DHC M. Stapp
Internet-Draft Cisco Systems, Inc.
Expires: December 15, 2008 June 13, 2008
The DHCPv4 Relay Agent Identifier Suboption
draft-ietf-dhc-relay-id-suboption-00.txt
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Copyright (C) The IETF Trust (2008).
Abstract
This memo defines a new Relay Agent Identifier suboption for the
Dynamic Host Configuration Protocol's (DHCP) Relay Agent Information
option. The suboption carries a unique identifier configured or
generated at the relay agent. The suboption allows a DHCP relay
agent to include the unique identifier in the DHCP messages it sends.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Suboption Format . . . . . . . . . . . . . . . . . . . . . . . 4
4. Generating a Relay Identifier . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7. Normative References . . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 5
Intellectual Property and Copyright Statements . . . . . . . . . . 6
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1. Introduction
The Dynamic Host Configuration Protocol for IPv4 (DHCPv4) [RFC2131]
provides IP addresses and configuration information for IPv4 clients.
It includes a relay agent capability, in which network elements
receive broadcast messages from clients and forward them to DHCP
servers as unicast messages. In many network environments, relay
agents add information to the DHCP messages before forwarding them,
using the Relay Agent Information option [RFC3046]. Servers that
recognize the relay information option echo it back in their replies.
DHCP typically identifies clients based on information in their DHCP
messages - such as the Client-Identifier option, or the value of the
chaddr field. In some networks, however, the location of a client,
its point of attachment to the network, is a more useful identifier.
In factory-floor networks (commonly called 'Industrial' networks),
for example, the role a device plays is often fixed and based on its
location. Using manual address configuration is possible (and is
common), but it would be beneficial if DHCP configuration could be
applied to these networks.
One way to provide connection-based identifiers for industrial
networks is to have the network elements acting as DHCP relay agents
supply information that the DHCP server can use as a client
identifier. A straightforward way to form identifier information is
to combine something that is unique within the scope of the network
element with something that uniquely identifies that network element.
There are several possibilities, but to improve interoperability we
describe a dedicated identifier that can be associated with the
network element and conveyed in a consistent way.
This specification introduces a Relay Agent Identifier suboption for
the Relay Information option. The Relay-Id suboption carries an
sequence of octets that is intended to identify the relay agent
uniquely within the administrative domain. The identifier may be
administratively configured: in some networks it may be adequate to
assign strings such as "switch1" and "switch2". Alternatively, the
identifier may be generated by the relay agent itself, and we specify
an algorithm from [RFC3315] for this purpose.
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].
DHCPv4 terminology is defined in [RFC2131], and the DHCPv4 Relay
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Agent Information Option in [RFC3046]. DUID terminology is in
[RFC3315].
3. Suboption Format
Format of the Relay Agent Identifier suboption:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|SUBOPT_RELAY_ID| length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ id (variable) |
. .
. .
. .
+---------------------------------------------------------------+
Where:
SUBOPT_RELAY_ID [TBD]
length the number of octets in the identifier; the
minimum length is one.
id 'length' octets of identifier
4. Generating a Relay Identifier
As described in Section 1, in some situations it may be useful for
network devices to generate identifiers themselves. Relay agents who
send the Relay Agent Identifier suboption using identifiers that are
not administratively-configured MUST be generated following the
procedures in the DUID section of [RFC3315]. Relay agents who use
generated identifiers should make the generated value available to
their administrators via their user-interface, through a log entry,
or through some other mechanism.
5. Security Considerations
Security issues with the Relay Agent Information option and its use
by servers in address assignment are discussed in [RFC3046] and
[RFC4030]. Relay agents who send the Relay Agent Identifier
suboption SHOULD use the Relay Agent Authentication suboption
[RFC4030] to provide integrity protection.
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6. IANA Considerations
We request that IANA assign a new suboption code from the registry of
DHCP Agent Sub-Option Codes maintained in
http://www.iana.org/assignments/bootp-dhcp-parameters.
Relay Agent Identifier Suboption [TBD]
7. Normative References
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, March 1997.
[RFC3046] Patrick, M., "DHCP Relay Agent Information Option",
RFC 3046, January 2001.
[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.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4030] Stapp, M. and T. Lemon, "The Authentication Suboption for
the Dynamic Host Configuration Protocol (DHCP) Relay Agent
Option", RFC 4030, March 2005.
Author's Address
Mark Stapp
Cisco Systems, Inc.
1414 Massachusetts Ave.
Boxborough, MA 01719
USA
Phone: +1 978 936 0000
Email: mjs@cisco.com
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