| PCP Working Group | M. Boucadair |
| Internet-Draft | France Telecom |
| Intended status: Informational | April 16, 2014 |
| Expires: October 18, 2014 |
Port Control Protocol (PCP) Deployment Models
draft-boucadair-pcp-deployment-cases-02
This document lists a set of Port Control Protocol (PCP) deployment models.
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].
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This document lists a set of PCP [RFC6887] deployment models.
This document makes use of the following terms:
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 of the CPE. Typical functions that can be controlled by PCP in this model are NAT and firewall.
+-------------+
| PCP |
| Client |----+ ,-----------.
+-------------+ | +------------+ ,' `--.
+---| CPE | / :
| PCP server |_______; ISP |
+---| NAT+FW+.. | : |
+-------------+ | +------------+ \ |
| PCP |----+ -------------------.
| Client |
+-------------+
PCP client can be configured with their PCP server using DHCP for instance [I-D.ietf-pcp-dhcp]. If no PCP server is configured, PCP clients assume their default gateway is the PCP server.
This model applies for both residential or corporate markets.
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 the example shown in the following figure:
+-------------+
| PCP |
| Client |----+ ,-----------.
+-------------+ | +------------+ ,' ISP `--.
+---| CPE | / :
| |________; NAT64 |
+---| | : |
+-------------+ | +------------+ \ NPTv6 |
| PCP |----+ ----------------.
| Client |
+-------------+
The use of NAT64 and NPTv6 functions is for illustration purposes; other functions can be enabled in the ISP's network side.
PCP clients located behind the CPE, 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 a PCP anycast address ([I-D.ietf-pcp-anycast]) is not recommended for this deployment case because two state entries must be created in both NAT64 and NPTv6. Explicit means such as [I-D.ietf-pcp-dhcp] must be used instead to provision IP addresses of available PCP servers.
[I-D.ietf-pcp-dhcp] may be used to provision the IP addresses of these PCP servers, or the CPE must embed a PCP proxy function that must follow [I-D.ietf-pcp-server-selection] to contact all PCP servers.
In order to hide PCP servers deployed within an administrative domain, an administrative entity may decide to deploy one or more PCP proxies [I-D.ietf-pcp-proxy] in front of PCP clients. A PCP proxy is responsible for relaying PCP requests to the appropriate PCP server(s):
+------------------------------------+
| Administrative Domain |
+----------+ | +-------------------+ |
|PCP client|---|----| PCP proxy | |
+----------+ | +-------------------+ |
| | | |
| | | |
| +------+------+ +-+------------+ |
| | PCP server | | PCP server | |
| +-------------+ +--------------+ |
+------------------------------------+
The PCP proxy should not use the PCP anycast address ([I-D.ietf-pcp-anycast]) if available PCP servers do not manage the same PCP-controlled device. Deterministic means should be used instead.
PCP client should not use the PCP anycast address to reach a PCP proxy if deployed PCP proxies do not interact with the same PCP servers. Explicit provisioning means should be preferred.
If the PCP proxy is reachable using the PCP anycast address, available PCP servers must not be reachable using the same PCP anycast address.
Another deployment model to hide the identity of back-end PCP servers is to rely on HTTP to invoke the PCP service. This model can be used by operators to accommodate cases where a PCP client implementation is not available at the customer side (e.g., unmanaged CPE model).
The deployment model relies on the following:
+------------------------------------+
| Administrative Domain |
+----------+ | +----------------------+ |
| Host |---|----|HTTP Server+PCP client| |
+----------+ | +----------------------+ |
| | | |
| | | |
| +------+------+ +-+------------+ |
| | PCP server | | PCP server | |
| +-------------+ +--------------+ |
+------------------------------------+
This model assumes the PCP server is not co-located with the PCP-controlled device. Moreover:
Note, PCP is not used between the PCP server and the PCP-controlled device. Other protocols (e.g., H.248) can be used for that purpose.
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:
This model assumes no PCP-controlled function is located in the CPE (e.g., DS-Lite case). The upstream PCP server is located in the ISP's network. 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 |
+-------------+
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
+-------------+
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 server.
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 procedure defined in [I-D.ietf-pcp-server-selection] is used to contact those servers.
The use of anycast-based model ([I-D.ietf-pcp-anycast]) might induce failures when communicating with external peers (e.g., incoming packets will be dropped by one of the firewalls).
PCP-related security considerations are discussed in [RFC6887].
This document does not require any action from IANA.
| [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. |