The User Class Option for DHCP
RFC 3004
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RFC - Proposed Standard
(November 2000; No errata)
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2013-03-02
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RFC 3004 (Proposed Standard)
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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
Microsoft
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.
Abstract
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
department.
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",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this
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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