Vendor-Specific Information Suboption for the Dynamic Host Configuration Protocol (DHCP) Relay Agent Option
RFC 4243

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Network Working Group                                           M. Stapp
Request for Comments: 4243                                    R. Johnson
Category: Standards Track                                 T. Palaniappan
                                                     Cisco Systems, Inc.
                                                           December 2005

             Vendor-Specific Information Suboption for the
     Dynamic Host Configuration Protocol (DHCP) Relay Agent 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 (2005).

Abstract

   This memo defines a new Vendor-Specific Information suboption for the
   Dynamic Host Configuration Protocol's (DHCP) relay agent information
   option.  The suboption allows a DHCP relay agent to include vendor-
   specific information in the DHCP messages it forwards, as configured
   by its administrator.

Table of Contents

   1. Introduction ....................................................2
   2. Requirements Terminology ........................................2
   3. The Vendor-Specific Suboption ...................................2
   4. Relay Agent Behavior ............................................4
   5. DHCP Server Behavior ............................................4
   6. Security Considerations .........................................4
   7. IANA Considerations .............................................5
   8. Acknowledgements ................................................5
   Normative References ...............................................5
   Informative References .............................................5

Stapp, et al.               Standards Track                     [Page 1]
RFC 4243            Vendor-Specific Relay Suboption        December 2005

1.  Introduction

   DHCP (RFC 2131 [2]) provides IP addresses and configuration
   information for IPv4 clients.  It includes a relay agent capability,
   in which processes within the network infrastructure receive
   broadcast messages from clients and forward them to DHCP servers as
   unicast messages.  In network environments like DOCSIS data-over-
   cable and xDSL, for example, it has proven useful for the relay agent
   to add information to the DHCP message before forwarding it, using
   the relay agent information option (RFC 3046 [3]).

   Servers that recognize the relay agent option echo it back in their
   replies, and some of the information that relays add may be used to
   help an edge device efficiently return replies to clients.  The
   information that relays supply can also be used in the server's
   decision making about the addresses and configuration parameters that
   the client should receive.

   In many environments, it's desirable to associate some vendor- or
   provider-specific information with the clients' DHCP messages.  This
   is often done using the relay agent information option.  RFC 3046
   defines Remote-ID and Circuit-ID sub-options that are used to carry
   such information.  The values of those suboptions, however, are
   usually based on some network resource, such as an IP address of a
   network access device, an ATM Virtual Circuit identifier, or a DOCSIS
   cable-modem identifier.  As a result, the values carried in these
   suboptions are dependent on the physical network configuration.  The
   Vendor-Specific suboption allows administrators to associate other
   useful data with relayed DHCP messages.

2.   Requirements 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 RFC 2119 [1].

3.  The Vendor-Specific Suboption

   This memo defines a new DHCP relay agent option suboption that
   carries vendor-defined data.  The suboption takes a form similar to
   the Vendor-Identifying, Vendor-Specific Option [7].

Stapp, et al.               Standards Track                     [Page 2]
RFC 4243            Vendor-Specific Relay Suboption        December 2005

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