Internet DRAFT - draft-halwasia-dhc-dhcpv6-hardware-addr-opt
draft-halwasia-dhc-dhcpv6-hardware-addr-opt
Network Working Group G. Halwasia
Internet-Draft S. Bhandari
Intended status: Standards Track W. Dec
Expires: September 13, 2012 Cisco Systems
March 12, 2012
Client Link-layer Address Option in DHCPv6
draft-halwasia-dhc-dhcpv6-hardware-addr-opt-01
Abstract
This document specifies the format and mechanism that is to be used
for encoding client link-layer address in DHCPv6 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.
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This Internet-Draft will expire on September 13, 2012.
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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 Client Behavior . . . . . . . . . . . . . . . . . . . . 4
5. DHCPv6 Relay Agent Behavior . . . . . . . . . . . . . . . . . . 4
6. DHCPv6 Server Behavior . . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
10. Change History (to be removed prior to publication as an
RFC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
11. Normative References . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
This specification defines an optional mechanism and the related
DHCPv6 option to allow DHCPv6 client or 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,
effectievly an enablement of dual-stack, there will be devices that
act as both DHCPv4 and DHCPv6 clients. In service provider
deployments, a typical DHCPv4 implemention 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 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 client
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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 Client Behavior
All hosts or clients MAY include DHCPv6 Client link-layer address
option in all the upstream DHCPv6 messages.
5. DHCPv6 Relay Agent Behavior
DHCPv6 Relay agents which are directly connected to clients/hosts MAY
look for Client Link-layer Address option in the incoming DHCPv6
client message. Irrespective of the presence of client link-layer
option in incomming DHCPv6 client messages, DHCPv6 Relay agents 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.
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In Relay chaining scenarios, any other relay agent other than first
hop DHCPv6 Relay agent or DHCPv6 LDRA [RFC6221] MUST not add this
option.
6. DHCPv6 Server Behavior
If DHCPv6 Server is configured to store or use client link-layer
address, it SHOULD first look for the client link-layer address
option in the RELAY-FORW DHCP message of the DHCPv6 Relay agent
closest to the client. In case it is not found, Server SHOULD look
for client link-layer address option in the client DHCP message.
Further, this behavior w.r.t the precedence of DHCPv6 server to look
for Client link-layer address option can be overridden based upon the
local policies.
There is no requirement that a server return this option and its data
in a downstream DHCP message.
7. 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).
8. Security Considerations
Security issues related DHCPv6 are described in section 23 of
[RFC3315].
9. Acknowledgements
Many thanks to Bernie Volz, Hemant Singh, Simon Hobson, Tina TSOU,
Andre Kostur, Chuck Anderson, Steinar Haug, Niall O'Reilly, Jarrod
Johnson and Vincent Zimmer for their input and review.
10. Change History (to be removed prior to publication as an RFC)
Changes from -00 to -01
a. "hardware address" has been renamed to "Link-layer address" to be
consistent with DHCPv6 terminology
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b. 1 byte chtype in DHCPv6 Client Link-layer Address option is
replaced with 2 byte hardware type
c. chaddr in DHCPv6 Client Link-layer Address option is renamed as
link-layer address
11. 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.
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
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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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