RADIUS Extensions for Port Control Protocol
draft-maglione-pcp-radius-ext-00

Abstract

Port Control Protocol (PCP) provides a mechanism to pre-configure a port on a NAT device, a firewall, etc., so that IP packets of applications initiated from network side can be “port forwarded” to the correct user. PCP is a client-server protocol and the PCP client needs to be provisioned with the FQDN of the server. In a broadband network, customer information is usually stored on a RADIUS server and DHC protocol is used to populate user’s configuration information. This memo proposes a new RADIUS attribute to carry the FQDN of a PCP server, such that while the PCP server information is configured on a RADIUS server, the information can be conveyed to NAS via RADIUS protocol, and the co-located DHCP/DHCPv6 server can then populate the information to PCP client.

Status of this Memo

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Table of Contents

1.  Introduction
2.  Terminology
3.  PCP Server Configuration using RADIUS and DHCP/DHCPv6
4.  RADIUS Attribute
5.  Table of attributes
6.  Security Considerations
7.  IANA Considerations
8.  Normative References
§  Authors' Addresses

1.  Introduction

Port Control Protocol (PCP) [I‑D.ietf‑pcp‑base] (Wing, D., “Port Control Protocol (PCP),” January 2011.) provides a mechanism to control how incoming packets are forwarded by upstream devices such as NATs and firewalls. PCP is a client-server protocol where a PCP client may reside on a host, a CPE, etc., which communicates with a PCP server that may reside anywhere in a network.

A PCP client must know the Fully Qualified Domain Name of a PCP server, before it can communicate with the later in order to perform the relevant functions defined by PCP.

The draft [I‑D.bpw‑pcp‑dhcp] (Boucadair, M., Penno, R., and D. Wing, “DHCP and DHCPv6 Options for Port Control Protocol (PCP),” October 2010.) defines DHCPv6 and DHCP options which are meant to be used by a PCP client to discover a PCP server name. However, provisioning for name of the PCP server is required on a DHCP/DHCPv6 server before it can populate these information.

Auto-configuration on a DHCP/DHCPv6 is possible in a broadband network, where typically, user profile is maintained on a RADIUS server and RADIUS protocol [RFC2865] (Rigney, C., Willens, S., Rubens, A., and W. Simpson, “Remote Authentication Dial In User Service (RADIUS),” June 2000.) is used to convey user related information to other network elements including a host and CPE. [I‑D.ietf‑radext‑ipv6‑access] (Lourdelet, B., Dec, W., Sarikaya, B., Zorn, G., and D. Miles, “RADIUS attributes for IPv6 Access Networks,” July 2010.) describes a typical broadband network scenario in which the Network Access Server (NAS) acts as the access gateway for the users (hosts or CPEs) and the NAS embeds a DHCPv6 Server function that allows it to locally handle any DHCPv6 requests issued by the clients.

In such environment, PCP server’s name can be configured on a RADIUS server, which then passes the information to a NAS that co-locates with the DHCP/DHCPv6 server, which in turn populates the location of the PCP server.

This memo defines a new RADIUS attribute that can be used to carry the FQDN of a PCP server.

2.  Terminology

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 [RFC2119] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).

The following terms are defined in [I‑D.ietf‑pcp‑base] (Wing, D., “Port Control Protocol (PCP),” January 2011.):

- Port forwarding

- PCP

- PCP client

- PCP Server

3.  PCP Server Configuration using RADIUS and DHCP/DHCPv6

Figure 1 (RADIUS and DHCPv6 Message Flow for a PPP Session) illustrates how RADIUS protocol works together with DHCPv6, to allow a user (host or CPE) to learn automatically the FQDN of a PCP server in case of a PPP Session that carries IPv6 traffic.

The Network Access Server (NAS) operates as a client of RADIUS and as DHCPv6 Server for DHCPv6 protocol. The NAS initially sends a RADIUS Access Request message to the RADIUS server, requesting authentication. Once the RADIUS server receives the request, it validates the sending client and if the request is approved, the RADIUS server replies with an Access Accept message including a list of attribute-value pairs that describe the parameters to be used for this session. This list may also contain the name of a PCP server. When the NAS receives a DHCPv6 message containing the PCP Server Option, the NAS shall use the name returned in the RADIUS attribute as defined in this memo to populate the DHCPv6 PCP Server option defined in [I‑D.bpw‑pcp‑dhcp] (Boucadair, M., Penno, R., and D. Wing, “DHCP and DHCPv6 Options for Port Control Protocol (PCP),” October 2010.)

