draft-ietf-dhc-agentoptions-device-class-02.txt   draft-ietf-dhc-agentoptions-device-class-03.txt 
INTERNET-DRAFT D. Jones INTERNET-DRAFT D. Jones
Dynamic Host Control Working Group YAS Corporation Dynamic Host Control Working Group YAS Corporation
Expires March 2002 R. Woundy Expires April 2002 R. Woundy
Cisco Cisco
September 2001 October 2001
Addition of Device Class to Agent Options Addition of Device Class to Agent Options
<draft-ietf-dhc-agentoptions-device-class-02.txt> <draft-ietf-dhc-agentoptions-device-class-03.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
skipping to change at page 2, line 9 skipping to change at page 2, line 9
modems and describes a "device class" to which the cable modem modems and describes a "device class" to which the cable modem
belongs. The cable modem signals its device class information to the belongs. The cable modem signals its device class information to the
Relay Agent using DOCSIS signalling, and the Relay Agent forwards the Relay Agent using DOCSIS signalling, and the Relay Agent forwards the
device class information to the DHCP Server which can then make a device class information to the DHCP Server which can then make a
policy decision based on it. policy decision based on it.
1. Introduction 1. Introduction
DHCP Agent Options is described in [1] and includes several Relay DHCP Agent Options is described in [1] and includes several Relay
Agent Information sub-options. This I-D proposes an additional sub- Agent Information sub-options. This I-D proposes an additional sub-
option for use with DOCSIS cable modems. This sub-option MAY be option for use with DOCSIS cable modems. This sub-option is added by
added by DHCP relay agents which terminate cable modems. The sub- DHCP relay agents which terminate cable modems. The sub-option
option encodes an identifier of the device class to which the cable encodes an identifier of the device class to which the cable modem
modem belongs. It is intended for use by DHCP servers to make policy belongs. It is intended for use by DHCP servers to make policy deci-
decisions based on the device class of the host. sions 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 Con-
trolled Cable Modems (CCCMs) [2]. In an implementation of a CCCM, the trolled Cable Modems (CCCMs) [2]. In an implementation of a CCCM, the
modem firmware controls DOCSIS signalling, but the attached computer modem firmware controls DOCSIS signalling, but the attached computer
(CPE) manages other protocol activities -- particularly DHCP client (CPE) manages other protocol activities -- particularly DHCP client
message handling. The assumption of this document is that it is message handling. The assumption of this document is that it is
better to trust the operation of the CCCM firmware, than to trust the 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 operation of CCCM software running on the attached computer (e.g. a
standard PC). 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. Device Class Sub-option 2. 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 passes 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
The Device Class sub-option is coded as follows: 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
significant bit of the field. Bits are set to 1 to select the attri-
butes defined below.
bit #0 - CPE Controlled Cable Modem (CCCM)
bits #1-31 - Reserved and set to zero
The device class sub-option is coded as follows:
SubOpt Len Device Class SubOpt Len Device Class
+------+------+------+------+------+------+------+------+-- +------+------+------+------+------+------+
| TBD | n | d1 | d2 | d3 | d4 | d5 | d6 | ... | TBD | 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. DHCP
servers MAY use the Device Class for IP and other parameter assignment servers MAY use the device class for IP and other parameter assignment
policies for cable modems. 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.
Operation of the Device Class sub-option also relies on an implied Operation of the device class sub-option also 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 signalling. According to
DOCSIS specifications, the cable modem firmware always controls DOCSIS specifications, the cable modem firmware always controls
DOCSIS signalling, but may not control DHCP client message handling DOCSIS signalling, 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 is
trustworthy for DOCSIS signalling information. trustworthy for DOCSIS signalling information.
This document introduces a new identifier, the Device Class sub- This document introduces a new identifier, the device class sub-
option, that is provided by the relay agent device and is assumed to option, that is provided by the relay agent device and is assumed to
be trusted. Cryptographic or other techniques to authenticate the 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. References 4. IANA Considerations
IANA has assigned a value of TBD from the DHCP Relay Agent Sub-
options space [RFC 3046] for the device class sub-option defined in
section 2.
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 to
Customer Premise Equipment Interface Specification SP-CMCI-I06- Customer Premise Equipment Interface Specification SP-CMCI-I06-
010829", DOCSIS, August 2001, http://www.cablemodem.com. 010829", DOCSIS, August 2001, 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-I07-010829",
DOCSIS, August 2001, http://www.cablemodem.com. DOCSIS, August 2001, http://www.cablemodem.com.
5. Authors' Addresses [4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
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 Cisco Systems
250 Apollo Drive 250 Apollo Drive
Chelmsford, MA 01824 Chelmsford, MA 01824
Phone: (978) 244-8000 Phone: (978) 244-8000
EMail: rwoundy@cisco.com EMail: rwoundy@cisco.com
6. Full Copyright Statement 7. Full Copyright Statement
Copyright (C) The Internet Society (2001). All Rights Reserved. Copyright (C) The Internet Society (2001). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
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