draft-ietf-dhc-agentoptions-device-class-03.txt   rfc3256.txt 
INTERNET-DRAFT D. Jones Network Working Group D. Jones
Dynamic Host Control Working Group YAS Corporation Request for Comments: 3256 YAS Corporation
Expires April 2002 R. Woundy Category: Standards Track R. Woundy
Cisco AT&T Broadband
October 2001 April 2002
Addition of Device Class to Agent Options The DOCSIS (Data-Over-Cable Service Interface Specifications) Device
<draft-ietf-dhc-agentoptions-device-class-03.txt> Class DHCP (Dynamic Host Configuration Protocol) Relay Agent
Information Sub-option
Status of this Memo Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract Abstract
This document proposes a new sub-option to the DHCP Relay Information This document proposes a new sub-option to the DHCP (Dynamic Host
Agent Option. This new sub-option is for use with DOCSIS cable Configuration Protocol) Relay Agent Information Option. This new
modems and describes a "device class" to which the cable modem sub-option is for use with DOCSIS (Data-Over-Cable Service Interface
belongs. The cable modem signals its device class information to the Specifications) cable modems and describes a "device class" to which
Relay Agent using DOCSIS signalling, and the Relay Agent forwards the the cable modem belongs. The cable modem signals its device class
device class information to the DHCP Server which can then make a information to the Relay Agent using DOCSIS signaling, and the Relay
policy decision based on it. Agent forwards the device class information to the DHCP Server which
can then make a policy decision based on it.
1. Introduction 1. Introduction
DHCP Agent Options is described in [1] and includes several Relay The "Relay Agent Information" Option is described in [1] and includes
Agent Information sub-options. This I-D proposes an additional sub- several Relay Agent Information sub-options. This RFC proposes an
option for use with DOCSIS cable modems. This sub-option is added by additional sub-option for use with DOCSIS cable modems. This sub-
DHCP relay agents which terminate cable modems. The sub-option option is added by DHCP relay agents which terminate cable modems.
encodes an identifier of the device class to which the cable modem The sub-option encodes an identifier of the device class to which the
belongs. It is intended for use by DHCP servers to make policy deci- cable modem belongs. It is intended for use by DHCP servers to make
sions based on the device class of the host. policy decisions based on the device class of the host.
The motivation for using a Relay Agent Information sub-option, rather The motivation for using a Relay Agent Information sub-option, rather
than a new or existing DHCP option, is the introduction of CPE Con- than a new or existing DHCP option, is the introduction of CPE
trolled Cable Modems (CCCMs) [2]. In an implementation of a CCCM, the Controlled Cable Modems (CCCMs) [2]. In an implementation of a CCCM,
modem firmware controls DOCSIS signalling, but the attached computer the modem firmware controls DOCSIS signaling, but the attached
(CPE) manages other protocol activities -- particularly DHCP client computer (CPE) manages other protocol activities -- particularly DHCP
message handling. The assumption of this document is that it is client message handling. The assumption of this document is that it
better to trust the operation of the CCCM firmware, than to trust the is better to trust the operation of the CCCM firmware, than to trust
operation of CCCM software running on the attached computer (e.g. a the operation of CCCM software running on the attached computer
standard PC). (e.g., a standard PC).
The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT" and "MAY" in The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
this document are to be interpreted as described in RFC 2119 [4]. in this document are to be interpreted as described in RFC 2119 [4].
2. Device Class Sub-option 2. DOCSIS Device Class Sub-option
The DOCSIS RFI specification [3] specifies the Device Class encoding The DOCSIS RFI specification [3] specifies the Device Class encoding
within the payload of the Device Class Identification Request (DCI- within the payload of the Device Class Identification Request (DCI-
REQ) message. The relay agent MUST pass the Device Class value REQ) message. The relay agent MUST pass the Device Class value
unchanged to the DHCP server. Possible uses of this field include: unchanged to the DHCP server. Possible uses of this field include:
o host endpoint information o host endpoint information
o host hardware capabilities o host hardware capabilities
o host software capabilities o host software capabilities
o host options information o host options information
DOCSIS defines the Device Class to be a 32-bit field where individual 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 bits represent individual attributes of the CM. Bit #0 is the least
significant bit of the field. Bits are set to 1 to select the attri- significant bit of the field. Bits are set to 1 to select the
butes defined below. attributes defined below.
bit #0 - CPE Controlled Cable Modem (CCCM) bit #0 - CPE Controlled Cable Modem (CCCM)
bits #1-31 - Reserved and set to zero bits #1-31 - Reserved and set to zero
The device class sub-option is coded as follows:
The DOCSIS Device Class sub-option is coded as follows:
SubOpt Len Device Class SubOpt Len Device Class
+------+------+------+------+------+------+ +------+------+------+------+------+------+
| TBD | 4 | d1 | d2 | d3 | d4 | | 4 | 4 | d1 | d2 | d3 | d4 |
+------+------+------+------+------+------+ +------+------+------+------+------+------+
The DHCP server needs to understand the meaning of this sub-option in The DHCP server needs to understand the meaning of this sub-option in
order to offer different policy options in its reply to the host. DHCP order to offer different policy options in its reply to the host.
servers MAY use the device class for IP and other parameter assignment DHCP servers MAY use the device class for IP and other parameter
policies for cable modems. assignment policies for cable modems.
