[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits] [IPR]

Versions: (draft-sgundave-mip6-proxymip6) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 RFC 5213

NETLMM WG                                         S. Gundavelli (Editor)
Internet-Draft                                                  K. Leung
Intended status: Standards Track                                   Cisco
Expires: August 12, 2008                                  V. Devarapalli
                                                         Azaire Networks
                                                            K. Chowdhury
                                                        Starent Networks
                                                                B. Patil
                                                  Nokia Siemens Networks
                                                       February 09, 2008


                           Proxy Mobile IPv6
                   draft-ietf-netlmm-proxymip6-10.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
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   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."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on August 12, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2008).

Abstract

   Network-based mobility management enables IP mobility for a host
   without requiring its participation in any mobility related



Gundavelli (Editor), et al.  Expires August 12, 2008            [Page 1]

Internet-Draft              Proxy Mobile IPv6              February 2008


   signaling.  The Network is responsible for managing IP mobility on
   behalf of the host.  The mobility entities in the network are
   responsible for tracking the movements of the host and initiating the
   required mobility signaling on its behalf.  This specification
   describes a network-based mobility management protocol and is
   referred to as Proxy Mobile IPv6.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Conventions & Terminology  . . . . . . . . . . . . . . . . . .  4
     2.1.  Conventions used in this document  . . . . . . . . . . . .  5
     2.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Proxy Mobile IPv6 Protocol Overview  . . . . . . . . . . . . .  8
   4.  Proxy Mobile IPv6 Protocol Security  . . . . . . . . . . . . . 14
     4.1.  Peer Authorization Database Entries  . . . . . . . . . . . 15
     4.2.  Security Policy Database Entries . . . . . . . . . . . . . 15
   5.  Local Mobility Anchor Operation  . . . . . . . . . . . . . . . 16
     5.1.  Extensions to Binding Cache Entry Data Structure . . . . . 16
     5.2.  Supported Home Network Prefix Models . . . . . . . . . . . 18
     5.3.  Signaling Considerations . . . . . . . . . . . . . . . . . 18
       5.3.1.  Processing Binding Registrations . . . . . . . . . . . 18
       5.3.2.  Initial Binding Registration (New Mobility Session)  . 20
       5.3.3.  Binding Lifetime Extension (No handoff)  . . . . . . . 21
       5.3.4.  Binding Lifetime Extension (After handoff) . . . . . . 22
       5.3.5.  Binding De-Registration  . . . . . . . . . . . . . . . 22
       5.3.6.  Constructing the Proxy Binding Acknowledgement
               Message  . . . . . . . . . . . . . . . . . . . . . . . 23
     5.4.  Multihoming Support  . . . . . . . . . . . . . . . . . . . 25
       5.4.1.  Binding Cache entry lookup considerations  . . . . . . 26
     5.5.  Timestamp Option for Message Ordering  . . . . . . . . . . 31
     5.6.  Routing Considerations . . . . . . . . . . . . . . . . . . 34
       5.6.1.  Bi-Directional Tunnel Management . . . . . . . . . . . 34
       5.6.2.  Forwarding Considerations  . . . . . . . . . . . . . . 34
     5.7.  Local Mobility Anchor Address Discovery  . . . . . . . . . 35
     5.8.  Mobile Prefix Discovery Considerations . . . . . . . . . . 36
     5.9.  Route Optimizations Considerations . . . . . . . . . . . . 36
   6.  Mobile Access Gateway Operation  . . . . . . . . . . . . . . . 36
     6.1.  Extensions to Binding Update List Entry Data Structure . . 37
     6.2.  Mobile Node's Policy Profile . . . . . . . . . . . . . . . 38
     6.3.  Supported Access Link Types  . . . . . . . . . . . . . . . 38
     6.4.  Supported Address Configuration Modes  . . . . . . . . . . 39
     6.5.  Access Authentication & Mobile Node Identification . . . . 39
     6.6.  Acquiring Mobile Node's Identifier . . . . . . . . . . . . 40
     6.7.  Home Network Emulation . . . . . . . . . . . . . . . . . . 40
     6.8.  Link-Local and Global Address Uniqueness . . . . . . . . . 41
     6.9.  Signaling Considerations . . . . . . . . . . . . . . . . . 42



Gundavelli (Editor), et al.  Expires August 12, 2008            [Page 2]

Internet-Draft              Proxy Mobile IPv6              February 2008


       6.9.1.  Binding Registrations  . . . . . . . . . . . . . . . . 42
       6.9.2.  Router Solicitation Messages . . . . . . . . . . . . . 50
       6.9.3.  Default-Router Lifetime  . . . . . . . . . . . . . . . 50
       6.9.4.  Retransmissions and Rate Limiting  . . . . . . . . . . 51
     6.10. Routing Considerations . . . . . . . . . . . . . . . . . . 52
       6.10.1. Transport Network  . . . . . . . . . . . . . . . . . . 52
       6.10.2. Tunneling & Encapsulation Modes  . . . . . . . . . . . 53
       6.10.3. Local Routing  . . . . . . . . . . . . . . . . . . . . 53
       6.10.4. Tunnel Management  . . . . . . . . . . . . . . . . . . 54
       6.10.5. Forwarding Rules . . . . . . . . . . . . . . . . . . . 54
     6.11. Supporting DHCPv6 based Address Configuration on the
           Access Link  . . . . . . . . . . . . . . . . . . . . . . . 55
     6.12. Home Network Prefix Renumbering  . . . . . . . . . . . . . 56
     6.13. Mobile Node Detachment Detection and Resource Cleanup  . . 57
     6.14. Allowing network access to other IPv6 nodes  . . . . . . . 57
   7.  Mobile Node Operation  . . . . . . . . . . . . . . . . . . . . 58
     7.1.  Moving into a Proxy Mobile IPv6 Domain . . . . . . . . . . 58
     7.2.  Roaming in the Proxy Mobile IPv6 Domain  . . . . . . . . . 59
   8.  Message Formats  . . . . . . . . . . . . . . . . . . . . . . . 59
     8.1.  Proxy Binding Update Message . . . . . . . . . . . . . . . 60
     8.2.  Proxy Binding Acknowledgement Message  . . . . . . . . . . 61
     8.3.  Home Network Prefix Option . . . . . . . . . . . . . . . . 63
     8.4.  Handoff Indicator Option . . . . . . . . . . . . . . . . . 64
     8.5.  Access Technology Type Option  . . . . . . . . . . . . . . 65
     8.6.  Mobile Node Interface Identifier Option  . . . . . . . . . 67
     8.7.  Link-local Address Option  . . . . . . . . . . . . . . . . 68
     8.8.  Timestamp Option . . . . . . . . . . . . . . . . . . . . . 68
     8.9.  Status Values  . . . . . . . . . . . . . . . . . . . . . . 69
   9.  Protocol Configuration Variables . . . . . . . . . . . . . . . 71
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 72
   11. Security Considerations  . . . . . . . . . . . . . . . . . . . 73
   12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 74
   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 74
     13.1. Normative References . . . . . . . . . . . . . . . . . . . 74
     13.2. Informative References . . . . . . . . . . . . . . . . . . 75
   Appendix A.  Proxy Mobile IPv6 interactions with AAA
                Infrastructure  . . . . . . . . . . . . . . . . . . . 76
   Appendix B.  Supporting Shared-Prefix Model using DHCPv6 . . . . . 76
   Appendix C.  Routing State . . . . . . . . . . . . . . . . . . . . 77
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 78
   Intellectual Property and Copyright Statements . . . . . . . . . . 80










Gundavelli (Editor), et al.  Expires August 12, 2008            [Page 3]

Internet-Draft              Proxy Mobile IPv6              February 2008


1.  Introduction

   IP mobility for IPv6 hosts is specified in Mobile IPv6 [RFC-3775].
   Mobile IPv6 requires client functionality in the IPv6 stack of a
   mobile node.  Exchange of signaling messages between the mobile node
   and home agent enables the creation and maintenance of a binding
   between the mobile node's home address and its care-of-address.
   Mobility as specified in [RFC-3775] requires the IP host to send IP
   mobility management signaling messages to the home agent, which is
   located in the network.

