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Versions: 00 01 02 03 04 05 RFC 6939

Network Working Group                                        G. Halwasia
Internet-Draft                                               S. Bhandari
Intended status: Standards Track                                  W. Dec
Expires: February 15, 2013                                 Cisco Systems
                                                         August 14, 2012


               Client Link-layer Address Option in DHCPv6
          draft-ietf-dhc-dhcpv6-client-link-layer-addr-opt-01

Abstract

   This document specifies the format and mechanism that is to be used
   for encoding client link-layer address in DHCPv6 relay forward
   messages by defining a new DHCPv6 Client Link-layer Address option.

Requirements Language

   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 [RFC2119].

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on February 15, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Problem Background and Scenario . . . . . . . . . . . . . . . . 3
   3.  DHCPv6 Client Link-layer Address Option . . . . . . . . . . . . 4
   4.  DHCPv6 Relay Agent Behavior . . . . . . . . . . . . . . . . . . 4
   5.  DHCPv6 Server Behavior  . . . . . . . . . . . . . . . . . . . . 4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 5
   9.  Normative References  . . . . . . . . . . . . . . . . . . . . . 5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 6
































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1.  Introduction

   This specification defines an optional mechanism and the related
   DHCPv6 option to allow first hop DHCPv6 relay agent directly
   connected to the client to populate client link-layer address in the
   DHCPv6 messages being sent towards the server.


2.  Problem Background and Scenario

   DHCPv4 protocol specification [RFC2131] provides a way to specify the
   client hardware address in the DHCPv4 message header.  DHCPv4 message
   header has 'htype' and 'chaddr' fields to specify client hardware
   address type and hardware address respectively.  The client hardware
   address thus learnt can be used by DHCPv4 server and relay in
   different ways.  In some of the deployments DHCPv4 servers use
   'chaddr' as a customer identifier and a key for lookup in the client
   lease database.

   With the incremental deployment of IPv6 to existing IPv4 networks,
   effectively an enablement of dual-stack, there will be devices that
   act as both DHCPv4 and DHCPv6 clients.  In service provider
   deployments, a typical DHCPv4 implementation will use the client
   hardware address as one of the keys to build DHCP client lease
   database.  In dual stack scenarios it is desirable for the operator
   to associate DHCPv4 and DHCPv6 messages as belonging to the same
   client interface based on an identifier that is already used by that
   operator such as the client hardware address.

   Currently, the DHCPv6 protocol specification [RFC3315] does not
   define a way for DHCP clients to specify client link-layer address in
   the DHCPv6 message sent towards DHCPv6 Server.  Similarly DHCPv6
   Relay or Server cannot glean client link-layer address from the
   contents of DHCPv6 message received.  DHCPv6 protocol specification
   mandates all clients to prepare and send DUID as the client
   identifier option in all the DHCPv6 message exchange.  However none
   of these methods provide a simple way to extract client's link-layer
   address.This presents a problem to an operator who is using an
   existing DHCPv4 system with the client hardware address as the
   customer identifier, and desires to correlate DHCPv6 assignments
   using the same identifier.  Modifying the system to use DUID based
   correlation across DHCPv4 and DHCPv6 is possible, but it requires a
   modification of the DHCPv4 system and associated back-ends.

   Providing an option in DHCPv6 relay forward messages to carry client
   link-layer address explicitly will help above mentioned scenarios.
   For e.g. it can be used along with other identifiers to associate
   DHCPv4 and DHCPv6 messages from a dual stack client.  Further, having



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   client link-layer address in DHCPv6 will help in proving additional
   information in event debugging and logging related to the client at
   relay and server.  The proposed option may be used in wide range of
   networks, two notable deployment models are service provider and
   enterprise network environments.


3.  DHCPv6 Client Link-layer Address Option

   The format of the DHCPv6 Client Link-layer Address option is shown
   below.
    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | OPTION_CLIENT_LINKLAYER_ADDR  |           option-length       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    hardware type (16 bits)    |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
   |               link-layer address (variable length)            |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   option-code:        OPTION_CLIENT_LINKLAYER_ADDR (TBD)
   option-length:      2 + length of link-layer address
   hardware type:      Client Link-layer address type. The hardware type MUST be a
                       valid hardware type assigned by the IANA, as described in [RFC0826]
   link-layer address: Client Link-layer address.



4.  DHCPv6 Relay Agent Behavior

   DHCPv6 Relay agents which are directly connected to clients/hosts MAY
   include client link-layer address option in relayed DHCPv6 (RELAY-
   FORW) message.  The DHCPv6 Relay agent behaviour can depend on
   configuration that decides whether Client Link-layer Address option
   needs to be processed and included.

   In Relay chaining scenarios, any other relay agent other than first
   hop DHCPv6 Relay agent or DHCPv6 LDRA [RFC6221] MUST not add this
   option.


5.  DHCPv6 Server Behavior

   If DHCPv6 Server is configured to store or use client link-layer



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   address, it SHOULD look for the client link-layer address option in
   the RELAY-FORW DHCP message of the DHCPv6 Relay agent closest to the
   client.

   There is no requirement that a server return this option and its data
   in a downstream DHCP message.


6.  IANA Considerations

   IANA is requested to assign an option code to
   OPTION_CLIENT_LINKLAYER_ADDR from the "DHCPv6 and DHCPv6 options"
   registry (http://www.iana.org/assignments/dhcpv6-parameters/dhcpv6-
   parameters.xml).


7.  Security Considerations

   Security issues related DHCPv6 are described in section 23 of
   [RFC3315].


8.  Acknowledgements

   Many thanks to Bernie Volz, Hemant Singh, Simon Hobson, Tina TSOU,
   Andre Kostur, Chuck Anderson, Steinar Haug, Niall O'Reilly, Jarrod
   Johnson, Tomek Mrugalski and Vincent Zimmer for their input and
   review.


9.  Normative References

   [RFC0826]  Plummer, D., "Ethernet Address Resolution Protocol: Or
              converting network protocol addresses to 48.bit Ethernet
              address for transmission on Ethernet hardware", STD 37,
              RFC 826, November 1982.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
              RFC 2131, March 1997.

   [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.

   [RFC6221]  Miles, D., Ooghe, S., Dec, W., Krishnan, S., and A.



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              Kavanagh, "Lightweight DHCPv6 Relay Agent", RFC 6221,
              May 2011.


Authors' Addresses

   Gaurav Halwasia
   Cisco Systems
   Cessna Business Park, Sarjapura Marathalli Outer Ring Road
   Bangalore, KARNATAKA  560 087
   India

   Phone: +91 80 4426 1321
   Email: ghalwasi@cisco.com


   Shwetha Bhandari
   Cisco Systems
   Cessna Business Park, Sarjapura Marathalli Outer Ring Road
   Bangalore, KARNATAKA  560 087
   India

   Phone: +91 80 4426 0474
   Email: shwethab@cisco.com


   Wojciech Dec
   Cisco Systems
   Haarlerbergweg 13-19
   1101 CH Amsterdam, Amsterdam  560 087
   The Netherlands

   Email: wdec@cisco.com


















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