Network Working Group B. Sarikaya
Internet-Draft F. Xia
Expires: September 11, 2008 Huawei USA
March 10, 2008
Relay Based DHCPv6 Prefix Delegation for NEMO
draft-sarikaya-mext-relay-dhcpv6pd-00.txt
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Abstract
This document defines DHCP Relay Agent based prefix delegation
support for a mobile network. Mobile Router uses DHCPv6 prefix
delegation to dynamically request its Mobile Network Prefixes from
DHCP Server. DHCP Relay Agent located in MR enables MR to run the
prefix delegation application with the same DHCP Server even after MR
moves to a different local network.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Nemo Prefix Delegation Architecture . . . . . . . . . . . . . . 3
3.1. Message Encapsulation . . . . . . . . . . . . . . . . . . . 4
4. Nemo Prefix Delegation Protocol . . . . . . . . . . . . . . . . 5
5. Nemo Prefix Delegation Using AAA . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . . 7
9.2. Informative references . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . . . 9
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1. Introduction
Nemo Basic Support Protocol requires that IPv6 prefixes called Home
Network Prefix(es) delegated to a Mobile Router and advertized in the
Mobile Network [RFC3963]. However the protocol does not provide any
means of provisioning MNPs dynamically.
Prefix delegation is widely discussed in IETF 16NG, MEXT, and NETLMM
Working Groups. Corresponding solutions are also introduced. NEMO
deals with synchronization of Mobile Network prefixes between a
Mobile Router and a Home Agent, while the method is agnostic to the
way that a Home Agent gets prefixes from back end servers.
[RFC3633] defines Prefix Delegation options and procedures to provide
a mechanism for automated delegation of IPv6 prefixes using the
Dynamic Host Configuration Protocol (DHCP). A mechanism to manage
prefixes dynamically by an AAA server can also be defined.
[I-D.ietf-nemo-prefix-delegation] defines prefix request option for
the binding update and prefix confirm for the binding acknowledgment
messages of the Nemo Basic Support Protocol. Using these messages MR
can request a prefix from HA with BU and HA can give prefixes to MR
with BA. However, how HA gets prefixes is not defined.
2. Terminology
This document uses the terminology defined in [RFC3315], [RFC3633]
and [RFC4885].
3. Nemo Prefix Delegation Architecture
We assume that the prefixes are managed by an authority that owns the
Home Network and subnets it into MNPs that it assigns to the MRs. An
MNP can be preassigned to the associated MR (e.g. manually or
automatically with a provisioning system).
For dynamic prefix management there are two architectures. In HA-
based architecture, HA is the requesting router and the DHCP Server
is the delegating router. HA needs to be collocated with a DHCP
Client to solicit/request prefixes from the DHCP Server. HA is
configured with the address of the delegating router which is a
backend DHCP Server. MR needs to request dynamically the prefixes
from HA using BU/BA exchange defined in
[I-D.ietf-nemo-prefix-delegation].
In MR-based architecture, MR is the requesting router and the
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delegating router is a DHCP Server located in the home network. In
this document, we elaborate on the signaling required for this
architecture.
[I-D.ietf-nemo-dhcpv6-pd] uses the MR-based architecture but it does
not incorporate a DHCP Relay at the MR. [I-D.ietf-nemo-dhcpv6-pd]
assumes a DHCP Client at the MR which requires an onlink DHCP Relay
or Server [I-D.dupont-mext-dhcrelay]. However when MR moves it is
not possible to satisfy this requirement.
Figure 1 shows the MR-based architecture.
+-----+ HA-MR +-----+ +--------+ --------------
| MR |-- tunnel --| HA |--------+ Edge | / \
+-----+ +-----+ | Router +-- | Backend |
|Relay| |Relay| +--------+ \ /
+-----+ +-----+ -------------
|DHCP |<--- |
|Client| | +------+
+------+ -----DHCP Prefix Delegation------------>|DHCP |
|Server|
+------+
Figure 1: MR-based Architecture
MR is co-located with DHCP Relay Agent. In order to run DHCP Prefix
Delegation we also need a local DHCP Client at the MR. DHCP Client
will initiate or respond to DHCP messages required for the MR to be
the requesting router.
DHCP Relay co-located with MR will relay the client's messages back
and forth. DHCP Relay co-located at HA will be configured with the
backend DHCP Server's address. The backend DHCP Server will be the
delegating router.
3.1. Message Encapsulation
DHCP Relay co-located at the MR encapsulates DHCP Client's messages
in the form of DHCPv6 datagrams. These datagrams need to be sent
over HA-MR tunnel when MR is not on the home link. This requires
that each such message is piggybacked in a Binding Update message
sent from MR to HA.
IPv6 extension headers for each message sent by the DHCP Relay co-
located at MR MUST contain the mobility header as described in
Section 6.1 of [RFC3775]. MH type MUST be set to 5 for Binding
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Update. The payload MUST contain the DHCP message being sent.
