This document specifies DHCP (IPv4 and IPv6) options to configure hosts with Port Control Protocol (PCP) Server IP addresses. The use of DHCPv4 or DHCPv6 depends on the PCP deployment scenario.

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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1. Introduction

This document defines DHCPv4 [RFC2131] and DHCPv6 [RFC3315] options that can be used to provision PCP server [RFC6887] IP addresses.

This specification assumes a PCP server is reachable with one or multiple IP addresses. As such, a list of IP addresses can be returned in the PCP server DHCP option.

This specification allows to return one or multiple instances of the PCP server DHCP option. This is used as a hint to guide the PCP client whether it needs to send PCP requests to one or multiple PCP servers.

When multiple instances of the PCP server DHCP option or multiple IP addresses are received from the DHCP server, the PCP client follows the behavior specified in [I-D.ietf-pcp-server-selection].

2. Terminology

3. DHCPv6 PCP Server Option

3.1. Format

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      OPTION_PCP_SERVER        |         Option-length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                         ipv6-address                          |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                         ipv6-address                          |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 1: PCP Server DHCPv6 Option

Option-code: OPTION_PCP_SERVER (TBA, see Section 9.1)
Option-length: Length of the 'PCP server IP Address(es)' field in octets. MUST be a multiple of 16.
PCP server IPv6 Address(es): Includes one or more IPv6 addresses [RFC4291] of the PCP server(s) to be used by the PCP client. Note, IPv4-mapped IPv6 addresses (Section 2.5.5.2 of [RFC4291]) are allowed to be included in this option.

3.2. Client Behavior

To discover a PCP server [RFC6887], the DHCPv6 client MUST include an Option Request Option (ORO) requesting the DHCPv6 PCP server option as described in Section 22.7 of [RFC3315] (i.e., include OPTION_PCP_SERVER on its OPTION_ORO).

The client MUST be prepared to receive multiple instances of the DHCPv6 PCP server option; each instance is treated as a separate PCP server.

The client MUST be prepared to receive one or multiple IPv6 addresses in the same PCP server option.

If an IPv4-mapped IPv6 address is received in an OPTION_PCP_SERVER option, the PCP client issues IPv4 PCP messages to that PCP server. This behavior is compliant with the behavior of Windows and Mac OS as reported in Section 4.2 of [RFC6052].

When multiple instances of the PCP server DHCPv6 option or multiple IPv6 addresses are received from the DHCPv6 server, the PCP client follows the behavior specified in [I-D.ietf-pcp-server-selection].

4. DHCPv4 PCP Option

4.1. Format

The PCP server DHCPv4 option can be used to configure a list of IPv4 addresses to be used by the PCP client to contact the PCP server. The format of this option is illustrated in Figure 2.

    Code   Len   PCP server IPv4 Address  PCP server IPv4 Address
   +-----+-----+-----+-----+-----+-----+-----+-----+--
   | TBA |  n  |  a1 |  a2 |  a3 |  a4 |  a1 |  a2 | ...
   +-----+-----+-----+-----+-----+-----+-----+-----+--

This format assumes that an IPv4 address is encoded as a1.a2.a3.a4.

Figure 2: PCP Server DHCPv4 Option

The description of the fields is as follows:

Code: OPTION_PCP_SERVER (TBA, see Section 9.2);
Length: Includes the length of included IP address(es) in octets; MUST be a multiple of 4.
PCP server IPv4 Address(s): Contains one or more IPv4 addresses of the PCP server to be used by the PCP client.

4.2. Client Behavior

The DHCPv4 client expresses the intent to get OPTION_PCP_SERVER by specifying it in Parameter Request List Option [RFC2132].

The client MUST be prepared to receive multiple instances of the DHCPv4 PCP server option; each instance is treated as a separate PCP server.

The client MUST be prepared to receive one or multiple IPv4 addresses in the same PCP server option.

When multiple instances of the PCP server DHCPv4 option or multiple IPv4 addresses are received from the DHCPv4 server, the PCP client follows the behavior specified in [I-D.ietf-pcp-server-selection].

5. Configuration Guidelines (Server Side)

DHCP servers supporting the DHCP PCP server option can be configured with a list of IP addresses of the PCP server(s). If multiple IP addresses are configured, the DHCP server should be explicitly configured whether all or some of these addresses refer to:

the same PCP server: the DHCP server returns multiple addresses in the same instance of the DHCP PCP server option.
distinct PCP servers: the DHCP server returns multiple instances of the DHCP PCP server option to the requesting client; each instance is referring to a distinct PCP server. For example, multiple OPTION_PCP_SERVER instances may be configured to a PCP client in some deployment contexts such as multi-homing. It is out of scope of this document to enumerate all deployment scenarios that require multiple OPTION_PCP_SERVER instances to be returned.

