One document matched: draft-navali-ip6-over-netmip4-00.txt




Network Working Group                                          J. Navali
Internet-Draft                                              K. Chowdhury
Expires: August 29, 2006                                Starent Networks
                                                       February 25, 2006


                  IPv6 over Network based Mobile IPv4
                  draft-navali-ip6-over-netmip4-00.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
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   This Internet-Draft will expire on August 29, 2006.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   There is a growing demand for routable IP addresses to support large
   wireless user base today.  Wireless operators are looking for ways to
   leverage the IPv6 address space to meet the ever increasing number of
   wireless data users.  The operators who has network based IPv4
   mobility solutions can leverage the same scheme to provide mobility
   access service with larger address pool using IPv6 addressing.  This
   document defines such a mechanism.




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Table of Contents

   1.  Introduction and Scope . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Solution Overview  . . . . . . . . . . . . . . . . . . . . . .  3
     3.1   IPv6 addressing via IPv6CP . . . . . . . . . . . . . . . .  3
       3.1.1   IPv6 Addressing with unique HL prefix  . . . . . . . .  4
       3.1.2   IPv6 Addressing with shared HL prefix  . . . . . . . .  7
     3.2   IPv6 addressing via DHCPv6 . . . . . . . . . . . . . . . . 10
   4.  MIPv4 Message Enhancements . . . . . . . . . . . . . . . . . . 12
     4.1   IPv6 Home Address Request Extension  . . . . . . . . . . . 12
     4.2   IPv6 Home Address Extension  . . . . . . . . . . . . . . . 13
     4.3   MIPv4 Registration Request and Reply . . . . . . . . . . . 14
     4.4   MIPv4 Registration Revocation Procedures . . . . . . . . . 14
   5.  Node Requirements  . . . . . . . . . . . . . . . . . . . . . . 14
     5.1   Mobile Node Requirements . . . . . . . . . . . . . . . . . 15
     5.2   Access Router/NAS/NetMIP4 Client/DHCP-proxy
           Requirements . . . . . . . . . . . . . . . . . . . . . . . 15
       5.2.1   IPv6 Addressing  . . . . . . . . . . . . . . . . . . . 15
       5.2.2   Authentication at the AR . . . . . . . . . . . . . . . 15
       5.2.3   IPv6 Data processing . . . . . . . . . . . . . . . . . 15
     5.3   Home Agent Requirements  . . . . . . . . . . . . . . . . . 15
       5.3.1   IPv6 Addressing  . . . . . . . . . . . . . . . . . . . 15
       5.3.2   Authentication at the HA . . . . . . . . . . . . . . . 16
       5.3.3   IPv6 Data processing . . . . . . . . . . . . . . . . . 16
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 17
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
   9.  Normative References . . . . . . . . . . . . . . . . . . . . . 17
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 18
       Intellectual Property and Copyright Statements . . . . . . . . 19




















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1.  Introduction and Scope

   Mobile operators are running out of routable subscriber IPv4 address
   space and are exploring ways to deploy IPv6 to leverage the expanded
   128-bit address space.  In the absence of native IPv6 support on the
   IPv4 packet core network, a transition mechanism is needed to use the
   IPv6 address space over existing IP core networks.

   This document describes an approach to utilize network based IPv4
   mobility solution to support tunneling of IPv6 traffic from an access
   router to an IPv6 correspondent node via a dual stack home agent.
   The scheme employs MIPv4 messages to obtain an IPv6 Home address
   (HoA) or Home Link (HL) prefix from the home agent so that the access
   router can assign an IPv6 address to an IPv6 mobile node.  The access
   router and the home agent establish an IPv6-over-IPv4 tunnel to carry
   the IPv6 user traffic.  The tunnel is extended to a default 6to4
   gateway configured for the IPv6 address pool on the home agent.  This
   facilitates seamless IPv6 handset mobility across access routers
   while keeping the same IPv6 address.  On handoff, the new access
   router will register the same IPv6 HoA with the home agent each time
   with a different IPv4 care-of-address.

2.  Terminology

   The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD",  "SHOULD  NOT",  "RECOMMENDED",  "MAY",  and "OPTIONAL" in
   this document are to be interpreted as described in [RFC2119].