   Network-based mobility is another approach to solving the IP mobility
   challenge.  It is possible to support mobility for IPv6 nodes without
   host involvement by extending Mobile IPv6 [RFC-3775] signaling
   messages between a network node and a home agent.  This approach to
   supporting mobility does not require the mobile node to be involved
   in the exchange of signaling messages between itself and the home
   agent.  A proxy mobility agent in the network performs the signaling
   with the home agent and does the mobility management on behalf of the
   mobile node attached to the network.  Because of the use and
   extension of Mobile IPv6 signaling and home agent functionality, this
   protocol is referred to as Proxy Mobile IPv6 (PMIPv6).

   Network deployments which are designed to support mobility would be
   agnostic to the capability in the IPv6 stack of the nodes which it
   serves.  IP mobility for nodes which have mobile IP client
   functionality in the IPv6 stack as well as those nodes which do not,
   would be supported by enabling Proxy Mobile IPv6 protocol
   functionality in the network.  The advantages of developing a network
   based mobility protocol based on Mobile IPv6 are:

   o  Reuse of home agent functionality and the messages/format used in
      mobility signaling.  Mobile IPv6 is a mature protocol with several
      implementations that have undergone interoperability testing.

   o  A common home agent would serve as the mobility agent for all
      types of IPv6 nodes.

   The problem statement and the need for a network based mobility
   protocol solution has been documented in [RFC-4830].  Proxy Mobile
   IPv6 is a solution that addresses these issues and requirements.


2.  Conventions & Terminology







Gundavelli (Editor), et al.  Expires August 12, 2008            [Page 4]

Internet-Draft              Proxy Mobile IPv6              February 2008


2.1.  Conventions used in this document

   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 [RFC-2119].


2.2.  Terminology

   All the general mobility related terms used in this document are to
   be interpreted as defined in the Mobile IPv6 base specification [RFC-
   3775].

   This document adopts the terms, Local Mobility Anchor (LMA) and
   Mobile Access Gateway (MAG) from the NETLMM Goals document [RFC-
   4831].  This document also provides the following context specific
   explanation to the following terms used in this document.


   Proxy Mobile IPv6 Domain (PMIPv6-Domain)

      Proxy Mobile IPv6 domain refers to the network where the mobility
      management of a mobile node is handled using the Proxy Mobile IPv6
      protocol as defined in this specification.  The Proxy Mobile IPv6
      domain includes local mobility anchors and mobile access gateways
      between which security associations can be setup and authorization
      for sending Proxy Binding Updates on behalf of the mobile nodes
      can be ensured.

   Local Mobility Anchor (LMA)

      Local Mobility Anchor is the home agent for the mobile node in the
      Proxy Mobile IPv6 domain.  It is the topological anchor point for
      the mobile node's home network prefix and is the entity that
      manages the mobile node's binding state.  The local mobility
      anchor has the functional capabilities of a home agent as defined
      in Mobile IPv6 base specification [RFC-3775] with the additional
      capabilities required for supporting Proxy Mobile IPv6 protocol as
      defined in this specification.

   Mobile Access Gateway (MAG)

      Mobile Access Gateway is a function that manages the mobility
      related signaling for a mobile node that is attached to its access
      link.  It is responsible for tracking the mobile node's movements
      to and from the access link and for signaling the mobile node's
      local mobility anchor.




Gundavelli (Editor), et al.  Expires August 12, 2008            [Page 5]

Internet-Draft              Proxy Mobile IPv6              February 2008


   Mobile Node (MN)

      Throughout this document, the term mobile node is used to refer to
      an IP host or router whose mobility is managed by the network.
      The mobile node may be operating in IPv6 mode, IPv4 mode or in
      IPv4/IPv6 dual mode.  The mobile node is not required to
      participate in any IP mobility related signaling for achieving
      mobility for an IP address that is obtained in that Proxy Mobile
      IPv6 domain.

   LMA Address (LMAA)

      The address that is configured on the interface of the local
      mobility anchor and is the transport endpoint of the bi-
      directional tunnel established between the local mobility anchor
      and the mobile access gateway.  This is the address to where the
      mobile access gateway sends the Proxy Binding Update messages.
      When supporting IPv4 traversal, i.e., when the network between the
      local mobility anchor and the mobile access gateway is an IPv4
      network, this address will be an IPv4 address and will be referred
      to as IPv4-LMAA, as specified in [ID-IPV4-PMIP6].

   Proxy Care-of Address (Proxy-CoA)

      Proxy-CoA is the address configured on the interface of the mobile
      access gateway and is the transport endpoint of the tunnel between
      the local mobility anchor and the mobile access gateway.  The
      local mobility anchor views this address as the Care-of Address of
      the mobile node and registers it in the Binding Cache entry for
      that mobile node.  When the transport network between the mobile
      access gateway and the local mobility anchor is an IPv4 network
      and if the care-of address that is registered at the local
      mobility anchor is an IPv4 address, the term, IPv4-Proxy-CoA is
      used, as specified in [ID-IPV4-PMIP6].

   Mobile Node's Home Address (MN-HoA)

      MN-HoA is an address from a mobile node's home network prefix in a
      Proxy Mobile IPv6 domain.  The mobile node will be able to use
      this address as long as it is attached to the access network that
      is in the scope of that Proxy Mobile IPv6 domain.  Unlike in
      Mobile IPv6 where the home agent is aware of the home address of
      the mobile node, in Proxy Mobile IPv6, the mobility entities are
      only aware of the mobile node's home network prefix and are not
      always aware of the exact address(es) that the mobile node
      configured on its interface from that prefix.

   Mobile Node's Home Network Prefix (MN-HNP)



Gundavelli (Editor), et al.  Expires August 12, 2008            [Page 6]

Internet-Draft              Proxy Mobile IPv6              February 2008


      This is the on-link IPv6 prefix that is always present in the
      Router Advertisements that the mobile node receives when it is
      attached to any of the access links in that Proxy Mobile IPv6
      domain.  This home network prefix is topologically anchored at the
      mobile node's local mobility anchor.  The mobile node configures
      its interface with an address from this prefix.  If the mobile
      node connects to the Proxy Mobile IPv6 domain through multiple
      interfaces, simultaneously, each of the connected interface will
      be assigned a unique home network prefix and under a different
      mobility session.

   Mobile Node's Home Link

      This is the link on which the mobile node obtained its Layer-3
      address configuration for the attached interface after it moved
      into that Proxy Mobile IPv6 domain.  This is the link that
      conceptually follows the mobile node.  The network will ensure the
      mobile node always sees this link with respect to the layer-3
      network configuration, on any access link that it attaches to in
      that Proxy Mobile IPv6 domain.

   Multihomed Mobile Node

      A mobile node that connects to the Proxy Mobile IPv6 domain
      through more than one interface and uses these interfaces
      simultaneously is referred to as a multihomed mobile node.

   Mobile Node Identifier (MN-Identifier)

      The identity of a mobile node in the Proxy Mobile IPv6 domain.
      This is the stable identifier of a mobile node that the mobility
      entities in a Proxy Mobile IPv6 domain can always acquire and use
      it for predictably identifying a mobile node.  This is typically
      an identifier such as NAI or other identifier such as a MAC
      address.

