DHC Working Group                                               M. Stapp
Internet-Draft                                                R. Johnson
Expires: January 6, 2005                                  T. Palaniappan
                                                     Cisco Systems, Inc.
                                                            July 8, 2004


 Vendor-Specific Information Suboption for the DHCP Relay Agent Option
               <draft-stapp-dhc-vendor-suboption-01.txt>

Status of this Memo

   By submitting this Internet-Draft, I certify that any applicable
   patent or other IPR claims of which I am aware have been disclosed,
   and any of which I become aware will be disclosed, in accordance with
   RFC 3667.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
   groups may also distribute working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at http://
   www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on January 6, 2005.

Copyright Notice

   Copyright (C) The Internet Society (2004). All Rights Reserved.

Abstract

   This memo defines a new Vendor-Specific Information suboption for the
   Dynamic Host Configuration Protocol's (DHCP) relay agent information
   option. The suboption allows a DHCP relay agent to include
   vendor-specific information in DHCP messages it forwards, as
   configured by its administrator.







Stapp, et al.           Expires January 6, 2005                 [Page 1]


Internet-Draft         Vendor-Specific Suboption               July 2004


Table of Contents

   1. Requirements Terminology . . . . . . . . . . . . . . . . . . . . 3
   2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3. The Vendor-Specific Suboption  . . . . . . . . . . . . . . . . . 3
   4. Relay Agent Behavior . . . . . . . . . . . . . . . . . . . . . . 4
   5. DHCP Server Behavior . . . . . . . . . . . . . . . . . . . . . . 5
   6. Security Considerations  . . . . . . . . . . . . . . . . . . . . 5
   7. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . . 6
   8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 6
      Normative References . . . . . . . . . . . . . . . . . . . . . . 7
      Informative References . . . . . . . . . . . . . . . . . . . . . 7
      Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
      Intellectual Property and Copyright Statements . . . . . . . . . 9





































Stapp, et al.           Expires January 6, 2005                 [Page 2]


Internet-Draft         Vendor-Specific Suboption               July 2004


1. Requirements Terminology

   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].

2. Introduction

   DHCP (RFC 2131 [2]) provides IP addresses and configuration
   information for IPv4 clients. It includes a relay agent capability,
   in which processes within the network infrastructure receive
   broadcast messages from clients and forward them to DHCP servers as
   unicast messages. In network environments like DOCSIS data-over-cable
   and xDSL, for example, it has proven useful for the relay agent to
   add information to the DHCP message before forwarding it, using the
   relay agent information option (RFC 3046 [3]).

   Servers that recognize the relay agent option echo it back in their
   replies, and some of the information that relays add may be used to
   help an edge device efficiently return replies to clients. The
   information that relays supply can also be used in the server's
   decision making about the addresses and configuration parameters that
   the client should receive.

   In many environments it's desirable to associate some vendor- or
   provider-specific information with clients' DHCP messages. This is
   often done using the relay agent information option. RFC 3046 defines
   Remote-ID and Circuit-ID sub-options that are used to carry such
   information. The values of those suboptions, however, are usually
   based on some network resource, such as an IP address of a network
   access device, an ATM Virtual Circuit identifier, or a DOCSIS
   cable-modem identifier. As a result, the values carried in these
   suboptions are dependent on the physical network configuration. The
   Vendor-Specific suboption allows administrators to associate other
   useful data with relayed DHCP messages.

3. The Vendor-Specific Suboption

   This memo defines a new DHCP relay agent option suboption that
   carries vendor-defined data. The suboption takes a form similar to
   the Vendor-Identifying Vendor-Specific Option [8].










Stapp, et al.           Expires January 6, 2005                 [Page 3]


Internet-Draft         Vendor-Specific Suboption               July 2004


       0                   1                   2                   3
       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Code      |    Length     |        Enterprise Number1     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               |  DataLen1     |               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               +
      \                         Suboption Data1                       \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Enterprise Number2                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  DataLen2     |             Suboption Data2                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      \                                                               \
      .                                                               .
      .                                                               .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The Code for the suboption is <TBD> (to be assigned by IANA).

   The one-byte Length field is the length of the data carried in the
   suboption, in bytes. The length includes the length of the first
   Enterprise Number; the minimum length is 4 bytes.

   "Enterprise NumberN" is a vendor's Enterprise Number as registered
   with IANA [4]. It is a four-byte integer value in network byte-order.

   DataLenN is the length of the data associated with the Enterprise
   Number.

   The Suboption Data is an opaque sequence of bytes.

   The Vendor-Specific suboption includes at least one Enterprise Number
   and carries opaque data defined by the organization identified by the
   Enterprise Number. A relay may include data associated with more than
   one vendor's Enterprise Number within a single instance of the
   Suboption.

   The Vendor-Specific data are of course provider-specific. This
   specification does not establish any requirements on the data in the
   suboption. Vendors who make use of this suboption are encouraged to
   document their usage in order to make interoperability possible.

4. Relay Agent Behavior

   DHCP relay agents MAY be configured to include Vendor-Specific
   suboptions if they include a relay agent information option in



Stapp, et al.           Expires January 6, 2005                 [Page 4]


Internet-Draft         Vendor-Specific Suboption               July 2004


   relayed DHCP messages. The suboptions' types and data are assigned
   and configured through mechanisms that are outside the scope of this
   memo.