   The term NetMIPv4 used in this document refers to a Mobile IPv4
   client that is implemented in a network node.  This entity can
   perform Mobile IPv4 registration on behalf of the Mobile Node.

3.  Solution Overview

3.1  IPv6 addressing via IPv6CP

   For networks that use PPP as the link layer between the mobile Node
   (MN) and the Access Router (AR), the interface ID (IID) negotiation
   is performed via IPv6CP [RFC2023].

   Following successful IPv6CP negotiation and establishment of the
   unique link-local address, the AR initiates Router Advertisement (RA)
   messages using its link-local address as the source address, as per
   [RFC2461].  The RA messages contain a prefix used by the MS to
   configure global IPv6 addresses.  The AR supports Interface
   Identifier option negotiation.  The AR generates local Interface
   Identifier (for the local side of the PPP link) and Remote Interface
   Identifier (for the Mobile side of the PPP link).  The remote



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   Interface Identifier is assigned to the Mobile Node during IPv6CP
   negotiation.  The AR makes sure that the Interface Identifier is
   unique over the PPP link.  The Interface Identifier is used along
   with the IPv6 HL prefix to construct the 128-bit IPv6 address for the
   Mobile Node.

   The ARs conformant to this specification shall behaves as follows:

   Upon receiving an IPv6CP configure request with IID set to 0, the AR
   shall initiate a MIPv4 registration request to the home agent using a
   IPv4 FA-COA and request an IPv6 HoA or HL prefix from the home agent.
   The HA shall assign unique IPv6 HoA or HL prefix to a mobile node
   after successfully processing the registering request.  The HoA or HL
   prefix range may be configured as IPv6 pool with in HA.

   After receiving the MIPv4 RRP from the home agent with a valid IPv6
   HoA or HL prefix, the AR sends a Router Advertisement message which
   contains the HL prefix received from the home agent.  This is done
   assuming that at this time the IPv6CP negotiation with the MN is over
   and the PPP link has reached the NCP	open state.

   The AR and the home agent establish an IPv6-in-IPv4 tunnel using the
   FA-COA IPv4 address, the home agent's IPv4 address and the IPv6 HoA
   tuple.  The IPv6 traffic from the mobile node is carried in this
   IPv6-in-IPv4 tunnel to the home agent.  The 6to4 tunneling or other
   form of tunneling may be used to forward IPv6 data packets from the
   mobile node to another IPv6 Router/Host over the intermediate IPv4
   networks.

3.1.1  IPv6 Addressing with unique HL prefix

   In this section we show a scenario where an IPv6 address is assigned
   to the MN using an unique HL prefix:


















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   +----+        +-------+      +-------+   +-----+
   |    |        |       |      |       |   |     |
   | MN/|        |NAS/   |      | Home  |   |6to4 |
   |User|        |NetMIP4|      | Agent |   |Relay|
   |    |        |Client/|      |       |   |     |
   |    |        | FA    |      |       |   |     |
   +----+        +-------+      +-------+   +-----+
     |               |             |          |
     |     1         |             |          |
     |<------------->|             |          |
     |               |             |          |
     |     2         |             |          |
     |-------------->|             |          |
     |               |       3     |          |
     |     4         |------------>|          |
     |<--------------|             |          |
     |               |       5     |          |
     |               |<------------|          |
     |     6         |             |          |
     |<--------------|             |          |
     |               |             |          |
     |     7         |             |          |
     |-------------->|             |          |
     |               |             |          |
     |     8         |             |          |
     |-------------->|             |          |
     |               |             |          |
     |     9         |             |          |
     |<--------------|             |          |
     |               |             |          |
     |     10        |             |          |
     |-------------->|             |          |
     |               |             |          |
     |     11        |             |          |
     |<--------------|             |          |
     |               |             |          |
     |               |             |          |
   Auto Config 12    |             |          |
   IPv6 address      |             |          |
     |               |             |          |
     |     13        |             |          |
     |<------------->|<===========>|<========>|
     |               |             |          |




   Figure 1.  IPv6 Addressing with unique HL prefix



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   Description of the steps:

   1.  MN and the NAS performs LCP phase.  During this phase, the MN may
   run CHAP or PAP.  The NAS may authenticate the MN via an AAA
   infrastructure (not shown here).  At this step the AR (NAS) may
   receive a home agent address that should be used as the home agent to
   acquire an HoA/HL prefix for the MN.

