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The DOCSIS (Data-Over-Cable Service Interface Specifications) Device Class DHCP (Dynamic Host Configuration Protocol) Relay Agent Information Sub-option (RFC3256)

IP.com Disclosure Number: IPCOM000007736D
Original Publication Date: 2002-Apr-01
Included in the Prior Art Database: 2002-Apr-18
Document File: 6 page(s) / 9K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

D. Jones: AUTHOR [+2]

Abstract

This document proposes a new sub-option to the DHCP (Dynamic Host Configuration Protocol) Relay Agent Information Option. This new sub-option is for use with DOCSIS (Data-Over-Cable Service Interface Specifications) cable modems and describes a "device class" to which the cable modem belongs. The cable modem signals its device class information to the Relay Agent using DOCSIS signaling, and the Relay Agent forwards the device class information to the DHCP Server which can then make a policy decision based on it.

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This is the abbreviated version, containing approximately 41% of the total text.

Network Working Group                                           D. Jones

Request for Comments: 3256                               YAS Corporation

Category: Standards Track                                      R. Woundy

                                                          AT&T Broadband

                                                              April 2002

  The DOCSIS (Data-Over-Cable Service Interface Specifications) Device

      Class DHCP (Dynamic Host Configuration Protocol) Relay Agent

                         Information Sub-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.

Abstract

   This document proposes a new sub-option to the DHCP (Dynamic Host

   Configuration Protocol) Relay Agent Information Option.  This new

   sub-option is for use with DOCSIS (Data-Over-Cable Service Interface

   Specifications) cable modems and describes a "device class" to which

   the cable modem belongs.  The cable modem signals its device class

   information to the Relay Agent using DOCSIS signaling, and the Relay

   Agent forwards the device class information to the DHCP Server which

   can then make a policy decision based on it.

1.  Introduction

   The "Relay Agent Information" Option is described in [1] and includes

   several Relay Agent Information sub-options.  This RFC proposes an

   additional sub-option for use with DOCSIS cable modems.  This sub-

   option is added by DHCP relay agents which terminate cable modems.

   The sub-option encodes an identifier of the device class to which the

   cable modem belongs.  It is intended for use by DHCP servers to make

   policy decisions based on the device class of the host.

   The motivation for using a Relay Agent Information sub-option, rather

   than a new or existing DHCP option, is the introduction of CPE

   Controlled Cable Modems (CCCMs) [2].  In an implementation of a CCCM,

   the modem firmware controls DOCSIS signaling, but the attached

   computer (CPE) manages other protocol activities -- particularly DHCP

   client message handling.  The assumption of this document is that it

Jones & Woundy              Standards Track                     [Page 1]

RFC 3256              The DOCSIS Device Class DHCP            April 2002

   is better to trust the operation of the CCCM firmware, than to trust

   the operation of CCCM software running on the attached computer

   (e.g., a standard PC).

   The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"

   in this document are to be interpreted as described in RFC 2119 [4].

2.  DOCSIS Device Class Sub-option

   The DOCSIS RFI specification [3] specifies the Device Class encoding

   within the payload of the Device Class Identification Request (DCI-

   REQ) message.  The relay agent MUST pass the Device Class value

   unchanged to the DHCP server.  Possible uses of this field include:

      o  host endpoint information

      o  host hardware capabilities

      o  host software capabilities

      o  host options information

   DOCSIS defines the Device Class to be a 32-bit field where individual

   bits represent individual attributes of the CM.  Bit #0 is the least

   signific...