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rfc:rfc3925

Network Working Group J. Littlefield Request for Comments: 3925 Cisco Systems, Inc. Category: Standards Track October 2004

               Vendor-Identifying Vendor Options for
       Dynamic Host Configuration Protocol version 4 (DHCPv4)

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2004).

Abstract

 The Dynamic Host Configuration Protocol (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, that contain Enterprise Numbers to
 remove ambiguity.

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
     1.1.  Conventions Used in This Document. . . . . . . . . . . .  2
 2.  Supporting Multiple Vendor Instances . . . . . . . . . . . . .  3
 3.  Vendor-Identifying Vendor Class Option . . . . . . . . . . . .  3
 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
 8.  Author's Address . . . . . . . . . . . . . . . . . . . . . . .  8
 9.  Full Copyright Statement . . . . . . . . . . . . . . . . . . .  9

Littlefield Standards Track [Page 1] RFC 3925 Vendor-Identifying Vendor Options October 2004

1. Introduction

 The DHCP protocol for IPv4, RFC 2131 [2], defines options that allow
 a client to indicate its vendor type (option 60), and the DHCP client
 and server to exchange vendor-specific information (option 43) [5].
 Although 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.
 In some circumstances, 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, as 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], that contain IANA-assigned Enterprise Numbers [3] 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.

1.1. 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 BCP 14, RFC 2119 [1].

Littlefield Standards Track [Page 2] RFC 3925 Vendor-Identifying Vendor Options October 2004

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 (assigned by IANA
 [3]), followed by an internal data length, followed by vendor-
 specific data.  This sequence may be repeated multiple times within
 each option.  Because the aggregate of the vendor-specific data for
 either option may exceed 255 octets, these options are hereby
 declared to be "concatenation-requiring", as defined by RFC 3396 [4].
 As such, for each of the two options defined here, the aggregate of
 all instances of vendor-specific data is to be considered one long
 option.  These long options can be divided into smaller options for
 packet encoding in conformance with RFC 3396, on whatever octet
 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).

Littlefield Standards Track [Page 3] RFC 3925 Vendor-Identifying Vendor Options October 2004

 The format of the V-I Vendor Class option is as follows:
                      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 (124)
 option-len          total length of all following option data in
                     octets
 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.

Littlefield Standards Track [Page 4] RFC 3925 Vendor-Identifying Vendor Options October 2004

 The vendor-class-data comprises 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.
 Although 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.
 This option may be used in any packets where "other" options are
 allowed by RFC 2131 [2], specifically DHCPDISCOVER, DHCPOFFER,
 DHCPREQUEST, DHCPACK, and DHCPINFORM.

Littlefield Standards Track [Page 5] RFC 3925 Vendor-Identifying Vendor Options October 2004

 The format of the V-I Vendor-specific Information option is as
 follows:
                      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 (125)
 option-len          total length of all following option data in
                     octets
 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
 with other Enterprise Numbers, or in a separate option.

Littlefield Standards Track [Page 6] RFC 3925 Vendor-Identifying Vendor Options October 2004

 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 have been 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.

Littlefield Standards Track [Page 7] RFC 3925 Vendor-Identifying Vendor Options October 2004

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>.
 [4]  Lemon, T. and S. Cheshire, "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 Messages",
      RFC 3118, June 2001.

URIs

 [9]  <http://www.cablelabs.com/>

8. Author's Address

 Josh Littlefield
 Cisco Systems, Inc.
 1414 Massachusetts Avenue
 Boxborough, MA  01719
 USA
 Phone: +1 978-936-1379
 EMail: joshl@cisco.com

Littlefield Standards Track [Page 8] RFC 3925 Vendor-Identifying Vendor Options October 2004

9. Full Copyright Statement

 Copyright (C) The Internet Society (2004).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Intellectual Property

 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the IETF's procedures with respect to rights in IETF Documents can
 be found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at ietf-
 ipr@ietf.org.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Littlefield Standards Track [Page 9]

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