   2.  The MN sends an IPv6CP config request with IID set to any number.

   3.  The AR (NetMIP4 Client) assigns an IID for the MN.  It sends a
   MIP4 RRQ to the home agent (either configured in the AR or received
   from the AAA server at step 1).  The RRQ includes the assigned IID
   for the MN in a HoA request extension.  The RRQ has the CoA field set
   to the FA-CoA of the AR.

   4.  The AR/NAS sends an IPv6CP config request to configure the IID
   that it wants to use for the IPv6 Link Local address.

   5.  The home agent registers the MN's session and assigns an HoA.
   The home agent constructs the HoA based on the received IID (lower 64
   bits) with an unique prefix (upper 64-bits).  The home agent may
   perform proxy DAD on the newly formed HoA.  Assuming proxy DAD
   produces no response, the home agent returns the HoA in the RRP.

   6.  The AR/NAS responds back to the MN with an IPv6CP config-NAK to
   suggest the IID that it wants the MN to use for link local address.
   This happens in response to step 2.

   7.  The MN sends back an IPv6CP config-ACK to acknowledge the IID
   that the AR/NAS proposed in step 4 that it would use.

   8.  The MN sends an IPv6CP config request to the AR/NAS with the IID
   that was assigned by the AR/NAS in step 6.

   9.  The AR/NAS sends back an IPv6CP config-ACK to the MN in response
   to step 8.

   10.  At this stage the MN and the AR/NAS PPP state machine should be
   in NCP open state.  The MN sends an Router Solicitation to the AR.

   11.  The AR responds with an Router Advertisement that contains a
   prefix set to the home link prefix of the HoA that was received at
   step 5.

   12.  The MN autoconfigures the IPv6 address with the IID and the
   prefix from step 9 and step 11.




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   13.  The MN's IPv6 traffic is tunneled by the AR to the HA via an
   v6overv4 tunnel and the HA tunnels the packets via another tunnel
   (6to4 in this illustration) to the v6 node/domain.

3.1.2  IPv6 Addressing with shared HL prefix

   In this section we show a scenario where an IPv6 address is assigned
   to the MN using a shared HL prefix:











































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   +----+        +-------+      +-------+   +-----+
   |    |        |       |      |       |   |     |
   | MN/|        |NAS/   |      | Home  |   |6to4 |
   |User|        |NetMIP4|      | Agent |   |Relay|
   |    |        |Client/|      |       |   |     |
   |    |        | FA    |      |       |   |     |
   +----+        +-------+      +-------+   +-----+
     |               |             |          |
     |     1         |             |          |
     |<------------->|             |          |
     |               |             |          |
     |     2         |             |          |
     |-------------->|             |          |
     |               |       3     |          |
     |     4         |------------>|          |
     |<--------------|             |          |
     |               |       5     |          |
     |               |<------------|          |
     |     6         |             |          |
     |<--------------|             |          |
     |               |             |          |
     |     7         |             |          |
     |-------------->|             |          |
     |               |             |          |
     |     8         |             |          |
     |-------------->|             |          |
     |               |             |          |
     |     9         |             |          |
     |<--------------|             |          |
     |               |             |          |
     |     10        |             |          |
     |-------------->|             |          |
     |               |             |          |
     |     11        |             |          |
     |<--------------|             |          |
     |               |             |          |
     |               |             |          |
   Auto Config 12    |             |          |
   IPv6 address      |             |          |
     |               |             |          |
     |     13        |             |          |
     |<------------->|<===========>|<========>|
     |               |             |          |




   Figure 1.  IPv6 Addressing with shared HL prefix



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   Description of the steps:

   1.  MN and the NAS performs LCP phase.  During this phase, the MN may
   run CHAP or PAP.  The NAS may authenticate the MN via an AAA
   infrastructure (not shown here).  At this step the AR (NAS) may
   receive a home agent address that should be used as the home agent to
   acquire an HoA/HL prefix for the MN.