   Mobile Node Interface Identifier (MN-Interface-Identifier)

      The interface identifier that identifies a given interface of a
      mobile node.  For those interfaces that have a layer-2 identifier,
      the interface identifier can be based on that layer-2 identifier.
      The interface identifier in some cases is generated by the mobile
      node and conveyed to the access router or the mobile access
      gateway.  In some cases, there might not be any interface
      identifier associated with the mobile node's interface.

   Policy Profile




Gundavelli (Editor), et al.  Expires August 12, 2008            [Page 7]

Internet-Draft              Proxy Mobile IPv6              February 2008


      Policy Profile is an abstract term for referring to a set of
      configuration parameters that are configured for a given mobile
      node.  The mobility entities in the Proxy Mobile IPv6 domain
      require access to these parameters for providing the mobility
      management to a given mobile node.  The specific details on how
      the network entities obtain this policy profile is outside the
      scope of this document.

   Proxy Binding Update (PBU)

      A binding registration request message sent by a mobile access
      gateway to a mobile node's local mobility anchor for establishing
      a binding between the mobile node's MN-HNP and the Proxy-CoA.

   Proxy Binding Acknowledgement (PBA)

      A binding registration reply message sent by a local mobility
      anchor in response to a Proxy Binding Update request message that
      it received from a mobile access gateway.


3.  Proxy Mobile IPv6 Protocol Overview

   This specification describes a network-based mobility management
   protocol.  It is called Proxy Mobile IPv6 and is based on Mobile IPv6
   [RFC-3775].

   Proxy Mobile IPv6 protocol is intended for providing network-based IP
   mobility management support to a mobile node, without requiring the
   participation of the mobile node in any IP mobility related
   signaling.  The mobility entities in the network will track the
   mobile node's movements and will initiate the mobility signaling and
   setup the required routing state.

   The core functional entities in the NETLMM infrastructure are the
   Local Mobility Anchor (LMA) and the Mobile Access Gateway (MAG).  The
   local mobility anchor is responsible for maintaining the mobile
   node's reachability state and is the topological anchor point for the
   mobile node's home network prefix.  The mobile access gateway is the
   entity that performs the mobility management on behalf of a mobile
   node and it resides on the access link where the mobile node is
   anchored.  The mobile access gateway is responsible for detecting the
   mobile node's movements to and from the access link and for
   initiating binding registrations to the mobile node's local mobility
   anchor.  The architecture of a Proxy Mobile IPv6 domain is shown in
   Figure 1.





Gundavelli (Editor), et al.  Expires August 12, 2008            [Page 8]

Internet-Draft              Proxy Mobile IPv6              February 2008


               +----+                +----+
               |LMA1|                |LMA2|
               +----+                +----+
        LMAA1 -> |                      | <-- LMAA2
                 |                      |
                 \\                    //\\
                  \\                  //  \\
                   \\                //    \\
                +---\\------------- //------\\----+
               (     \\  IPv4/IPv6 //        \\    )
               (      \\  Network //          \\   )
                +------\\--------//------------\\-+
                        \\      //              \\
                         \\    //                \\
                          \\  //                  \\
              Proxy-CoA1--> |                      | <-- Proxy-CoA2
                         +----+                 +----+
                         |MAG1|-----{MN2}       |MAG2|
                         +----+    |            +----+
                           |       |               |
              MN-HoA1 -->  |     MN-HoA2           | <-- MN-HoA3
                         {MN1}                   {MN3}




                    Figure 1: Proxy Mobile IPv6 Domain



   Once a mobile node enters a Proxy Mobile IPv6 domain and attaches to
   an access link, the mobile access gateway on that access link, after
   identifying the mobile node and acquiring its identity, will
   determine if the mobile node is authorized for the network-based
   mobility management service.

   If the network determines that the network-based mobility management
   service needs to be offered to that mobile node, the network will
   ensure that the mobile node using any of the address configuration
   mechanisms permitted by the network will be able to obtain the
   address configuration on the connected interface and move anywhere in
   that Proxy Mobile IPv6 domain.  The obtained address configuration
   includes the address(es) from its home network prefix, the default-
   router address on the link and other related configuration
   parameters.  From the perspective of the mobile node, the entire
   Proxy Mobile IPv6 domain appears as a single link, the network
   ensures that the mobile node believes it is always on the same link
   where it obtained its initial address configuration, even after



Gundavelli (Editor), et al.  Expires August 12, 2008            [Page 9]

Internet-Draft              Proxy Mobile IPv6              February 2008


   changing its point of attachment in that network.

   The mobile node may be operating in an IPv4-only mode, IPv6-only mode
   or in dual IPv4/IPv6 mode.  Based on what is enabled in the network
   for that mobile node, the mobile node will be able to obtain an IPv4,
   IPv6 or dual IPv4/IPv6 addresses and move anywhere in that Proxy
   Mobile IPv6 domain.  However, the specific details related to the
   IPv4 addressing or IPv4 transport support are specified in the
   companion document [ID-IPV4-PMIP6].

   If the mobile node connects to the Proxy Mobile IPv6 domain, through
   multiple interfaces and over multiple access networks, the network
   will allocate a unique home network prefix for each of the connected
   interfaces and the mobile node will be able to configure an
   address(es) on those interfaces from the respective home network
   prefixes.  However, if the mobile node performs an handoff from one
   interface to another and if the local mobility anchor receives an
   handoff hint from the serving mobile access gateway about the same,
   the local mobility anchor will assign the same prefix to the new
   interface.































Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 10]

Internet-Draft              Proxy Mobile IPv6              February 2008


    +-----+                +-----+                +-----+
    | MN  |                | MAG |                | LMA |
    +-----+                +-----+                +-----+
       |                      |                      |
   MN Attached                |                      |
       |                      |                      |
       |               MN Attached Event             |
       |        (Acquire MN-Id and Profile)          |
       |                      |                      |
       |                      |----- PBU ----------->|
       |                      |                      |
       |                      |                  Accept PBU
       |                      |  (Allocate MN-HNP, Setup BCE and Tunnel)
       |                      |                      |
       |                      |<--------- PBA -------|
       |                      |                      |
       |                 Accept PBA                  |
       |          (Setup Tunnel and Routing)         |
       |                      |                      |
       |                      |==== Bi-Dir Tunnel ===|
       |                      |                      |
       |--- Rtr Sol --------->|                      |
       |                      |                      |
       |<------- Rtr Adv -----|                      |
       |                      |                      |
    IP Address                |                      |
   Configuration              |                      |
       |                      |                      |




          Figure 2: Mobile Node Attachment - Signaling Call Flow



   Figure 2 shows the signaling call flow when the mobile node enters
   the Proxy Mobile IPv6 domain.


   For updating the local mobility anchor about the current location of
   the mobile node, the mobile access gateway sends a Proxy Binding
   Update message to the mobile node's local mobility anchor.  Upon
   accepting this Proxy Binding Update message, the local mobility
   anchor sends a Proxy Binding Acknowledgement message including the
   mobile node's home network prefix.  It also creates the Binding Cache
   entry and establishes a bi-directional tunnel to the mobile access
   gateway.



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 11]

Internet-Draft              Proxy Mobile IPv6              February 2008


   The mobile access gateway on receiving the Proxy Binding
   Acknowledgement message sets up a bi-directional tunnel to the local
   mobility anchor and sets up the data path for the mobile node's
   traffic.  At this point the mobile access gateway will have all the
   required information for emulating the mobile node's home link.  It
   sends Router Advertisement messages to the mobile node on the access
   link advertising the mobile node's home network prefix as the hosted
   on-link-prefix.

