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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

Status of this Memo

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   This Internet-Draft will expire on November 17, 2004.

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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