   2.  The MN sends an IPv6CP config request with IID set to any number.

   3. in this case, the AR (NetMIP4 Client) does not assigns an IID for
   the MN.  It sends a MIP4 RRQ to the home agent (either configured in
   the AR or received from the AAA server	at step 1).  The RRQ includes
   IID=0 in a HoA request extension.  The RRQ has the CoA field set to
   the FA-CoA of the AR.

   4.  The AR/NAS sends an IPv6CP config request to configure the IID
   that it wants to use for the IPv6 Link Local address.

   5.  The home agent registers the MN's session and assigns an HoA.
   The home agent assigns an HoA for the MN from its pool.  Since the
   home agent is the custodian of the HoA (128-bits) it can use a HL
   prefix that is shared among number of registered MNs, there may not
   be a need to run proxy DAD for the assigned HoA in this case.  The
   home agent returns the HoA in the RRP.

   6.  The AR/NAS extracts the IID and the HL prefix from the received
   IPv6 HoA extension in the RRP (step 5).  The AR/NAS responds back to
   the MN with an IPv6CP config-NAK to suggest this IID.  This
   happens	in response to step 2.

   7.  The MN sends back an IPv6CP config-ACK to acknowledge the IID
   that the AR/NAS proposed in step 4 that it would use.

   8.  The MN sends an IPv6CP config request to the AR/NAS with the IID
   that was assigned by the AR/NAS in step 6.

   9.  The AR/NAS sends back an IPv6CP config-ACK to the MN in response
   to step 8.

   10.  At this stage the MN and the AR/NAS PPP state machine should be
   in NCP open state.  The MN sends an Router Solicitation to the AR.

   11.  The AR responds with an Router Advertisement that contains a
   prefix set to the home link prefix of the HoA (extracted at step 6)
   that was received at step 5.

   12.  The MN autoconfigures the IPv6 address with the IID and the



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   prefix from step 9 and step 11.

   13.  The MN's IPv6 traffic is tunneled by the AR to the HA via an
   v6overv4 tunnel and the HA tunnels the packets via another tunnel
   (6to4 in this illustration) to the v6 node/domain.

3.2  IPv6 addressing via DHCPv6

   For networks that use DHCPv6 for IPv6 address configuration, the MN
   and the AR exchanges DHCPv6 messages for this purpose.  In this
   section we describe the method via which the AR/NetMIPv4 Client
   acquires an HoA for the MN.

   It is assumed in this solution that the AR/NAS/FA, NetMIPv4 Client
   and the DHCP server (sort of a DHCP proxy) are collocated.

   The ARs conformant to this specification shall behaves as follows:

   Upon receiving an DHCP REQUEST from the MN (DHCP Client), the AR
   shall initiate a MIPv4 registration request to the home agent using a
   IPv4 FA-COA and request an IPv6 HoA or HL prefix from the home agent.
   The HA shall assign unique IPv6 HoA or HL prefix to a mobile node
   after successfully processing the registering request.  The HoA or HL
   prefix range may be configured as IPv6 pool with in HA.

   After receiving the MIPv4 RRP from the home agent with a valid IPv6
   HoA or HL prefix, the AR sends a DHCP REPLY message which contains
   the HoA received from the home agent.

   The AR and the home agent establish an IPv6-in-IPv4 tunnel using the
   FA-COA IPv4 address, the home agent's IPv4 address and the IPv6 HoA
   tuple.  The IPv6 traffic from the mobile node is carried in this
   IPv6-in-IPv4 tunnel to the home agent.  The 6to4 tunneling or other
   form of tunneling may be used to forward IPv6 data packets from the
   mobile node to another IPv6 Router/Host over the intermediate IPv4
   networks.