   The mobile node on receiving these Router Advertisement messages on
   the access link will attempt to configure its interface either using
   stateful or stateless address configuration modes, based on the modes
   that are permitted on that access link.  At the end of a successful
   address configuration procedure, the mobile node will end up with an
   address from its home network prefix.

   Once the address configuration is complete, the mobile node has a
   valid address from its home network prefix at the current point of
   attachment.  The serving mobile access gateway and the local mobility
   anchor also have proper routing states for handling the traffic sent
   to and from the mobile node using an address from its home network
   prefix.

   The local mobility anchor, being the topological anchor point for the
   mobile node's home network prefix, receives any packets that are sent
   by any correspondent node to the mobile node.  The local mobility
   anchor forwards these received packets to the mobile access gateway
   through the bi-directional tunnel.  The mobile access gateway on
   other end of the tunnel, after receiving the packet, removes the
   outer header and forwards the packet on the access link to the mobile
   node.

   The mobile access gateway typically acts as a default router on the
   access link.  Any packet that the mobile node sends to any
   correspondent node will be received by the mobile access gateway and
   will be sent to its local mobility anchor through the bi-directional
   tunnel.  The local mobility anchor on the other end of the tunnel,
   after receiving the packet, removes the outer header and routes the
   packet to the destination.












Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 12]

Internet-Draft              Proxy Mobile IPv6              February 2008


    +-----+          +-----+          +-----+          +-----+
    | MN  |          |p-MAG|          | LMA |          |n-MAG|
    +-----+          +-----+          +-----+          +-----+
       |                |                |                |
       |                |==Bi-Dir Tunnel=|                |
   MN Detached          |                |                |
       |         MN Detached Event       |                |
       |                |                |                |
       |                |-- DeReg PBU -->|                |
       |                |                |                |
       |                |            Accept PBU           |
       |                |   (Start MinDelayBeforeBCEDelete Timer)
       |                |                |                |
       |                |<-------- PBA --|                |
       |                |                |                |
   MN Attached          |                |                |
       |                |                |       MN Attached Event
       |                |                |   (Acquire MN-Id and Profile)
                               ....
                                    Registration steps as in fig 2.
                               ....
       |                |                |==Bi-Dir Tunnel=|
       |--- Rtr Sol ------------------------------------->|
       |                |                |                |
       |<------------------------------------ Rtr Adv ----|
       |                |                |                |
   MN retains HoA/HNP
       |                |                |                |


            Figure 3: Mobile Node Handoff - Signaling Call Flow



   Figure 3 shows the signaling call flow for the mobile node's handoff
   from previously attached mobile access gateway (p-MAG) to the newly
   attached mobile access gateway (n-MAG).  This call flow reflects only
   a specific message ordering, it is possible the registration message
   from the n-MAG may arrive before the de-registration message from the
   p-MAG arrives.


   After obtaining the initial address configuration in the Proxy Mobile
   IPv6 domain, if the mobile node changes its point of attachment, the
   mobile access gateway on the previous link will detect the mobile
   node's detachment from the link and will signal the local mobility
   anchor and will remove the binding and routing state for that mobile
   node.  However, the local mobility anchor upon accepting the request



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 13]

Internet-Draft              Proxy Mobile IPv6              February 2008


   will wait for certain amount of time before it deletes the binding,
   for allowing a smooth handoff.

   The mobile access gateway on the new access link upon detecting the
   mobile node on its access link will signal the local mobility anchor
   for updating the binding state.  Once that signaling is complete, the
   mobile node will continue to receive the Router Advertisements
   containing its home network prefix, making it believe it is still on
   the same link and it will use the same address configuration on the
   new access link.



4.  Proxy Mobile IPv6 Protocol Security

   The signaling messages, Proxy Binding Update and Proxy Binding
   Acknowledgement, exchanged between the mobile access gateway and the
   local mobility anchor MUST be protected using end-to-end security
   association(s) offering integrity and data origin authentication.

   The mobile access gateway and the local mobility anchor MUST
   implement IPsec for protecting the Proxy Mobile IPv6 signaling
   messages [RFC-4301].  That is, IPsec is mandatory to implement
   security mechanism.  However, additional documents may specify
   alternative mechanisms.

   IPsec ESP [RFC-4303] in transport mode with mandatory integrity
   protection SHOULD be used for protecting the signaling messages.
   Confidentiality protection of these messages is not required.

   IKEv2 [RFC-4306] SHOULD be used to setup security associations
   between the mobile access gateway and the local mobility anchor to
   protect the Proxy Binding Update and Proxy Binding Acknowledgement
   messages.  The mobile access gateway and the local mobility anchor
   can use any of the authentication mechanisms, as specified in IKEv2,
   for mutual authentication.

   The Mobile IPv6 specification [RFC-3775] requires the home agent to
   prevent a mobile node from creating security associations or creating
   binding cache entries for another mobile node's home address.  In the
   protocol described in this document, the mobile node is not involved
   in creating security associations for protecting the signaling
   messages or sending binding updates.  Therefore, the local mobility
   anchor MUST restrict the creation and manipulation of proxy bindings
   to specifically authorized mobile access gateways and prefixes.  The
   local mobility anchor MUST be locally configurable to authorize such
   specific combinations.  Additional mechanisms such as a policy store
   or AAA may be employed, but these are outside the scope of this



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 14]

Internet-Draft              Proxy Mobile IPv6              February 2008


   specification.

4.1.  Peer Authorization Database Entries

   This section describes PAD entries [RFC-4301] on the mobile access
   gateway and the local mobility anchor.  The PAD entries are only
   example configurations.  Note that the PAD is a logical concept and a
   particular mobile access gateway or a local mobility anchor
   implementation can implement the PAD in any implementation specific
   manner.  The PAD state may also be distributed across various
   databases in a specific implementation.


       mobile access gateway PAD:
         - IF remote_identity = lma_identity_1
              Then authenticate (shared secret/certificate/EAP)
              and authorize CHILD_SA for remote address lma_addres_1

       local mobility anchor PAD:
         - IF remote_identity = mag_identity_1
              Then authenticate (shared secret/certificate/EAP)
              and authorize CHILD_SAs for remote address mag_address_1


                           Figure 4: PAD Entries

   The list of authentication mechanisms in the above examples is not
   exhaustive.  There could be other credentials used for authentication
   stored in the PAD.

4.2.  Security Policy Database Entries

   This section describes the security policy entries [RFC-4301] on the
   mobile access gateway and the local mobility anchor required to
   protect the Proxy Mobile IPv6 signaling messages.  The SPD entries
   are only example configurations.  A particular mobile access gateway
   or a local mobility anchor implementation could configure different
   SPD entries as long as they provide the required security.

   In the examples shown below, the identity of the mobile access
   gateway is assumed to be mag_1, the address of the mobile access
   gateway is assumed to be mag_address_1, and the address of the local
   mobility anchor is assumed to be lma_address_1.








Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 15]

Internet-Draft              Proxy Mobile IPv6              February 2008


      mobile access gateway SPD-S:
        - IF local_address = mag_address_1 &
             remote_address = lma_address_1 &
             proto = MH & local_mh_type = BU & remote_mh_type = BA
          Then use SA ESP transport mode
          Initiate using IDi = mag_1 to address lma_address_1

      local mobility anchor SPD-S:
        - IF local_address = lma_address_1 &
             remote_address = mag_address_1 &
             proto = MH & local_mh_type = BA & remote_mh_type = BU
          Then use SA ESP transport mode


                           Figure 5: SPD Entries


5.  Local Mobility Anchor Operation

   The local mobility anchor MUST support the home agent function as
   defined in [RFC-3775] and additionally the extensions defined in this
   specification.  A home agent with these modifications and enhanced
   capabilities for supporting Proxy Mobile IPv6 protocol is referred to
   as the local mobility anchor.