The DHCP server may be configured with one or multiple FQDNs of the PCP server(s). In such case, the DHCP server must resolve these FQDNs into one or a list of IP addresses from pre-configured DNS server(s). If multiple FQDNs are configured to the DHCP server, the DHCP server must include multiple OPTION_PCP_SERVER instances; each of them carries one or a list of IP addresses that resulted from the FQDN resolution. DHCPv4 servers supporting PCP server option must resolve any configured FQDN into an IPv4 address while DHCPv6 servers may resolve any configured FQDN into an IPv6 and/or IPv4 address. If an IPv4 address is retrieved by the DHCPv6 server, the corresponding IPv4-mapped IPv6 address is included in the OPTION_PCP_SERVER DHPCv6 option. If both IPv4 and IPv6 addresses are retrieved by the DHCPv6 server, these addresses are included in the same OPTION_PCP_SERVER DHPCv6 option (IPv4 addresses are represented as IPv4-mapped IPv6 addresses).

Discussion: The motivation for this design is to accommodate deployment cases where an IPv4 connectivity service is provided while only DHPCv6 is in use (e.g., an IPv4-only PCP server in a DS-Lite context [RFC6333]).

For guidelines on providing context-specific configuration information (e.g., returning a regional-based configuration), and information on how a server might be configured with FQDNs that get resolved on demand, see [I-D.lemon-dhc-topo-conf].

6. Dual-Stack Hosts

A Dual-Stack host may receive an OPTION_PCP_SERVER via both DHCPv4 and DHCPv6. The content of these OPTION_PCP_SERVER options may refer to the same or distinct PCP Servers. This is deployment-specific and as such it is out of scope of this document.

7. Hosts with Multiple Interfaces

A host may have multiple network interfaces (e.g, 3G, IEEE 802.11, etc.); each configured differently. Each PCP server learned MUST be associated with the interface via which it was learned. Refer to [I-D.ietf-pcp-server-selection] and Section 8.4 of [RFC6887] for more discussion on multi-interface considerations.

8. Security Considerations

The security considerations in [RFC2131] and [RFC3315] are to be considered. PCP-related security considerations are discussed in [RFC6887].

9. IANA Considerations

9.1. DHCPv6 Option

IANA is requested to assign the following new DHCPv6 Option Code in the registry maintained in http://www.iana.org/assignments/dhcpv6-parameters:

Option Name	Value
OPTION_PCP_SERVER	TBA

9.2. DHCPv4 Option

IANA is requested to assign the following new DHCPv4 Option Code in the registry maintained in http://www.iana.org/assignments/bootp-dhcp-parameters/:

Option Name	Value
OPTION_PCP_SERVER	TBA

10. Acknowledgements

Many thanks to B. Volz, C. Jacquenet, R. Maglione, D. Thaler, T. Mrugalski, T. Reddy, S. Cheshire and M. Wasserman for their review and comments.

Special thanks to T. Lemon for the review and his continuous effort to enhance this specification.

11. References

11.1. Normative References

[RFC2119]	Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3315]	Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC2131]	Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997.
[RFC4291]	Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006.
[RFC2132]	Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor Extensions", RFC 2132, March 1997.
[I-D.ietf-pcp-server-selection]	Boucadair, M., Penno, R., Wing, D., Patil, P. and T. Reddy, "PCP Server Selection", Internet-Draft draft-ietf-pcp-server-selection-00, November 2012.
[RFC6887]	Wing, D., Cheshire, S., Boucadair, M., Penno, R. and P. Selkirk, "Port Control Protocol (PCP)", RFC 6887, April 2013.

11.2. Informative References

[I-D.lemon-dhc-topo-conf]	Lemon, T., "Customizing DHCP Configuration on the Basis of Network Topology", Internet-Draft draft-lemon-dhc-topo-conf-01, April 2013.
[RFC6333]	Durand, A., Droms, R., Woodyatt, J. and Y. Lee, "Dual-Stack Lite Broadband Deployments Following IPv4 Exhaustion", RFC 6333, August 2011.
[RFC6052]	Bao, C., Huitema, C., Bagnulo, M., Boucadair, M. and X. Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052, October 2010.

Authors' Addresses

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

Reinaldo Penno Cisco USA EMail: repenno@cisco.com

Dan Wing Cisco Systems, Inc. 170 West Tasman Drive San Jose, California 95134 USA EMail: dwing@cisco.com

Abstract

Requirements Language

Status of This Memo

Copyright Notice

Table of Contents