   The following call flow illustrates the IPv6 addressing with DHCPv6:













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   +----+        +-------+      +-------+   +-----+
   |    |        |       |      |       |   |     |
   | MN/|        |NAS/   |      | Home  |   |6to4 |
   |User|        |NetMIP4|      | Agent |   |Relay|
   |    |        |Client/|      |       |   |     |
   |    |        | FA/   |      |       |   |     |
   |    |        |DHCP-  |      |       |   |     |
   |    |        | proxy |      |       |   |     |
   +----+        +-------+      +-------+   +-----+
     |               |             |          |
     |     1         |             |          |
     |<------------->|             |          |
     |               |             |          |
     |     2         |             |          |
     |-------------->|             |          |
     |               |       3     |          |
     |               |------------>|          |
     |               |             |          |
     |               |       4     |          |
     |               |<------------|          |
     |     5         |             |          |
     |<--------------|             |          |
     |               |             |          |
     |               |             |          |
     |     6         |             |          |
     |<------------->|<===========>|<========>|
     |               |             |          |




   Figure 1.  Message flow for DHCPv6 based IPv6 addressing w/ NetMIP4

   Description of the steps:

   1.  MN and the NAS performs access authentication and authorization
   e.g.  EAP.  The NAS acting as the EAP authenticator authenticates the
   MN via an AAA infrastructure (not shown here).  At this step the AR
   (NAS) may receive a home agent address that should be used as the
   home agent to acquire an HoA prefix for the MN.

   2.  The MN sends an DHCP REQUEST message to the AR/DHCP-proxy.  It is
   assumed that the MN has discovered the DHCP-proxy address either via
   a SOLICIT message or an ADVERTISE message from the DHCP-proxy.  These
   messages are not shown in this call flow.

   3.  The AR (NetMIP4 Client) sends a MIP4 RRQ to the home agent
   (either configured in the AR or received from the AAA server at step



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   1).  The RRQ includes IID=0 in a HoA request extension.

   4.  The home agent registers the MN's session and assigns an HoA.
   The home agent assigns an HoA for the MN from its pool.  Since the
   home agent is the custodian of the HoA (128-bits) it can use a HL
   prefix that is shared among number of registered MNs, there may not
   be a need to run proxy DAD for the assigned HoA in this case.  The
   home agent returns the HoA in the RRP.

   5.  The AR/NAS responds back to the MN with an DHCP REPLY message
   containing the assigned HoA to the MN.

   6.  The MN's IPv6 traffic is tunneled by the AR to the HA via an
   v6overv4 tunnel and the HA tunnels the packets via another tunnel
   (6to4 in this illustration) to the v6 node/domain.

4.  MIPv4 Message Enhancements

   The following extensions are defined to exchange the Interface-ID and
   IPv6 HoA information between the AR and HA.  Note that any known and
   previously authenticated username(e.g the username that was
   authenticated during EAP or LCP)  can be used as the NAI for the
   MIPv4 session and sent in the MN-NAI extension.  If PPP/EAP username
   is not available, then another identifier will be needed to identify
   the session.  In some wireless networks It is possible to use the
   MSID of a subscriber or the hardware ID (e.g.  MAC address) of the MN
   to identify the session, carried in the MN-NAI extension.

4.1  IPv6 Home Address Request Extension

   The IPv6 Home Address Request Extension conforms to the Short
   Extension format specified for Mobile IPv4 [RFC3344].  The IPv6 Home
   Address Request Extension is not a skippable extension.  The format
   of the extension is as follows:


    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |     Type      |   Length      |    Sub-Type   |    IID ....
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type

      A 8-bit field indicating the type of the extension.  To be
      assigned by IANA.




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   Length

      A 8-bit field indicating the length of the option.  Set to 11.

   Sub-Type

      A 8-bit field not used in this extension.  It is set to 0.

   IID

      A 64-bit field set to the Interface ID allocated by the AR for the
      MN.

   Note that the IPv6 Home Address Request Extension is included by the
   AR only in the initial RRQ messages sent to HA.

   When the AR has locally assigned an Interface-ID to the MN, it
   includes the non-zero Interface-ID (64-bits) in this extension to
   request HA to assign a unique Home Link Prefix.  If the AR expects
   the HA to assign a Home Address (including Interface-ID), then the AR
   sets the Interface-ID in this extension to zero.