   This section describes the operational details of the local mobility
   anchor.

5.1.  Extensions to Binding Cache Entry Data Structure

   Every local mobility anchor MUST maintain a Binding Cache entry for
   each currently registered mobile node.  Binding Cache entry is a
   conceptual data structure, described in Section 9.1 [RFC-3775].

   For supporting this specification, the Binding Cache Entry data
   structure needs to be extended with the following additional fields.


   o  A flag indicating whether or not this Binding Cache entry is
      created due to a proxy registration.  This flag is enabled for
      Binding Cache entries that are proxy registrations and is turned
      off for all other entries.

   o  The identifier of the registered mobile node, MN-Identifier.  This
      identifier is obtained from the Mobile Node Identifier Option
      [RFC-4283] present in the received Proxy Binding Update request.





Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 16]

Internet-Draft              Proxy Mobile IPv6              February 2008


   o  The interface identifier of the mobile node's connected interface
      on the access link.  This identifier can be acquired from the
      Mobile Node Interface Identifier option, present in the received
      Proxy Binding Update request.  If the option was not present in
      the request, the value MUST be set to ALL_ZERO.

   o  The Link-local address of the mobile node on the interface
      attached to the access link.  This is obtained from the Link-local
      Address option, present in the Proxy Binding Update request.  If
      the option was not present in the request, the value MUST be set
      to ALL_ZERO.

   o  The IPv6 home network prefix that is assigned to the mobile node's
      connected interface.  The home network prefix of the mobile node
      may have been statically configured in the mobile node's policy
      profile, or, it may have been dynamically allocated by the local
      mobility anchor.  The IPv6 home network prefix also includes the
      corresponding prefix length.

   o  The interface identifier (If-Id) of the bi-directional tunnel
      between the local mobility anchor and the mobile access gateway
      where the mobile node is currently anchored.  This is internal to
      the local mobility anchor.  The tunnel interface identifier is
      acquired during the tunnel creation.

   o  The access technology type, using which the mobile node is
      currently attached.  This is obtained from the Access Technology
      Type option, present in the Proxy Binding Update request.

   o  The 64-bit timestamp value of the most recently accepted Proxy
      Binding Update request sent for this mobile node.  This is the
      time-of-day on the local mobility anchor, when the message was
      received.  If the Timestamp option is not present in the Proxy
      Binding Update request (i.e., when sequence number based scheme is
      in use), the value MUST be set to ALL_ZERO.


   Typically, the mobile node's home network prefix is the key for
   locating a Binding Cache entry in all cases except when there has
   been an handoff of the mobile node's session to a new mobile access
   gateway and that mobile access gateway is unaware of the home network
   prefix that was assigned to the handed of session.  In such handoff
   cases, the Binding Cache entry can be located under the
   considerations specified in Section 5.4.1.







Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 17]

Internet-Draft              Proxy Mobile IPv6              February 2008


5.2.  Supported Home Network Prefix Models

   This specification supports Per-MN-Prefix model and does not support
   Shared-Prefix model.  As per the Per-MN-Prefix model, there will be a
   unique home network prefix assigned to each mobile node and no other
   node shares an address from that prefix.  The assigned prefix is
   unique to a mobile node and also unique to a given interface of the
   mobile node.  If the mobile node attaches to the Proxy Mobile IPv6
   domain through multiple interfaces and simultaneously, each of those
   connected interfaces will be assigned a different prefix.

   The mobile node's home network prefix is always hosted on the access
   link where the mobile node is anchored.  Conceptually, the entire
   home network prefix follows the mobile node as it moves within the
   Proxy Mobile IPv6 domain.  The local mobility anchor is not required
   to perform any proxy ND operations [RFC-4861] for defending the
   mobile node's home address on the home link.  However, from the
   routing perspective, the home network prefix is topologically
   anchored on the local mobility anchor.

5.3.  Signaling Considerations


   This section provides the rules for processing the signaling
   messages.  The processing rules specified in this section and other
   related sections are chained and are in a specific order.  When
   applying these considerations for processing the signaling messages,
   the specified order MUST be maintained.


5.3.1.  Processing Binding Registrations


   1.   The received Proxy Binding Update message (a Binding Update
        message with the 'P' flag set) MUST be authenticated as
        described in Section 4.  When IPsec is used for message
        authentication, the SPI in the IPsec header [RFC-4306] of the
        received packet is needed for locating the security association,
        for authenticating the Proxy Binding Update message.

   2.   The local mobility anchor MUST observe the rules described in
        Section 9.2 [RFC-3775] when processing Mobility Header in the
        received Proxy Binding Update request.  Additionally, the rules
        specified in Section 10.3 [RFC-3775] MUST be applied when
        processing this message.

   3.   The local mobility anchor MUST ignore the check, specified in
        Section 10.3.1 [RFC-3775], related to the presence of Home



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 18]

Internet-Draft              Proxy Mobile IPv6              February 2008


        Address destination option in the Proxy Binding Update request.

   4.   The local mobility anchor MUST identify the mobile node from the
        identifier present in the Mobile Node Identifier option [RFC-
        4283] of the Proxy Binding Update request.  If the Mobile Node
        Identifier option is not present in the Proxy Binding Update
        request, the local mobility anchor MUST reject the request and
        send a Proxy Binding Acknowledgement message with Status field
        set to MISSING_MN_IDENTIFIER_OPTION (Missing mobile node
        identifier option) and the identifier in the Mobile Node
        Identifier Option carried in the message MUST be set to a zero
        length identifier.

   5.   The local mobility anchor MUST apply the required policy checks,
        as explained in Section 4, to verify the sender is a trusted
        mobile access gateway, authorized to send Proxy Binding Update
        requests on behalf of this mobile node.

   6.   If the local mobility anchor determines that the requesting node
        is not authorized to send Proxy Binding Update requests for the
        identified mobile node, it MUST reject the request and send a
        Proxy Binding Acknowledgement message with Status field set to
        MAG_NOT_AUTHORIZED_FOR_PROXY_REG (not authorized to send proxy
        binding registrations).

   7.   If the local mobility anchor cannot identify the mobile node
        based on the identifier present in the Mobile Node Identifier
        option [RFC-4283] of Proxy Binding Update request, it MUST
        reject the request and send a Proxy Binding Acknowledgement
        message with Status field set to NOT_LMA_FOR_THIS_MOBILE_NODE
        (Not local mobility anchor for this mobile node).

   8.   If the local mobility anchor determines that the mobile node is
        not authorized for the network-based mobility management
        service, it MUST reject the request and send a Proxy Binding
        Acknowledgement message with Status field set to
        PROXY_REG_NOT_ENABLED (Proxy Registration not enabled).

   9.   The local mobility anchor MUST apply the considerations
        specified in Section 5.5, for processing the Sequence Number
        field and the Timestamp option (if present), in the Proxy
        Binding Update request.

   10.  If the Home Network Prefix option (containing either ALL_ZERO or
        some prefix value) is not present in the Proxy Binding Update
        request, the local mobility anchor MUST reject the request and
        send a Proxy Binding Acknowledgement message with Status field
        set to MISSING_HOME_NETWORK_PREFIX_OPTION (Missing home network



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 19]

Internet-Draft              Proxy Mobile IPv6              February 2008


        prefix option).

