As per Relevance of the word document, we have this rfc below:
Network Working Group D.
Request for Comments: 3256 YAS
Category: Standards Track R.
AT&T
April 2002
The DOCSIS (Data-Over-Cable Service Interface Specifications)
Class DHCP (Dynamic Host Configuration Protocol) Relay
Information Sub-
Status of this
This document specifies an Internet standards track protocol for
Internet community, and requests discussion and suggestions
improvements. Please refer to the current edition of the "
Official Protocol Standards" (STD 1) for the standardization
and status of this protocol. Distribution of this memo is unlimited
This document proposes a new sub-option to the DHCP (Dynamic
Configuration Protocol) Relay Agent Information Option. This
sub-option is for use with DOCSIS (Data-Over-Cable Service
Specifications) cable modems and describes a "device class" to
the cable modem belongs. The cable modem signals its device
information to the Relay Agent using DOCSIS signaling, and the
Agent forwards the device class information to the DHCP Server
can then make a policy decision based on it
1.
The "Relay Agent Information" Option is described in [1] and
several Relay Agent Information sub-options. This RFC proposes
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
cable modem belongs. It is intended for use by DHCP servers to
policy decisions based on the device class of the host
The motivation for using a Relay Agent Information sub-option,
than a new or existing DHCP option, is the introduction of
Controlled Cable Modems (CCCMs) [2]. In an implementation of a CCCM
the modem firmware controls DOCSIS signaling, but the
computer (CPE) manages other protocol activities -- particularly
client message handling. The assumption of this document is that
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
the operation of CCCM software running on the attached
(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-
The DOCSIS RFI specification [3] specifies the Device Class
within the payload of the Device Class Identification Request (DCI
REQ) message. The relay agent MUST pass the Device Class
unchanged to the DHCP server. Possible uses of this field include
o host endpoint
o host hardware
o host software
o host options
DOCSIS defines the Device Class to be a 32-bit field where
bits represent individual attributes of the CM. Bit #0 is the
significant bit of the field. Bits are set to 1 to select
attributes defined below
bit #0 - CPE Controlled Cable Modem (CCCM
bits #1-31 - Reserved and set to
The DOCSIS Device Class sub-option is coded as follows
SubOpt Len Device
+------+------+------+------+------+------+
| 4 | 4 | d1 | d2 | d3 | d4 |
+------+------+------+------+------+------+
The DHCP server needs to understand the meaning of this sub-option
order to offer different policy options in its reply to the host
DHCP servers MAY use the device class for IP and other
assignment policies for cable modems
Jones & Woundy Standards Track [Page 2]
RFC 3256 The DOCSIS Device Class DHCP April 2002
3. Security
Operation of the DHCP Relay Agent Information Option relies on
implied trusted relationship between the DHCP relay agent and
DHCP server. The discussion of security considerations for the
relay agent information option [1] apply to this sub-option as well
Operation of the DOCSIS Device Class sub-option relies on an
trusted relationship between the DHCP client (i.e., the cable modem
and the DHCP relay agent, through DOCSIS signaling. According
DOCSIS specifications [2], the cable modem firmware always
DOCSIS signaling, but cannot control DHCP client message
(e.g., CCCMs). This document assumes that the cable modem
is trustworthy for DOCSIS signaling information
This document introduces a new identifier, the DOCSIS Device
sub-option, that is provided by the relay agent device and is
to be trusted. Cryptographic or other techniques to authenticate
device class are beyond the scope of this document
4. IANA
IANA has assigned a value of 4 from the DHCP Relay Agent Sub-
space [RFC 3046] for the DOCSIS Device Class sub-option defined
section 2.
5.
[1] Patrick, M., "DHCP Relay Agent Information Option", RFC 3046,
January 2001.
[2] "Data-Over-Cable Service Interface Specifications: Cable
to Customer Premise Equipment Interface Specification SP-CMCI
I07-020301", DOCSIS, March 2002, http://www.cablemodem.com
[3] "Data-Over-Cable Service Interface Specifications: Cable
Radio Frequency Interface Specification SP-RFIv1.1-I08-020301",
DOCSIS, March 2002, http://www.cablemodem.com
[4] Bradner, S., "Key words for use in RFCs to Indicate
Levels", BCP 14, RFC 2119, March 1997.
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RFC 3256 The DOCSIS Device Class DHCP April 2002
6. Authors'
Doug
YAS
300 Brickstone
Andover, MA 01810
Phone: (303) 661-3823
EMail: doug@yas.
Rich
AT&T
27 Industrial
Chelmsford, MA 01824
Phone: (978) 244-4010
EMail: rwoundy@broadband.att.
Jones & Woundy Standards Track [Page 4]
RFC 3256 The DOCSIS Device Class DHCP April 2002
7. Full Copyright
Copyright (C) The Internet Society (2002). All Rights Reserved
This document and translations of it may be copied and furnished
others, and derivative works that comment on or otherwise explain
or assist in its implementation may be prepared, copied,
and distributed, in whole or in part, without restriction of
kind, provided that the above copyright notice and this paragraph
included on all such copies and derivative works. However,
document itself may not be modified in any way, such as by
the copyright notice or references to the Internet Society or
Internet organizations, except as needed for the purpose
developing Internet standards in which case the procedures
copyrights defined in the Internet Standards process must
followed, or as required to translate it into languages other
English
The limited permissions granted above are perpetual and will not
revoked by the Internet Society or its successors or assigns
This document and the information contained herein is provided on
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE
Funding for the RFC Editor function is currently provided by
Internet Society
Jones & Woundy Standards Track [Page 5]
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