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
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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.
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RFC 4580 Relay Agent Subscriber-ID June 2006
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.
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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.
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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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RFC 4580 Relay Agent Subscriber-ID June 2006
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