RFC 3256 (rfc3256) - Page 1 of 5

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

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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
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