   Relay implementors are encouraged to offer their administrators some
   means of configuring what data can be included in this suboption, and
   to document what they are capable of.

5. DHCP Server Behavior

   This suboption provides additional information to the DHCP server.
   The DHCP server, if it is configured to support this suboption, may
   use this information in addition to other relay agent option data and
   other options included in the DHCP client messages in order to assign
   an IP address and/or other configuration parameters to the client.
   There is no special additional processing for this suboption.

   DHCP server vendors are encouraged to offer their administrators some
   means of configuring the use of data from incoming Vendor-Specific
   suboptions in DHCP decision-making.

6. Security Considerations

   Message authentication in DHCP for intradomain use where the
   out-of-band exchange of a shared secret is feasible is defined in RFC
   3118 [5]. Potential exposures to attack are discussed in section 7 of
   the DHCP protocol specification in RFC 2131 [2].

   The DHCP relay agent option depends on a trusted relationship between
   the DHCP relay agent and the server, as described in section 5 of RFC
   3046. Fraudulent relay agent option data could potentially lead to
   theft-of-service or exhaustion of limited resources (like IP
   addresses) by unauthorized clients. A host that tampered with relay
   agent data associated with another host's DHCP messages could deny
   service to that host, or interfere with its operation by leading the
   DHCP server to assign it inappropriate configuration parameters.

   While the introduction of fraudulent relay agent options can be
   prevented by a perimeter defense that blocks these options unless the
   relay agent is trusted, a deeper defense using authentication for
   relay agent options via the Authentication Suboption [6] or IPSEC [7]
   SHOULD be deployed as well.

   There are several data in a DHCP message that convey information that
   may identify an individual host on the network. These include the
   chaddr, the client-id option, and the hostname and client-fqdn
   options. Depending on the type of data included, the Vendor-Specific
   suboption may also convey information that identifies a specific host



Stapp, et al.           Expires January 6, 2005                 [Page 5]


Internet-Draft         Vendor-Specific Suboption               July 2004


   or a specific user on the network. In practice, this information
   isn't exposed outside the internal service-provider network, where
   DHCP messages are usually confined. Administrators who configure data
   that's going to be used in DHCP Vendor-Specific suboptions should be
   careful to use data that are appropriate for the types of networks
   they administer. If DHCP messages travel outside the
   service-provider's own network, or if the suboption values may become
   visible to other users, that may raise privacy concerns for the
   access provider or service provider.

7. IANA Considerations

   IANA is requested to assign a suboption number for the
   Vendor-Specific Information Suboption from the DHCP Relay Agent
   Information Option [3] suboption number space.

8. Acknowledgements

   The authors are grateful to Andy Sudduth, Josh Littlefield, and Kim
   Kinnear for their review and comments.































Stapp, et al.           Expires January 6, 2005                 [Page 6]


Internet-Draft         Vendor-Specific Suboption               July 2004


Normative References

   [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", RFC 2119, March 1997.

   [2]  Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
        March 1997.

   [3]  Patrick, M., "DHCP Relay Agent Information Option", RFC 3046,
        January 2001.

   [4]  IANA, "Private Enterprise Numbers (http://www.iana.org/
        assignments/enterprise-numbers.html)".

Informative References

   [5]  Droms, R. and W. Arbaugh, "Authentication for DHCP Messages",
        RFC 3118, June 2001.

   [6]  Stapp, M., "The Authentication Suboption for the DHCP Relay
        Agent Option", draft-ietf-dhc-auth-suboption-04.txt  (work in
        progress), October 2003.

   [7]  Droms, R., "Authentication of Relay Agent Options Using IPsec",
        draft-ietf-dhc-relay-agent-ipsec-01.txt  (work in progress),
        November 2003.

   [8]  Littlefield, J., "Vendor-Identifying Vendor Options for DHCPv4",
        draft-ietf-dhc-vendor-02.txt  (work in progress), November 2004.


Authors' Addresses

   Mark Stapp
   Cisco Systems, Inc.
   1414 Massachusetts Ave.
   Boxborough, MA  01719
   USA

   Phone: 978.936.0000
   EMail: mjs@cisco.com










Stapp, et al.           Expires January 6, 2005                 [Page 7]


Internet-Draft         Vendor-Specific Suboption               July 2004


   Richard Johnson
   Cisco Systems, Inc.
   170 W. Tasman Dr.
   San Jose, CA  95134
   USA

   Phone: 408.526.4000
   EMail: raj@cisco.com


   Theyn Palaniappan
   Cisco Systems, Inc.
   170 W. Tasman Dr.
   San Jose, CA  95134
   USA

   Phone: 408.526.4000
   EMail: athenmoz@cisco.com

































Stapp, et al.           Expires January 6, 2005                 [Page 8]


Internet-Draft         Vendor-Specific Suboption               July 2004


Intellectual Property Statement

   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.


Disclaimer of Validity

   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.


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.


Acknowledgment

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




Stapp, et al.           Expires January 6, 2005                 [Page 9]