4.2  IPv6 Home Address Extension

   The IPv6 Home Address Extension may be included in the RRQ from the
   AR or in the RRP from the HA to identify a MIP registration.  Note
   that this may also be included in MIPv4 Revocation and Acknowledgment
   messages [RFC3543] for the same purpose.  The format of the extension
   is as follows:


    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |     Type      |   Length      |U| Reserved    |    IPv6 HoA ....
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type

      A 8-bit field indicating the type of the extension.  To be
      assigned by IANA.

   Length

      A 8-bit field indicating the length of the option.  Set to 19.





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   U

      When set this indicates the uniqueness of the HL prefix used to
      construct the HoA.

   Reserved

      Set to 0s.

   IPv6 HoA

      A 128-bit field set to the IPv6 address (HoA) allocated by the HA
      for the MN.

4.3  MIPv4 Registration Request and Reply

   For any MN that was assigned an IPv6 Home Address via NetMIPv4, the
   MIPv4 Registration Request from the AR may include one of the
   following extensions depending upon the type of request.

   The IPv6 Home Address Request Extension is included in initial
   registration request from the AR to the HA for session setup.

   The IPv6 Home Address Extension is included in renewal and de-
   registration requests from the AR to the HA.  It is also included in
   all Registration Reply messages from the HA.

   The IPv6 Home Address Request Extension and the IPv6 Home Address
   Extension must be included before the FA-HA Authentication Extension.

4.4  MIPv4 Registration Revocation Procedures

   For any MN that was assigned an IPv6 Home Address via NetMIPv4, the
   MIPv4 Registration Revocation and Revocation Acknowledgment messages
   [RFC3543] from the AR or the HA should include the IPv6 Home Address
   Extension to identify the MIP registration correctly.

   The IPv6 Home Address Extension must be included before the FA-HA
   Authentication Extension.  Note that the AR sends a deregistration
   Request (lifetime = 0) to terminate a binding at the HA and not a
   Revocation message and the HA responds with a Deregistration Reply.
   The HA sends a Revocation message to terminate a binding at the AR
   and the AR responds with an Acknowledgment message.

5.  Node Requirements

   This section describes the requirements for each of the nodes
   involved in this method.



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5.1  Mobile Node Requirements

   Mobile node behavior shall conform to the IPv6 specification defined
   in [RFC2472], [RFC2460], [RFC2461], [RFC2462], [RFC3315].  The
   Interface-Identifier is assigned by the AR to the Mobile during
   IPv6CP negotiation in case the MN uses IPv6 over PPP.  The HL prefix
   is assigned to the mobile in the Router Advertisement message.

5.2  Access Router/NAS/NetMIP4 Client/DHCP-proxy Requirements

5.2.1  IPv6 Addressing

   If the MN needs to be assigned a unique HL Prefix, the AR assigns an
   Interface-ID locally, and initiates NetMIP4 procedures to the HA.
   The AR sends a RRQ to HA including the IPv6 Home Address Request
   Extension with the Interface-ID set to the assigned Interface-ID.

   If the MN does not need a unique HL prefix, the AR initiates NetMIP4
   procedures to the HA when IPv6CP Conf-Req is received from the MN.
   The AR sends a RRQ to HA including the IPv6 Home Address Request
   Extension with the Interface-ID set to zero.

   When a RRP (Accepted) with IPv6 Home Address Extension is received
   with a valid home address, the AR extracts the HL prefix from the
   HoA.  The AR indicates the HL Prefix to the MN via a Router
   Advertisement message and puts the MN in connected state.

5.2.2  Authentication at the AR

   The PPP CHAP or PAP or EAP authentication shall be performed for IPv6
   network access.  For NetMIP4 procedures, the MN-HA, MN-FA, FA-HA
   authentication keys can be made available at the NetMIP4 Client via a
   key distribution scheme that is implemented at the AR.  All RRQ/RRP
   messages must be protected by the FA-HA Authentication Extension.
   The key distribution method is outside the scope of this document.