DHCP Relay co-located at the HA encapsulates DHCP Prefix Delegation
messages to be sent in the form of DHCPv6 datagrams. These datagrams
need to be sent over HA-MR tunnel to the MR. This requires that each
such message is piggybacked in a Binding Acknowledgement message sent
from HA to MR.
IPv6 extension header for each message sent by the DHCP Relay co-
located at HA towards MR MUST contain the mobility header as
described in Section 6.1 of [RFC3775]. MH type MUST be set to 6 for
Binding Acknowledgement. The payload MUST contain the DHCP message
being sent.
4. Nemo Prefix Delegation Protocol
Figure 2 shows the process that a Mobile Router as the requesting
router requests prefixes from a DHCP Server as the delegating router
using DHCPv6 [RFC3315] and DHCPv6 Prefix delegation [RFC3633].
MR HA DHCP Server
| |
-->| |1. Trigger to DHCP Client
|2 Relay-forward/Solicit|2. DHCP Relay-Forward/Solicit
|---------------------> |
|3 Relay-reply/Advertise|3. DHCP Relay-reply/ Advertise
|<--------------------- |
|4 Relay-forward/Request|4. DHCP Relay-Forward/Request (MNP)
|---------------------> |
|5 Relay-reply/Reply |5. DHCP Relay-reply/Reply (MNP)
|<--------------------- |
Figure 2: Prefix Delegation in NEMO
1. DHCP Client co-located with MR needs to be triggered to start
requesting prefixes using DHCPv6 Prefix Delegation. The initial
trigger should be when MR boots up. The subsequent triggers are
timeout based. Each prefix received has a lifetime. When the
lifetime of a prefix expires, a trigger SHOULD be received at the
DHCP Client.
2. DHCP Client at the MR initiates DHCP Solicit procedure to request
prefixes for the MN. HA creates and transmits a Solicit message
as described in sections 17.1.1, "Creation of Solicit Messages"
and 17.1.2, "Transmission of Solicit Messages" of RFC 3315. MR
creates an IA_PD and assigns it an IAID. MR MUST include the
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IA_PD option in the Solicit message.
3. The DHCP server sends an Advertise message to MR in the same way
as described in section 17.2.2, "Creation and transmission of
Advertise messages" of RFC 3315.
4. MR uses the same message exchanges as described in section 18,
"DHCP Client-Initiated Configuration Exchange" of RFC 3315 to
obtain or update prefixes from a DHCP server. MR and the DHCP
server use the IA_PD Prefix option to exchange information about
prefixes in much the same way as IA Address options are used for
assigned addresses.
5. MR stores the prefix information it received in the Reply
message.
HA SHOULD add the route to the delegated prefix(es) and advertise the
prefix(es) upstream. HA SHOULD use route aggregation, i.e. advertise
the /48 prefix that is the extension of the delegated /64 prefixes.
In Explicit Mode of NEMO Basic Protocol, MR includes the delegated
prefix(es) to the prefix list in Prefix Information Option of Binding
Update message. This message triggers HA to add a route for the
prefixes included.
5. Nemo Prefix Delegation Using AAA
Diameter prefix delegation application is currently to be defined.
Once such an application is defined, Nemo prefix delegation using
this Diameter application will be included in this section.
6. Security Considerations
This document does not by itself introduce any security issues.
7. IANA Considerations
None.
8. Acknowledgements
TBD.
9. References
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9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999.
[RFC3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
Thubert, "Network Mobility (NEMO) Basic Support Protocol",
RFC 3963, January 2005.
[RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
Host Configuration Protocol (DHCP) version 6", RFC 3633,
December 2003.
[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
in IPv6", RFC 3775, June 2004.
[I-D.ietf-nemo-prefix-delegation]
Kniveton, T. and P. Thubert, "Mobile Network Prefix
Delegation", draft-ietf-nemo-prefix-delegation-02 (work in
progress), August 2007.
[I-D.dupont-mext-dhcrelay]
Dupont, F. and W. Haddad, "DHCPv6 Relay Agents and NEMO",
draft-dupont-mext-dhcrelay-00 (work in progress),
February 2008.
[I-D.ietf-nemo-dhcpv6-pd]
Droms, R. and P. Thubert, "DHCPv6 Prefix Delegation for
NEMO", draft-ietf-nemo-dhcpv6-pd-03 (work in progress),
December 2007.
9.2. Informative 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.
[RFC4885] Ernst, T. and H-Y. Lach, "Network Mobility Support
Terminology", RFC 4885, July 2007.
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Authors' Addresses
Behcet Sarikaya
Huawei USA
1700 Alma Dr. Suite 500
Plano, TX 75075
Phone: +1 972-509-5599
Email: sarikaya@ieee.org
Frank Xia
Huawei USA
1700 Alma Dr. Suite 500
Plano, TX 75075
Phone: +1 972-509-5599
Email: xiayangsong@huawei.com
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