Network Working Group G. Halwasia
Internet-Draft S. Bhandari
Intended status: Standards Track W. Dec
Expires: March 25, 2013 Cisco Systems
September 21, 2012
Client Link-layer Address Option in DHCPv6
draft-ietf-dhc-dhcpv6-client-link-layer-addr-opt-02
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
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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This Internet-Draft will expire on March 25, 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
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publication of this document. Please review these documents
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carefully, as they describe your rights and restrictions with respect
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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 receive messages originating from clients
(for example Solicit and Request, but not, for example, Relay Forward
or Advertise) MAY include the link-layer source address of the
received DHCPv6 message in Client Link-layer Address option in
relayed DHCPv6 Relay Forward messages. The DHCPv6 Relay agent
behavior can depend on configuration that decides whether Client
Link-layer Address option needs to be processed and included.
5. DHCPv6 Server Behavior
If DHCPv6 Server is configured to store or use client link-layer
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
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client. This specification does not specify the mechanism for DHCPv6
Server to find out link-layer address of the directly connected
clients as a DHCP option as it can obtain it directly from the
received message.
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 Ted Lemon, 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.
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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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