   PCP                                NAS                     AAA
  Client                               |                     Server
    |                                  |                        |
    |----PPP LCP Config Request------> |                        |
    |                                  |                        |
    |                                  |----Access-Request ---->|
    |                                  |                        |
    |                                  |<-Access-Accept---------|
    |                                  | (PCP-server-name)      |
    |<-----PPP LCP Config ACK  -----   |                        |
    |                                  |                        |
    |                                  |                        |
    |------ PPP IPv6CP Config Req ---->|                        |
    |                                  |                        |
    |<----- PPP IPv6CP Config ACK -----|                        |
    |                                  |                        |
    |-------  DHCPv6 Solicit  -------->|                        |
    |                                  |                        |
    |<-------DHCPv6 Advertisement------|                        |
    |  (PCP server FQDN DHCPv6 Option) |                        |
    |                                  |                        |
    |-------  DHCPv6 Request  -------->|                        |
    |  (PCP server FQDN DHCPv6 Option) |                        |
    |                                  |                        |
    |<-------- DHCPv6 Reply ---------  |                        |
    |  (PCP server FQDN DHCPv6 Option) |                        |
    |                                  |                        |

                DHCPv6                         RADIUS

The Figure 2 (RADIUS and DHCPv6 Message Flow for an IP Session) illustrates how the RADIUS protocol and DHCPv6 work together to accomplish PCP client configuration when an IP Session is used to provide connectivity to the user.

The only difference between this message flow and previous one is that in this scenario the interaction between NAS and AAA/ RADIUS Server is triggered by the DHCPv6 Solicit message received by the NAS from the B4 acting as DHCPv6 client, while in case of a PPP Session the trigger is the PPP LCP Config Request message received by the NAS.

    PC                                NAS                     AAA
  Client                               |                     Server
    |                                  |                        |
    |------ DHCPv6 Solicit --------->  |                        |
    |                                  |                        |
    |                                  |----Access-Request ---->|
    |                                  |                        |
    |                                  |<-Access-Accept---------|
    |                                  | (PCP-server-name)      |
    |                                  |                        |
    |<-------DHCPv6 Advertisement------|                        |
    |  (PCP server FQDN DHCPv6 Option) |                        |
    |                                  |                        |
    |-------  DHCPv6 Request  -------->|                        |
    |  (PCP server FQDN DHCPv6 Option) |                        |
    |                                  |                        |
    | <-------- DHCPv6 Reply --------- |                        |
    | (PCP server FQDN DHCPv6 Option)  |                        |


                DHCPv6                         RADIUS

A similar message flow also applies to the IPv4 scenario when an IP Session is used to provide connectivity to the user (Figure 3 (RADIUS and DHCPv4 Message Flow for an IP Session)).

    PC                                NAS                     AAA
  Client                               |                     Server
    |                                  |                        |
    |-------- DHCP Discovery --------> |                        |
    |                                  |                        |
    |                                  |----Access-Request ---->|
    |                                  |                        |
    |                                  |<-Access-Accept---------|
    |                                  | (PCP-server-name)      |
    |                                  |                        |
    |<--------- DHCP Offer ------------|                        |
    |    (PCP server FQDN Sub-Option)  |                        |
    |                                  |                        |
    |---------  DHCP Request  -------->|                        |
    |   (PCP server FQDN Sub-Option)   |                        |
    |                                  |                        |
    | <--------- DHCP Ack -------------|                        |
    |    (PCP server FQDN Sub-Option)  |                        |

                DHCPv4                         RADIUS

The scenario with PPP Session and IPv4 only connectivity does not require the DHCP protocol: the whole configuration of the client is performed by PPP. This case is out of scope of this document because in order to complete the configuration of the PCP client a new PPP IPC option would be required.

4.  RADIUS Attribute

A new RADIUS attribute, called PCP-Server-Name, along with its format is defined below.

Description

The PCP-server-name attribute contains a Fully Qualified Domain Name (FQDN) that refers to a PCP server the client requests to establish a connection to for PCP related service. The NAS shall use the name returned in the RADIUS PCP-server-name attribute to populate the PCP Server FQDN DHCP Sub-Option in IPv4 addressing context, or the PCP Server FQDN DHCPv6 Option in IPv6 addressing context, as determined by the DHCP server [I‑D.bpw‑pcp‑dhcp] (Boucadair, M., Penno, R., and D. Wing, “DHCP and DHCPv6 Options for Port Control Protocol (PCP),” October 2010.)

The PCP-server-name attribute MAY appear in an Access-Accept packet, and may also appear in an Accounting-Request packet. In either case, the attribute MUST NOT appear more than once in a single packet. The PCP-server-name MUST NOT appear in any other RADIUS packets.

A summary of the PCP-Server-Name RADIUS attribute format is shown below. The fields are transmitted from left to right.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |  PCP-Server-Name (FQDN)       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                PCP-Server-Name (FQDN) (cont)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Type:

TBA1 for PCP-Server-Name.

Length:

This field indicates the total length in octets of this attribute including the Type, the Length fields and the length in octets of the PCP-Server-Name field

PCP-Server-Name:

A single Fully Qualified Domain Name of the PCP-Server. The domain name is encoded as specified in [RFC1035] (Mockapetris, P., “Domain names - implementation and specification,” November 1987.)

5.  Table of attributes

The following table provides a guide to which attributes may be found in which kinds of packets, and in what quantity.

The following table defines the meaning of the above table entries.

6.  Security Considerations

This document has no additional security considerations beyond those already identified in [RFC2865] (Rigney, C., Willens, S., Rubens, A., and W. Simpson, “Remote Authentication Dial In User Service (RADIUS),” June 2000.).

7.  IANA Considerations

This document requests the allocation of a new Radius attribute types from the IANA registry "Radius Attribute Types" located at http://www.iana.org/assignments/radius-types

PCP-Server-Name - TBA1

8. Normative References

Authors' Addresses