   11.  If the Handoff Indicator option is not present in the Proxy
        Binding Update request, the local mobility anchor MUST reject
        the request and send a Proxy Binding Acknowledgement message
        with Status field set to MISSING_HANDOFF_INDICATOR_OPTION
        (Missing handoff indicator option).

   12.  If the Access Technology Type option is not present in the Proxy
        Binding Update request, the local mobility anchor MUST reject
        the request and send a Proxy Binding Acknowledgement message
        with Status field set to MISSING_ACCESS_TECH_TYPE_OPTION
        (Missing access technology type option).

   13.  Considerations specified in Section 5.4.1 MUST be applied for
        performing the Binding Cache entry existence test.  If those
        checks specified in Section 5.4.1, result in associating the
        received Proxy Binding Update request to a new mobility session
        creation request, considerations from Section 5.3.2 (Initial
        Binding Registration - New Mobility Session), MUST be applied.
        If those checks result in associating the request to an existing
        mobility session, the following checks determine the next set of
        processing rules that needs to be applied.

        *  If the Handoff Indicator field in the Handoff Indicator
           option present in the request is set to a value of 5 (Handoff
           state not changed), considerations from Section 5.3.3
           (Binding Lifetime Extension- No handoff) MUST be applied.

        *  If the received Proxy Binding Update request has the lifetime
           value of zero, considerations from Section 5.3.5 (Binding De-
           Registration) MUST be applied.

        *  For all other cases, considerations from Section 5.3.4
           (Binding Lifetime Extension - After handoff) MUST be applied.

   14.  When sending the Proxy Binding Acknowledgement message with any
        Status field value, the message MUST be constructed as specified
        in Section 5.3.6.


5.3.2.  Initial Binding Registration (New Mobility Session)

   1.  If the Home Network Prefix option present in the Proxy Binding
       Update request has the value set to ALL_ZERO, the local mobility
       anchor MUST allocate a prefix and assign it to a new mobility
       session created for the mobile node.  The local mobility anchor
       MUST ensure the allocated prefix is not in use by any other node



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 20]

Internet-Draft              Proxy Mobile IPv6              February 2008


       or mobility session.

   2.  If the local mobility anchor is unable to allocate any home
       network prefix for the mobile node, it MUST reject the request
       and send a Proxy Binding Acknowledgement message with Status
       field set to 130 (Insufficient resources).

   3.  If the Home Network Prefix option present in the request has a
       specific prefix hint, the local mobility anchor before accepting
       that request, MUST ensure the prefix is owned by the local
       mobility anchor and further the mobile node is authorized to use
       that prefix.  If the mobile node is not authorized to use that
       prefix, the local mobility anchor MUST reject the request and
       send a Proxy Binding Acknowledgement message with Status field
       set to NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX (Mobile node not
       authorized to use that prefix).

   4.  Upon accepting the request, the local mobility anchor MUST create
       a Binding Cache entry for the mobile node.  It must set the
       fields in the Binding Cache entry to the accepted values for that
       registration.

   5.  The local mobility anchor MUST establish a bi-directional tunnel
       to the mobile access gateway (if there does not exist one) that
       sent the request and setup the routing state.  Considerations
       from Section 5.6 MUST be applied for creating the routing state.

   6.  The local mobility anchor MUST send the Proxy Binding
       Acknowledgement message with the Status field set to 0 (Proxy
       Binding Update Accepted).  The message MUST be constructed as
       specified in Section 5.3.6.


5.3.3.  Binding Lifetime Extension (No handoff)

   1.  Upon accepting the Proxy Binding Update request for extending the
       binding lifetime, received from the same mobile access gateway
       that last updated the binding (i.e., when there is no handoff),
       the local mobility anchor MUST update the Binding Cache entry
       with the accepted registration values.  However, if the link-
       local address value in the Link-local address option is ALL_ZERO
       value, the link-local address field in the Binding Cache entry
       MUST NOT be updated.

   2.  The local mobility anchor MUST send the Proxy Binding
       Acknowledgement message with the Status field set to 0 (Proxy
       Binding Update Accepted).  The message MUST be constructed as
       specified in Section 5.3.6.



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 21]

Internet-Draft              Proxy Mobile IPv6              February 2008


5.3.4.  Binding Lifetime Extension (After handoff)

   1.  Upon accepting the Proxy Binding Update request for extending the
       binding lifetime, received from a new mobile access gateway where
       the mobile node's session is handed off, the local mobility
       anchor MUST update the Binding Cache entry with the accepted
       registration values.  However, if the link-local address value in
       the Link-local address option is ALL_ZERO value, the link-local
       address field in the Binding Cache entry MUST NOT be updated.

   2.  The local mobility anchor MUST remove the previously created
       route for the mobile node's home network prefix.  Additionally,
       if there are no other mobile node's sessions sharing the tunnel
       to the previous mobile access gateway, the tunnel MUST be
       deleted.

   3.  The local mobility anchor MUST establish a bi-directional tunnel
       to the mobile access gateway that sent the request.
       Considerations from Section 5.6 MUST be applied for creating the
       routing state.

   4.  The local mobility anchor MUST send the Proxy Binding
       Acknowledgement message with the Status field set to 0 (Proxy
       Binding Update Accepted).  The message MUST be constructed as
       specified in Section 5.3.6.


5.3.5.  Binding De-Registration

   1.  If the received Proxy Binding Update request with the lifetime
       value of zero, has a Source Address in the IPv6 header (or the
       address in the Alternate Care-of Address option, if the option is
       present) different from what is present in the Proxy-CoA address
       field in the Binding Cache entry, the local mobility anchor MUST
       ignore the request.

   2.  Upon accepting the Proxy Binding Update request with the lifetime
       value of zero, the local mobility anchor MUST wait for
       MinDelayBeforeBCEDelete amount of time, before it deletes the
       Binding Cache entry.  However, it MUST send the Proxy Binding
       Acknowledgement message with the Status field set to 0 (Proxy
       Binding Update Accepted).  The message MUST be constructed as
       specified in Section 5.3.6.

       *  During this wait period, the local mobility anchor SHOULD drop
          the mobile node's data traffic.





Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 22]

Internet-Draft              Proxy Mobile IPv6              February 2008


       *  During this wait period, if the local mobility anchor receives
          a valid Proxy Binding Update request for the same mobility
          session with the lifetime value of greater than zero, and if
          that request is accepted, then the Binding Cache entry MUST
          NOT be deleted, but must be updated with the newly accepted
          registration values and additionally the wait period should be
          ended.

       *  By the end of this wait period, if the local mobility anchor
          did not receive any valid Proxy Binding Update request for
          this mobility session, then it MUST delete the Binding Cache
          entry and remove the routing state created for that mobility
          session.


5.3.6.  Constructing the Proxy Binding Acknowledgement Message

   o  The local mobility anchor when sending the Proxy Binding
      Acknowledgement message to the mobile access gateway MUST
      construct the message as specified below.



          IPv6 header (src=LMAA, dst=Proxy-CoA)
            Mobility header
               - BA    /* P flag must be set */
              Mobility Options
               - Mobile Node Identifier Option           (mandatory)
               - Home Network Prefix option              (mandatory)
               - Handoff Indicator option                (mandatory)
               - Access Technology Type option           (mandatory)
               - Timestamp Option                        (optional)
               - Mobile Node Interface Identifier option (optional)
               - Link-local Address option               (optional)


            Figure 6: Proxy Binding Acknowledgement message format

   o  The Source Address field in the IPv6 header of the message MUST be
      set to the destination address of the received Proxy Binding
      Update request.

   o  The Destination Address field in the IPv6 header of the message
      MUST be set to the source address of the received Proxy Binding
      Update request.  When there is no Alternate Care-of Address option
      present in the request, the destination address is the same as the
      Proxy-CoA address, otherwise, the address may not be the same as
      the Proxy-CoA.



