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).
AbstractThe 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. 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
RFC 2131 , 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) . 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 , 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  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 , that contain IANA-assigned 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. RFC 2119 .
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 . 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. RFC 2131 , 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 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  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 . 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 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. RFC 2131 , specifically DHCPDISCOVER, DHCPOFFER, DHCPREQUEST, DHCPACK, and DHCPINFORM.
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  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 . 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.
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 RFC 2939 . RFC 3118 , which may be used if authenticity is required for data carried by the options defined in this document.
 Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.  Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997.  IANA, "Private Enterprise Numbers", <http://www.iana.org/assignments/enterprise-numbers>.  Lemon, T. and S. Cheshire, "Encoding Long Options in the Dynamic Host Configuration Protocol (DHCPv4)", RFC 3396, November 2002.  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor Extensions", RFC 2132, March 1997.  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003.  Droms, R., "Procedures and IANA Guidelines for Definition of New DHCP Options and Message Types", BCP 43, RFC 2939, September 2000.  Droms, R. and W. Arbaugh, "Authentication for DHCP Messages", RFC 3118, June 2001. http://www.cablelabs.com/>
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