5.2.3  IPv6 Data processing

   When the AR receives an IPv6 PDU from the MN, the AR encapsulates the
   packet in a IPv4 packet and forwards it to the HA.  If the AR
   receives an IPv4 encapsulated IPv6 PDU from the HA, it removes the
   outer IPv4 header and forwards the IPv6 PDU to the MN.

5.3  Home Agent Requirements

5.3.1  IPv6 Addressing

   The HA needs to be configured with either IPv6 prefix pools or IPv6



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   address pools.  If Interface-ID is assigned at the AR, the HA cannot
   assign shared HL prefix; it has to be a unique HL prefix per MN.

   When a RRQ is received with IPv6 Home Address Request Extension that
   has a non-zero Interface-ID in it, the HA assigns a HL prefix to the
   MN, forms the global IPv6 address for the MN using the received
   Interface-ID and sends a Reply with IPv6 Home Address Extension.

   When a RRQ is received with IPv6 Home Address Request Extension with
   Interface-ID set to zero, the HA assigns a IPv6 Home address to the
   MN, and sends a Reply with IPv6 Home Address Extension.

   If the Interface-ID is assigned at the HA, the HA can choose to
   assign a shared or unique HL prefix per MN.  Optionally the HA can
   assign a unique HL prefix to the MN also.  The HA sets the Unique HL
   prefix bit "U" in the Home Address Extension to indicate this.

5.3.2  Authentication at the HA

   For NetMIP4 procedures, the MN-HA, FA-HA authentication keys can be
   made available at the Home Agent via a key distribution scheme that
   is implemented at the HA.  All RRQ/RRP messages must be protected by
   the FA-HA Authentication Extension.  The key distribution method is
   outside the scope of this document.

5.3.3  IPv6 Data processing

   When the HA receives a IPv6 PDU over a 6to4 tunnel from the default
   6to4router, it removes the IPv4 header and looks at the inner IPv6
   address.  If an tunnel has been established for this MN and there is
   a binding cache entry for the same, the HA encapsulates the packet in
   an IPv4 packet and forwards it to the AR.  If the HA receives an IPv4
   encapsulated IPv6 PDU from the AR, it removes the outer IPv4 header
   and forwards the IPv6 PDU over the 6to4 tunnel to the default 6to4
   router.

6.  Security Considerations

   The proposed method of acquiring IPv6 address via network based
   Mobile IPv4 (NetMIP4) requires secure key generation and key
   distribution for securing the RRQs and RRPs.  Although this key
   generation and distribution details are not part of this document, it
   is necessary to put in place a solution for this to prevent rouge
   network nodes to launch attacks on user's sessions.

   There are several work going on in IETF which are based on EAP keying
   framework.  Also several SDOs are developing key distribution schemes
   that can be leveraged for a solution.



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7.  IANA Considerations

   The following Extension Types MUST be assigned by IANA:

   IPv6 Home Address Request Extension Type: TBD-1.

   IPv6 Home Address Extension Type: TBD-2.

8.  Acknowledgements

   TBD.

9.  Normative References

   [RFC2023]  Haskin, D. and E. Allen, "IP Version 6 over PPP",
              RFC 2023, October 1996.

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

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

   [RFC2461]  Narten, T., Nordmark, E., and W. Simpson, "Neighbor
              Discovery for IP Version 6 (IPv6)", RFC 2461,
              December 1998.

   [RFC2462]  Thomson, S. and T. Narten, "IPv6 Stateless Address
              Autoconfiguration", RFC 2462, December 1998.

   [RFC2472]  Haskin, D. and E. Allen, "IP Version 6 over PPP",
              RFC 2472, December 1998.

   [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.

   [RFC3344]  Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
              August 2002.

   [RFC3543]  Glass, S. and M. Chandra, "Registration Revocation in
              Mobile IPv4", RFC 3543, August 2003.









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Authors' Addresses

   Jay Navali
   Starent Networks
   30 International Place
   Tewksbury, MA  01876
   US

   Phone: +1 978-851-1141
   Email: jnavali@starentnetworks.com


   Kuntal Chowdhury
   Starent Networks
   30 International Place
   Tewksbury, MA  01876
   US

   Phone: +1 214-550-1416
   Email: kchowdhury@starentnetworks.com































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