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Versions: 00 01 02 03 RFC 3925
DHC Working Group J. Littlefield
Internet-Draft Cisco Systems, Inc.
Expires: November 17, 2004 May 17, 2004
Vendor-Identifying Vendor Options for DHCPv4
draft-ietf-dhc-vendor-02.txt
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Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
The DHCP options for Vendor Class and Vendor-Specific Information can
be limiting or 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
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document are to be interpreted as described in RFC 2119 [1].
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Supporting Multiple Vendor Instances . . . . . . . . . . . . . 3
3. Vendor-Identifying Vendor Class Option . . . . . . . . . . . . 4
4. Vendor-Identifying Vendor-Specific Information Option . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1 Normative References . . . . . . . . . . . . . . . . . . . . 8
7.2 Informative References . . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . 9
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1. Introduction
The DHCP protocol for IPv4, RFC 2131 [2], defines options that 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) [5]. 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. Furthermore, the
concatenation of multiple instances of the same option, required by
RFC 2131 and specified by RFC 3396 [4], means that multiple copies of
options 60 or 43 would not remain independent.
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 [9] 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 defined in RFC 3315
[6], which contain Enterprise Numbers to remove ambiguity about the
interpretation of their contents. 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. Supporting Multiple Vendor Instances
The options defined in this document may each contain data
corresponding to more than one vendor. The data portion of each
option defined here contains an enterprise number, followed by an
internal data length, followed by vendor-specific data. This
sequence may be repeated multiple times within each option. Because
of the possibility that the aggregate of the vendor-specific data for
either option will exceed 255 octets, these options are hereby
declared to be "concatenation-requiring", as defined by RFC 3396 [4].
As such, the aggregate of all instances of vendor-specific data is to
be considered one long option, for each of the two options defined
here. These long options can be divided into smaller options for
packet encoding in conformance with RFC 3396, on whatever octet
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boundaries are convenient to the implementation. Dividing on the
boundaries between vendor instances is not required, but may be
convenient for encoding or packet tracing.
3. 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,
the software in use, or an industry consortium to which the vendor
belongs. The information contained in the per-vendor data area of
this option is contained in one or more opaque fields that may
identify details of the hardware configuration.
This option may be used wherever Vendor Class Identifier (option 60)
may be used, as described in RFC 2131 [2], except for DHCPNAK
messages, where other options are not permitted. It is most
meaningful in messages from DHCP client to DHCP server (DHCPDISCOVER,
DHCPREQUEST, DHCPINFORM).
The format of the V-I Vendor Class option is:
1 1 1 1 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-code | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| enterprise-number1 |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| data-len1 | |
+-+-+-+-+-+-+-+-+ |
/ vendor-class-data1 /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----
| enterprise-number2 | ^
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| data-len2 | | optional
+-+-+-+-+-+-+-+-+ | |
/ vendor-class-data2 / |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
~ ... ~ V
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----
option-code OPTION_V-I_VENDOR_CLASS (to be assigned by IANA)
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option-len 5 + length of vendor class data field
enterprise-numberN The vendor's 32-bit Enterprise Number as
registered with IANA [3]
data-lenN Length of vendor-class-data field
vendor-class-dataN Details of the hardware configuration of the
host on which the client is running, or of
industry consortium compliance
This option contains information corresponding to one or more
Enterprise Numbers. Multiple instances of this option may be
present, and MUST be concatenated in accordance with RFC 3396 [4].
An Enterprise Number SHOULD only occur once among all instances of
this option. Behavior is undefined if an Enterprise Number occurs
multiple times. The information for each Enterprise Number is
treated independently, regardless or whether it occurs in an option
with other Enterprise Numbers, or in a separate option.
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:
1 1 1 1 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| data-len | |
+-+-+-+-+-+-+-+-+ opaque-data |
/ /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The data-len is one octet long and specifies the length of the opaque
vendor class data in network byte order.
4. Vendor-Identifying Vendor-Specific Information Option
DHCP clients and servers may use this option to exchange vendor-
specific information. Either party may send this option, as needed.
While a typical case might be for a client to send the
Vendor-Identifying Vendor Class option, to elicit a useful
Vendor-Identifying Vendor-Specific Information Option, there is no
requirement for such a flow.
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This option may be used in any packets where "other" options are
allowed by RFC2131 [2], specifically DHCPDISCOVER, DHCPOFFER,
DHCPREQUEST, DHCPACK and DHCPINFORM.
The format of the V-I Vendor-specific Information option is:
1 1 1 1 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-code | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| enterprise-number1 |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| data-len1 | |
+-+-+-+-+-+-+-+-+ option-data1 |
/ /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----
| enterprise-number2 | ^
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| data-len2 | | optional
+-+-+-+-+-+-+-+-+ option-data2 | |
/ / |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
~ ... ~ V
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----
option-code OPTION_V-I_VENDOR_OPTS (to be assigned by IANA)
option-len 5 + length of option-data field
enterprise-numberN The vendor's registered 32-bit Enterprise Number
as registered with IANA [3]
data-lenN Length of option-data field
option-dataN 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.
This option contains information corresponding to one or more
Enterprise Numbers. Multiple instances of this option may be
present, and MUST be concatenated in accordance with RFC 3396 [4].
An Enterprise Number SHOULD only occur once among all instances of
this option. Behavior is undefined if an Enterprise Number occurs
multiple times. The information for each Enterprise Number is
treated independently, regardless or whether it occurs in an option
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with other Enterprise Numbers, or in a separate option.
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 option-data 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:
1 1 1 1 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| subopt-code | subopt-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ sub-option-data /
/ /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
subopt-code The code for the encapsulated option
subopt-len An unsigned integer giving the length of the
option-data field in this encapsulated option in
octets
sub-option-data Data area for the encapsulated option
5. IANA Considerations
The values for the OPTION_V-I_VENDOR_CLASS and OPTION_V-I_VENDOR_OPTS
option codes must be assigned from the numbering space defined for
public DHCP Options in RFC 2939 [7].
6. 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 [8], which may
be used if authenticity is required for data carried by the options
defined in this document.
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7. References
7.1 Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997.
[3] IANA, "Private Enterprise Numbers",
<http://www.iana.org/assignments/enterprise-numbers.html>.
[4] Lemon, T. and S. Chesire, "Encoding Long Options in the Dynamic
Host Configuration Protocol (DHCPv4)", RFC 3396, November 2002.
7.2 Informative References
[5] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.
[6] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and M.
Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 3315, July 2003.
[7] Droms, R., "Procedures and IANA Guidelines for Definition of New
DHCP Options and Message Types", BCP 43, RFC 2939, September
2000.
[8] Droms, R. and W. Arbaugh, "Authentication for DHCP Message", RFC
3118, June 2001.
URIs
[9] <http://www.cablelabs.com/>
Author's Address
Josh Littlefield
Cisco Systems, Inc.
1414 Massachusetts Avenue
Boxborough, MA 01719
USA
Phone: +1 978-936-1379
EMail: joshl@cisco.com
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