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 23]

Internet-Draft              Proxy Mobile IPv6              February 2008


   o  The Mobile Node Identifier option [RFC-4283] MUST be present.  The
      identifier field in the option MUST be copied from the Mobile Node
      Identifier option in the received Proxy Binding Update request.
      If the option was not present in the request, the identifier in
      the option MUST be set to a zero length identifier.

   o  The Home Network Prefix option MUST be present.

      *  If the Status field is set to a value greater than or equal to
         128, i.e., if the binding request is rejected, then the prefix
         value in the Home Network Prefix option MUST be set to the
         prefix value in the Home Network Prefix option of the received
         Proxy Binding Update request.  But, if the option was not
         present in the request, the value in the option MUST be set to
         ALL_ZERO.

      *  For all other cases, the prefix value in the option MUST be set
         to the allocated prefix value for that mobility session.

   o  The Handoff Indicator option MUST be present.  The handoff
      indicator field in the option MUST be copied from the Handoff
      Indicator option in the received Proxy Binding Update request.  If
      the option was not present in the request, the value in the option
      MUST be set to zero.

   o  The Access Technology Type option MUST be present.  The access
      technology type field in the option MUST be copied from the Access
      Technology Type option in the received Proxy Binding Update
      request.  If the option was not present in the request, the value
      in the option MUST be set to zero.

   o  The Timestamp option MUST be present, if the same option was
      present in the received Proxy Binding Update request.
      Considerations from Section 5.5 must be applied for constructing
      the Timestamp option.

   o  The Mobile Node Interface Identifier option MUST be present, if
      the same option was present in the received Proxy Binding Update
      request.  The interface identifier value MUST be copied from the
      Mobile Node Interface Indicator option present in the received
      Proxy Binding Update request.

   o  The Link-local Address option MUST be present, if the same option
      was present in the received Proxy Binding Update request.

      *  If the received Proxy Binding Update request has the Link-local
         Address option with any value other than ALL_ZERO, the same
         value MUST be copied to the Link-local Address option in the



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 24]

Internet-Draft              Proxy Mobile IPv6              February 2008


         reply.

      *  If there is no existing Binding Cache entry (i.e., if this is a
         request for a new mobility session), or if there is an existing
         Binding Cache entry with the link-local address value set to
         ALL_ZERO, then the link-local address in the option MUST be
         copied from the Link-local Address option present in the
         received Proxy Binding Update request.

      *  For all other cases, the link-local address in the option MUST
         be copied from the Link-local Address field of the Binding
         Cache entry.

   o  If IPsec is used for protecting the signaling messages, the
      message MUST be protected, using the security association existing
      between the local mobility anchor and the mobile access gateway.

   o  Unlike in Mobile IPv6 [RFC-3775], the Type 2 Routing header MUST
      NOT be present in the IPv6 header of the packet.

5.4.  Multihoming Support

   This specification allows mobile nodes to connect to a Proxy Mobile
   IPv6 domain through multiple interfaces and for simultaneous access.
   Following are the key aspects of this multihoming support.

   o  When a mobile node connects to a Proxy Mobile IPv6 domain through
      multiple interfaces and for simultaneous access, the local
      mobility anchor MUST allocate a unique home network prefix for
      each of the connected interfaces.

   o  The local mobility anchor MUST manage each of the allocated home
      network prefixes as part of a separate mobility session, each
      under a separate Binding Cache entry and with its own lifetime.

   o  The local mobility anchor MUST allow for an handoff between two
      different interfaces of the mobile node.  In such a case, the home
      network prefix that is associated with a specific interface
      identifier of a mobile node will be updated with the new interface
      identifier.  The decision on when to create a new mobility session
      and when to update an existing mobility session MUST be based on
      the Handover hint present in the Proxy Binding Update message and
      under the considerations specified in this section.








Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 25]

Internet-Draft              Proxy Mobile IPv6              February 2008


5.4.1.  Binding Cache entry lookup considerations

   There can be multiple Binding Cache entries for a given mobile node.
   When doing a lookup for a mobile node's Binding Cache entry for
   processing a received Proxy Binding Update request message, the local
   mobility anchor MUST apply the following multihoming considerations
   (in the below specified order).  These rules are chained with the
   processing rules specified in Section 5.3.

5.4.1.1.  Home Network Prefix Option (NON_ZERO Value) present in the
          request


 +=====================================================================+
 |                Registration/De-Registration Message                 |
 +=====================================================================+
 |                        HNP (NON_ZERO Value)                         |
 +=====================================================================+
 |                                 ATT                                 |
 +=====================================================================+
 |       IID Option Present         |      IID Option Not present      |
 +=====================================================================+
 |                                 HI                                  |
 +==================================+==================================+
 |                BCE Lookup Key: (Home Network Prefix)                |
 +=====================================================================+


              Figure 7: BCE lookup using home network prefix


   1.  The local mobility anchor MUST verify if there is an existing
       Binding Cache entry with the home network prefix value matching
       the prefix value in the Home Network Prefix option of the
       received Proxy Binding Update request.  [BCE(HNP) == PBU(HNP)]

   2.  If there does not exist a Binding Cache entry (matching the MN-
       HNP), the request MUST be considered as a request for creating a
       new mobility session.

   3.  If there exists a Binding Cache entry (matching MN-HNP), and if
       the mobile node identifier in the entry does not match the mobile
       node identifier in the Mobile Node Identifier option of the
       received Proxy Binding Update request, the local mobility anchor
       MUST reject the request with the Status field value set to
       NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX (mobile node is not
       authorized for the requesting home network prefix).  [BCE(MN-
       Identifier) != PBU(MN-Identifier)]



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 26]

Internet-Draft              Proxy Mobile IPv6              February 2008


   4.  If there exists a Binding Cache entry (matching MN-Identifier and
       MN-HNP) and if any one or more of these below stated conditions
       match, the request MUST be considered as a request for updating
       that Binding Cache entry.  [BCE(MN-Identifier) == PBU(MN-
       Identifier)]

       *  If there is a Mobile Node Interface Identifier option present
          in the request, and if the interface identifier value in that
          option matches the interface identifier value in the Binding
          Cache entry and the access technology type field in the Access
          Technology Type option present in the request matches the
          access technology type in the Binding Cache entry .  [BCE(ATT,
          MN-Interface-Identifier) == PBU(ATT, MN-Interface-Identifier)]

       *  If the Handoff Indicator field in the Handoff Indicator option
          present in the request is set to a value of 2 (Handoff between
          two different interfaces of the mobile node).

       *  If there is no Mobile Node Interface Identifier option present
          in the request, the interface identifier value in the Binding
          Cache entry is set to ALL_ZERO, the access technology type
          field in the Access Technology Type option present in the
          request matches the access technology type in the Binding
          Cache entry and if the Handoff Indicator field in the Handoff
          Indicator option present in the request is set to a value of 3
          (Handoff between mobile access gateways for the same
          interface).

       *  If the Proxy-CoA address in the Binding Cache entry matches
          the source address of the request (or the address in the
          alternate Care-of Address option, if the option is present)
          and if the access technology type field in the Access
          Technology Type option present in the request matches the
          access technology type in the Binding Cache entry.
          [BCE(Proxy-CoA, ATT) == PBU(Proxy-CoA, ATT)].