3. Security Considerations 3. Security Considerations
Operation of the DHCP Relay Agent Information Option relies on an Operation of the DHCP Relay Agent Information Option relies on an
implied trusted relationship between the DHCP relay agent and the implied trusted relationship between the DHCP relay agent and the
DHCP server. DHCP server. The discussion of security considerations for the DHCP
relay agent information option [1] apply to this sub-option as well.
Operation of the device class sub-option also relies on an implied Operation of the DOCSIS Device Class sub-option relies on an implied
trusted relationship between the DHCP client (i.e. the cable modem) trusted relationship between the DHCP client (i.e., the cable modem)
and the DHCP relay agent, through DOCSIS signalling. According to and the DHCP relay agent, through DOCSIS signaling. According to
DOCSIS specifications, the cable modem firmware always controls DOCSIS specifications [2], the cable modem firmware always controls
DOCSIS signalling, but cannot control DHCP client message handling DOCSIS signaling, but cannot control DHCP client message handling
(e.g. CCCMs). This document assumes that the cable modem firmware is (e.g., CCCMs). This document assumes that the cable modem firmware
trustworthy for DOCSIS signalling information. is trustworthy for DOCSIS signaling information.
This document introduces a new identifier, the device class sub- This document introduces a new identifier, the DOCSIS Device Class
option, that is provided by the relay agent device and is assumed to sub-option, that is provided by the relay agent device and is assumed
be trusted. Cryptographic or other techniques to authenticate the to be trusted. Cryptographic or other techniques to authenticate the
device class are beyond the scope of this document. device class are beyond the scope of this document.
4. IANA Considerations 4. IANA Considerations
IANA has assigned a value of TBD from the DHCP Relay Agent Sub- IANA has assigned a value of 4 from the DHCP Relay Agent Sub-options
options space [RFC 3046] for the device class sub-option defined in space [RFC 3046] for the DOCSIS Device Class sub-option defined in
section 2. section 2.
5. References 5. References
[1] Patrick, M., "DHCP Relay Agent Information Option", RFC 3046, [1] Patrick, M., "DHCP Relay Agent Information Option", RFC 3046,
January 2001. January 2001.
[2] "Data-Over-Cable Service Interface Specifications: Cable Modem to [2] "Data-Over-Cable Service Interface Specifications: Cable Modem
Customer Premise Equipment Interface Specification SP-CMCI-I06- to Customer Premise Equipment Interface Specification SP-CMCI-
010829", DOCSIS, August 2001, http://www.cablemodem.com. I07-020301", DOCSIS, March 2002, http://www.cablemodem.com.
[3] "Data-Over-Cable Service Interface Specifications: Cable Modem [3] "Data-Over-Cable Service Interface Specifications: Cable Modem
Radio Frequency Interface Specification SP-RFIv1.1-I07-010829", Radio Frequency Interface Specification SP-RFIv1.1-I08-020301",
DOCSIS, August 2001, http://www.cablemodem.com. DOCSIS, March 2002, http://www.cablemodem.com.
[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement [4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
6. Authors' Addresses 6. Authors' Addresses
Doug Jones Doug Jones
YAS Corporation YAS Corporation
300 Brickstone Square 300 Brickstone Square
Andover, MA 01810 Andover, MA 01810
skipping to change at page 4, line 19 skipping to change at page 4, line 11
[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement [4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
6. Authors' Addresses 6. Authors' Addresses
Doug Jones Doug Jones
YAS Corporation YAS Corporation
300 Brickstone Square 300 Brickstone Square
Andover, MA 01810 Andover, MA 01810
Phone: (303) 661-3823 Phone: (303) 661-3823
EMail: doug@yas.com EMail: doug@yas.com
Rich Woundy Rich Woundy
Cisco Systems AT&T Broadband
250 Apollo Drive 27 Industrial Avenue
Chelmsford, MA 01824 Chelmsford, MA 01824
Phone: (978) 244-8000
EMail: rwoundy@cisco.com Phone: (978) 244-4010
EMail: rwoundy@broadband.att.com
7. Full Copyright Statement 7. Full Copyright Statement
Copyright (C) The Internet Society (2001). All Rights Reserved. Copyright (C) The Internet Society (2002). All Rights Reserved.
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Acknowledgement
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