Client-Inserted Client Link-Layer Address Options in DHCPv6
draft-templin-client-cllao-00

Network Working Group                                    F. Templin, Ed.
Internet-Draft                              Boeing Research & Technology
Intended status: Informational                          January 21, 2015
Expires: July 25, 2015

      Client-Inserted Client Link-Layer Address Options in DHCPv6
                   draft-templin-client-cllao-00.txt

Abstract

   RFC6939 presents a method for DHCPv6 relay agents to insert a Client
   Link Layer Address Option (CLLAO) in a DHCPv6 Relay-Forward message.
   In some cases, however, the DHCPv6 client may need to insert a CLLAO
   in its message on its own behalf even though it is on the same link
   as the DHCPv6 server.  This document discusses client-inserted
   CLLAOs.

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Client-Inserted CLLAOs  . . . . . . . . . . . . . . . . . . .   2
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   3
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   3
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   3
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   4

1.  Introduction

   [RFC6939] specifies a method for DHCPv6 relays[RFC3315] to insert a
   Client Link-Layer Address Option (CLLAO) in Relay-Forward messages.
   This provides a means for a first-hop relay to inform the DHCPv6
   server of the link-layer address of the DHCPv6 client on the
   client<->relay link.  However, on some links it may be necessary for
   the server to receive a CLLAO even when it is on the same link as the
   client.  In that case, the client itself must insert the CLLAO.

   Asymmetric Extended Route Optimization (AERO) [I-D.templin-aerolink]
   is an example of a link where it may be difficult or impossible for
   the DHCPv6 server to determine the DHCPv6 client's link-layer address
   through normal socket API operations.  In that case, if the client
   inserts a CLLAO option the server can discover the client's link-
   layer address by examining the option fields of the DHCPv6 message
   instead of the message headers.  The following section specifies the
   protocol for client-inserted CLLAOs.

2.  Client-Inserted CLLAOs

   When a DHCPv6 client is on the same link as the server, and the
   server requires a means for discovering the client's link-layer
   address, the client inserts a CLLAO option [RFC6939] in its DHCPv6
   messages and writes the link-layer address of the sending interface
   in the "link-layer address" field.

   When a DHCPv6 server is on the same link as the client, and the
   client includes a CLLAO option in its DHCPv6 messages, the server
   processes the CLLAO option locally as necessary and returns the CLLAO
   option in its DHCPv6 replies.

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   When a DHCPv6 relay on the same link as a client forwards the
   client's DHCPv6 messages, and the server requires a means for
   discovering the client's link-layer address, the relay follows the
   specifications in [RFC6939].

   A DHCPv6 client MUST NOT include a CLLAO option if it is not on the
   same link as the server.

3.  IANA Considerations

   This document introduces no IANA considerations.

4.  Security Considerations

   When DHCPv6 authentication [RFC3315] and/or DHCPv6 Security
   [I-D.ietf-dhc-sedhcpv6] are used, the DHCPv6 client/server MUST NOT
   include the CLLAO option in security signature calculations.  This
   means that the link-layer address in the CLLAO could be rewritten by
   a link-layer switching element on the path from the client to the
   server and not detected by the security mechanism.  However, such a
   condition would only be possible on unsecured links where link-layer
   switching elements present a man-in-the-middle attack threat.

5.  Acknowledgements

6.  References

6.1.  Normative References

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC6939]  Halwasia, G., Bhandari, S., and W. Dec, "Client Link-Layer
              Address Option in DHCPv6", RFC 6939, May 2013.

6.2.  Informative References

   [I-D.ietf-dhc-sedhcpv6]
              Jiang, S., Shen, S., Zhang, D., and T. Jinmei, "Secure
              DHCPv6", draft-ietf-dhc-sedhcpv6-05 (work in progress),
              December 2014.

   [I-D.templin-aerolink]
              Templin, F., "Transmission of IP Packets over AERO Links",
              draft-templin-aerolink-50 (work in progress), December
              2014.

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Author's Address

   Fred L. Templin (editor)
   Boeing Research & Technology
   P.O. Box 3707
   Seattle, WA  98124
   USA

   Email: fltemplin@acm.org

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