DHC Working Group Josh Littlefield
INTERNET-DRAFT Cisco Systems
Expires: March 2004 September 2003
Vendor-Identifying Vendor Options for DHCPv4
draft-ietf-dhc-vendor-00.txt
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Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
The DHCP options for Vendor Class and Vendor-Specific Information can
be ambiguous when a DHCP client represents multiple vendors. This
document defines two new options, modeled on the IPv6 options for
vendor class and vendor-specific information, which contain
Enterprise Numbers to remove ambiguity.
Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [1].
Table of Contents
1. Introduction...................................................2
2. Vendor-Identifying Vendor Class Option.........................2
3. Vendor-Identifying Vendor-Specific Information Option..........3
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4. IANA Considerations............................................5
5. Security Considerations........................................5
References........................................................5
Author's Address..................................................6
Acknowledgement...................................................7
1. Introduction
The DHCP protocol for IPv4 defines options to allow a client to
indicate its vendor type (option 60), and to allow the DHCP client
and server to exchange vendor-specific information (option 43) [2].
While there is no prohibition against passing multiple copies of
these options in a single packet, doing so would introduce ambiguity
of interpretation, particularly if conveying vendor-specific
information for multiple vendors. The vendor identified by option 60
defines the interpretation of option 43, which itself carries no
vendor identifier.
There are circumstances where an implementation may need to support
multiple, independently defined forms of vendor-specific information.
For example, implementations that must conform to an industry-
standard use of DHCPv4, to allow interoperability in a particular
technology space, may be required to support the vendor-specific
options of that industry group. But the same implementation may also
require support for vendor-specific options defined by the
manufacturer. In particular, this is an issue for vendors of devices
supporting CableLabs standards, such as DOCSIS, CableHome, and
PacketCable, since those standards define an industry-specific use
for options 60 and 43.
This document defines two new options, modeled on the IPv6 options
for vendor class and vendor-specific information [3], which contain
Enterprise Numbers to remove ambiguity. If desired, these new
options can be used in addition to the current vendor class and
vendor information options, whose definition is unaffected by this
document.
2. Vendor-Identifying Vendor Class Option
A DHCP client may use this option to unambiguously identify the
vendor that manufactured the hardware on which the client is running,
or an industry consortium to which the vendor belongs. The
information contained in the data area of this option is contained in
one or more opaque fields that identify details of the hardware
configuration.
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The format of the V-I Vendor Class option is:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_V-I VENDOR_CLASS | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| enterprise-number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. vendor-class-data .
. . . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code OPTION_V-I VENDOR_CLASS (to be assigned by
IANA)
option-len 4 + length of vendor class data field
enterprise-number The vendor's registered Enterprise Number as
registered with IANA [4].
vendor-class-data The hardware configuration of the host on
which the client is running.
Each instance of this option contains information corresponding to a
single Enterprise Number. Multiple instances of this option may be
present, and each is treated independently.
The vendor-class-data is composed of a series of separate items, each
of which describes some characteristic of the client's hardware
configuration or capabilities. Examples of vendor-class-data
instances might include the version of the operating system the
client is running or the amount of memory installed on the client.
Each instance of the vendor-class-data is formatted as follows:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
| vendor-class-len | opaque-data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
The vendor-class-len is two octets long and specifies the length of
the opaque vendor class data in network byte order.
3. Vendor-Identifying Vendor-Specific Information Option
DHCP Clients and servers may use this option to exchange vendor-
specific information.
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The format of the V-I Vendor-specific Information option is:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_V-I VENDOR_OPTS | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| enterprise-number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. option-data .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code OPTION_V-I VENDOR_OPTS (to be assigned by
IANA)
option-len 4 + length of option-data field
enterprise-number The vendor's registered Enterprise Number as
registered with IANA [4].
option-data Encapsulated vendor-specific options,
described below.
The definition of the information carried in this option is vendor
specific. The vendor is indicated in the enterprise-number field.
Each instance of this option contains information corresponding to a
single Enterprise Number. Multiple instances of this option may be
present, and each is treated independently.
Use of vendor-specific information allows enhanced operation,
utilizing additional features in a vendor's DHCP implementation.
Servers not equipped to interpret the vendor-specific information
sent by a client MUST ignore it. Clients that do not receive desired
vendor-specific information SHOULD make an attempt to operate without
it.
The encapsulated vendor-specific options field MUST be encoded as a
sequence of code/length/value fields of identical format to the DHCP
options field. The option codes are defined by the vendor identified
in the enterprise-number field and are not managed by IANA. Option
codes 0 and 255 have no pre-defined interpretation or format. Each
of the encapsulated options is formatted as follows:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| opt-code | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. option-data .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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opt-code The code for the encapsulated option
option-len An unsigned integer giving the length of the
option-data field in this encapsulated option
in octets.
option-data The data area for the encapsulated option
Multiple instances of the Vendor-specific Information option may
appear in a DHCP message. Each instance of the option is interpreted
according to the option codes defined by the vendor identified by the
Enterprise Number in that option.
4. IANA Considerations
The values for the V-I VENDOR CLASS and V-I VENDOR OPTS option codes
must be assigned from the numbering space defined for public DHCP
Options in RFC 2939 [5].
5. Security Considerations
This document in and by itself provides no security, nor does it
impact existing security. DHCP provides an authentication and
message integrity mechanism, as described in RFC 3118 [6], which may
be used if authenticity is required for data carried by the options
defined in this document.
References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] S. Alexander and R. Droms. "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.
[3] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and
Carney, M., "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", RFC 3315, July 2003.
[4] IANA. Private Enterprise Numbers.
http://www.iana.org/assignments/enterprise-numbers.html.
[5] Droms, R., "Procedures and IANA Guidelines for Definition of New
DHCP Options and Message Types", BCP 43, RFC 2939, September
2000.
[6] Droms, R. and W. Arbaugh, "Authentication for DHCP Messages", RFC
3118, June 2001.
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Author's Address
Josh Littlefield
Cisco Systems, Inc.
1414 Massachusetts Avenue
Boxborough, MA 01719 USA
Phone: 978-936-1379
Email: joshl@cisco.com
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Acknowledgement
Funding for the RFC editor function is currently provided by the
Internet Society.
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