The User Class Option for DHCP
RFC 3004

Document Type RFC - Proposed Standard (November 2000; No errata)
Authors Burcak Beser  , Ye Gu  , Jerome Privat  , Ramesh Vyaghrapuri  , Ralph Droms  , Ann Demirtjis  , Glenn Stump 
Last updated 2013-03-02
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Network Working Group                                           G. Stump
Request for Comments: 3004                                           IBM
Category: Standards Track                                       R. Droms
                                                           Cisco Systems
                                                                   Y. Gu
                                                          R. Vyaghrapuri
                                                            A. Demirtjis
                                                                B. Beser
                                        Pacific Broadband Communications
                                                               J. Privat
                                                          Northstream AB
                                                           November 2000

                     The User Class Option for DHCP

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 (2000).  All Rights Reserved.


   This option is used by a Dynamic Host Configuration Protocol (DHCP)
   client to optionally identify the type or category of user or
   applications it represents.  The information contained in this option
   is an opaque field that represents the user class of which the client
   is a member.  Based on this class, a DHCP server selects the
   appropriate address pool to assign an address to the client and the
   appropriate configuration parameters.  This option should be
   configurable by a user.

1. Introduction

   DHCP administrators may define specific user class identifiers to
   convey information about a client's software configuration or about
   its user's preferences.  For example, the User Class option can be
   used to configure all clients of people in the accounting department
   with a different printer than clients of people in the marketing

Stump, et al.               Standards Track                     [Page 1]
RFC 3004             The User Class Option for DHCP        November 2000

2. Requirements Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [3].

3. DHCP Terminology

   o "DHCP client"
     A DHCP client or "client" is an Internet host using DHCP to obtain
     configuration parameters such as a network address.

   o "DHCP server"
     A DHCP server or "server" is an Internet host that returns
     configuration parameters to DHCP clients.

   o "binding"
     A binding is a collection of configuration parameters, including at
     least an IP address, associated with or "bound to" a DHCP client.
     Bindings are managed by DHCP servers.

4. User Class option

   This option is used by a DHCP client to optionally identify the type
   or category of user or applications it represents.  A DHCP server
   uses the User Class option to choose the address pool it allocates an
   address from and/or to select any other configuration option.

   This option is a DHCP option [1, 2].

   This option MAY carry multiple User Classes.  Servers may interpret
   the meanings of multiple class specifications in an implementation
   dependent or configuration dependent manner, and so the use of
   multiple classes by a DHCP client should be based on the specific
   server implementation and configuration which will be used to process
   that User class option.

   The format of this option is as follows:

         Code   Len   Value
        +-----+-----+---------------------  . . .  --+
        | 77  |  N  | User Class Data ('Len' octets) |
        +-----+-----+---------------------  . . .  --+

   where Value consists of one or more instances of User Class Data.
   Each instance of User Class Data is formatted as follows:

Stump, et al.               Standards Track                     [Page 2]
RFC 3004             The User Class Option for DHCP        November 2000

         UC_Len_i     User_Class_Data_i
        +--------+------------------------  . . .  --+
        |  L_i   | Opaque-Data ('UC_Len_i' octets)   |
        +--------+------------------------  . . .  --+

   Each User Class value (User_Class_Data_i) is indicated as an opaque
   field.  The value in UC_Len_i does not include the length field
   itself and MUST be non-zero.  Let m be the number of User Classes
   carried in the option.  The length of the option as specified in Len
   must be the sum of the lengths of each of the class names plus m:
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