universal Plug and Play (UPnP) Internet Gateway Device - Port Control Protocol Interworking Function (IGD-PCP IWF)", RFC 6970, July 2013.
[I-D.ietf-pcp-proxy]	Boucadair, M., Penno, R. and D. Wing, "Port Control Protocol (PCP) Proxy Function", Internet-Draft draft-ietf-pcp-proxy-02, February 2013.

Author's Address

Mohamed Boucadair France Telecom Rennes, 35000 France EMail: mohamed.boucadair@orange.com