Network Working Group                                            B. Volz
Request for Comments: 4580                           Cisco Systems, Inc.
Category: Standards Track                                      June 2006


         Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
                    Relay Agent Subscriber-ID Option

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This memo defines a new Relay Agent Subscriber-ID option for the
   Dynamic Host Configuration Protocol for IPv6 (DHCPv6).  The option
   allows a DHCPv6 relay agent to associate a stable "Subscriber-ID"
   with DHCPv6 client messages in a way that is independent of the
   client and of the underlying physical network infrastructure.

Table of Contents

   1. Introduction ....................................................2
   2. The Relay Agent Subscriber-ID Option ............................2
   3. DHCPv6 Relay Agent Behavior .....................................3
   4. DHCPv6 Server Behavior ..........................................3
   5. Security Considerations .........................................4
   6. IANA Considerations .............................................4
   7. Acknowledgements ................................................4
   8. References ......................................................4
      8.1. Normative References .......................................4
      8.2. Informative References .....................................4

1.  Introduction

   DHCPv6 [1] provides IP addresses and configuration information for
   IPv6 clients.  It includes a relay agent capability, in which
   processes within the network infrastructure receive multicast
   messages from clients and relay them to DHCPv6 servers.  In some
   network environments, it will be useful for the relay agent to add
   information to the DHCPv6 message before relaying it.

   The information that relay agents supply can also be used in the
   server's decision-making about the addresses, delegated prefixes [2],
   and configuration parameters that the client is to receive.

   In many service-provider environments, it is believed to be desirable
   to associate some provider-specific information with clients' DHCPv6
   messages that is independent of the physical network configuration
   and that the relay agent has learned through some means that is
   outside the scope of this memo.

2.  The Relay Agent Subscriber-ID Option

   In complex service provider environments, there is a need to connect
   a customer's DHCPv6 configuration with the customer's administrative
   information.  The Relay Agent Subscriber-ID option carries a value
   that can be independent of the physical network configuration through
   which the subscriber is connected.  This value complements, and might
   well be used in addition to, the network-based information.  The
   "subscriber-id" assigned by the provider is intended to be stable as
   customers connect through different paths, and as network changes
   occur.

   The subscriber-id information allows the service provider to assign/
   activate subscriber-specific actions; e.g., assignment of specific IP
   addresses, prefixes, DNS configuration, trigger accounting, etc.
   This option is de-coupled from the access network's physical
   structure, so a subscriber that moves from one access-point to
   another, for example, would not require reconfiguration at the
   service provider's DHCPv6 servers.

   The subscriber-id information is only intended for use within a
   single administrative domain and is only exchanged between the relay
   agents and DHCPv6 servers within that domain.  Therefore, the format
   and encoding of the data in the option is not standardized, and this
   specification does not establish any semantic requirements on the
   data.  This specification only defines the option for conveying this
   information from relay agents to DHCPv6 servers.

   However, as the DHCPv4 Subscriber-ID suboption [3] specifies Network
   Virtual Terminal (NVT) American Standard Code for Information
   Interchange (ASCII) [4] encoded data, in environments where both
   DHCPv4 [5] and DHCPv6 are being used, it may be beneficial to use
   that encoding.

   The format of the DHCPv6 Relay Agent Subscriber-ID option is shown
   below:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     OPTION_SUBSCRIBER_ID      |         option-len            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .                                                               .
   .                         subscriber-id                         .
   .                                                               .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      option-code      OPTION_SUBSCRIBER_ID (38)

      option-len       length, in octets, of the subscriber-id field.
                       The minimum length is 1 octet.

      subscriber-id    The subscriber's identity.

3.  DHCPv6 Relay Agent Behavior

   DHCPv6 relay agents may be configured to include a Subscriber-ID
   option in relayed (RELAY-FORW) DHCPv6 messages.  How the subscriber-
   id is assigned and the mechanisms used to configure it are outside
   the scope of this memo.

4.  DHCPv6 Server Behavior

   This option provides additional information to the DHCPv6 server.
   The DHCPv6 server may use this information, if available, in addition
   to other relay agent option data, other options included in the
   DHCPv6 client messages, and physical network topology information in
   order to assign IP addresses, delegate prefixes, and/or other
   configuration parameters to the client.  There is no special
   additional processing for this option.

   There is no requirement that a server return this option and its data
   in a RELAY-REPLY message.

5.  Security Considerations

   As the subscriber-id option is only exchanged between relay agents
   and DHCPv6 servers, [1], Section 21.1, provides details on securing
   DHCPv6 messages sent between servers and relay agents.  [1], Section
   23, provides general DHCPv6 security considerations.

6.  IANA Considerations

   IANA has assigned a DHCPv6 option code (38) for the Relay Agent
   Subscriber-ID Option.

7.  Acknowledgements

   Thanks to Richard Johnson, Theyn Palaniappan, and Mark Stapp as this
   document is essentially an edited version of their memo [3].

8.  References

8.1.  Normative References

   [1]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M.
        Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
        RFC 3315, July 2003.

8.2.  Informative References

   [2]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host
        Configuration Protocol (DHCP) version 6", RFC 3633, December
        2003.

   [3]  Johnson, R., Palaniappan, T., and M. Stapp, "Subscriber-ID
        Suboption for the Dynamic Host Configuration Protocol (DHCP)
        Relay Agent Option", RFC 3993, March 2005.

   [4]  Postel, J. and J. Reynolds, "Telnet Protocol Specification", STD
        8, RFC 854, May 1983.

   [5]  Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
        March 1997.

Author's Address

   Bernard Volz
   Cisco Systems, Inc.
   1414 Massachusetts Ave.
   Boxborough, MA  01719
   USA

   Phone: +1 978 936 0382
   EMail: volz@cisco.com

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