   5.  For all other cases, the message MUST be considered as a request
       for creating a new mobility session.













Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 27]

Internet-Draft              Proxy Mobile IPv6              February 2008


5.4.1.2.  Mobile Node Interface Identifier Option present in the request



 +=====================================================================+
 |                   Registration/De-Registration Message              |
 +=====================================================================+
 |                          HNP (ALL_ZERO Value)                       |
 +=====================================================================+
 |                                 ATT                                 |
 +=====================================================================+
 |                      IID Option Present (NON_ZERO Value)            |
 +=====================================================================+
 |                                 HI                                  |
 +==================================+==================================+
 | BCE Lookup Keys: (MN-Identifier +  Access Technology Type +         |
 |                   MN-Interface-Identifier)                          |
 +=====================================================================+


              Figure 8: BCE Lookup using Interface Identifier


   1.  The local mobility anchor MUST verify if there is an existing
       Binding Cache entry, with the mobile node identifier matching the
       identifier in the received Mobile Node Identifier option, access
       technology type matching the value in the received Access
       Technology Type option and the interface identifier value
       matching the identifier in the received Mobile Node Interface
       Identifier option.  [BCE(MN-Identifier, ATT, MN-Interface-
       Identifier) == PBU(MN-Identifier, ATT, MN-Interface-Identifier)]

   2.  If there exists a Binding Cache entry (matching MN-Identifier,
       ATT and MN-Interface-Identifier), the request MUST be considered
       as a request for updating that Binding Cache entry.

   3.  If there does not exist a Binding Cache entry (matching MN-
       Identifier, ATT and MN-Interface-Identifier) and the Handoff
       Indicator field in the Handoff Indicator option present in the
       request is set to a value of 2 (Handoff between two different
       interfaces of the mobile node).  The local mobility anchor MUST
       apply the following additional considerations.  [PBU(HI) == 2]

       *  The local mobility anchor MUST verify if there exists one and
          only one Binding Cache entry with the mobile node identifier
          matching the identifier in the Mobile Node Identifier option
          present in the request and for any interface identifier value.
          If there exists only one such entry (matching the MN-



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 28]

Internet-Draft              Proxy Mobile IPv6              February 2008


          Identifier), the request MUST be considered as a request for
          updating that Binding Cache entry.  [BCE(MN-Identifier) ==
          PBU(MN-Identifier)]

   4.  If there does not exist a Binding Cache entry (matching MN-
       Identifier, ATT and MN-Interface-Identifier) and if the Handoff
       Indicator field in the Handoff Indicator option present in the
       request is set to a value of 4 (Handoff state unknown), the local
       mobility anchor MUST apply the following additional
       considerations.

       *  The local mobility anchor MUST verify if there exists one and
          only one Binding Cache entry with the mobile node identifier
          matching the identifier in the Mobile Node Identifier option
          present in the request and for any interface identifier value.
          If there exists only one such entry (matching the MN-
          Identifier), the local mobility anchor SHOULD wait till the
          existing Binding Cache entry is de-registered by the
          previously serving mobile access gateway, before the request
          can be considered as a request for updating that Binding Cache
          entry.  However, if there is no de-registration message that
          is received within MaxDelayBeforeNewBCEAssign amount of time,
          the local mobility anchor upon accepting the request MUST
          consider the request as a request for updating that Binding
          Cache entry.  The local mobility anchor MAY also choose to
          create a new mobility session and without waiting for a de-
          registration message and this should be configurable on the
          local mobility anchor.

   5.  For all other cases, the message MUST be considered as a request
       for creating a new mobility session.




















Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 29]

Internet-Draft              Proxy Mobile IPv6              February 2008


5.4.1.3.  Mobile Node Interface Identifier Option not present in the
          request



 +=====================================================================+
 |                 Registration/De-Registration Message                |
 +=====================================================================+
 |                        HNP (ALL_ZERO Value)                         |
 +=====================================================================+
 |                                 ATT                                 |
 +=====================================================================+
 |                      IID Option Not Present                         |
 +=====================================================================+
 |                                 HI                                  |
 +==================================+==================================+
 |                   BCE Lookup Key: (MN-Identifier)                   |
 +=====================================================================+


             Figure 9: BCE Lookup using Mobile Node Identifier


   1.  The local mobility anchor MUST verify if there exists one and
       only one Binding Cache entry with the mobile node identifier
       matching the identifier in the Mobile Node Identifier option
       present in the request.

   2.  If there exists only one such entry (matching the MN-Identifier)
       and the Handoff Indicator field in the Handoff Indicator option
       present in the request is set to a value of 2 (Handoff between
       two different interfaces of the mobile node), the request MUST be
       considered as a request for updating that Binding Cache entry.
       [PBU(HI) == 2]

   3.  If there exists only one such entry (matching the MN-Identifier)
       and the Handoff Indicator field in the Handoff Indicator option
       present in the request is set to a value of 4 (Handoff state
       unknown), the local mobility anchor SHOULD wait till the existing
       Binding Cache entry is de-registered by the previously serving
       mobile access gateway, before the request can be considered as a
       request for updating that Binding Cache entry.  However, if there
       is no de-registration message that is received within
       MaxDelayBeforeNewBCEAssign amount of time, the local mobility
       anchor upon accepting the request MUST consider the request as a
       request for updating that Binding Cache entry.  The local
       mobility anchor MAY also choose to create a new mobility session
       and without waiting for a de-registration message and this should



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 30]

Internet-Draft              Proxy Mobile IPv6              February 2008


       be configurable on the local mobility anchor.

   4.  For all other cases, the message MUST be considered as a request
       for creating a new mobility session.


5.5.  Timestamp Option for Message Ordering

   Mobile IPv6 [RFC-3775] uses the Sequence Number field in binding
   registration messages as a way for the home agent to process the
   binding updates in the order they were sent by a mobile node.  The
   home agent and the mobile node are required to manage this counter
   over the lifetime of a binding.  However, in Proxy Mobile IPv6, as
   the mobile node moves from one mobile access gateway to another and
   in the absence of mechanisms such as context transfer between the
   mobile access gateways, the serving mobile access gateway will be
   unable to determine the sequence number that it needs to use in the
   signaling messages.  Hence, the sequence number scheme, as specified
   in [RFC-3775], will be insufficient for Proxy Mobile IPv6.

   If the local mobility anchor cannot determine the sending order of
   the received binding registration messages, it may potentially
   process an older message sent by a mobile access gateway where the
   mobile node was previously anchored, resulting in an incorrect
   Binding Cache entry.

   For solving this problem, this specification adopts two alternative
   solutions.  One is based on timestamps and the other based on
   sequence numbers, as defined in [RFC-3775].

   The basic principle behind the use of timestamps in binding
   registration messages is that the node generating the message inserts
   the current time-of-day, and the node receiving the message checks
   that this timestamp is greater than all previously accepted
   timestamps.  The timestamp based solution may be used, when the
   serving mobile access gateways in a Proxy Mobile IPv6 domain do not
   have the ability to obtain the last sequence number that was sent in
   a binding registration message for updating a given mobile node's
   binding.

   As an alternative to the Timestamp based approach, the specification
   also allows the use of Sequence Number based scheme, as per [RFC-
   3775].  However, for this scheme to work, the serving mobile access
   gateways in a Proxy Mobile IPv6 domain MUST have the ability to
   obtain the last sequence number that was sent in a binding
   registration message for updating a given mobile node's binding.  The
   sequence number MUST be maintained on a per mobile node basis and
   MUST be synchronized between the serving mobile access gateways.



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 31]

Internet-Draft              Proxy Mobile IPv6              February 2008


   This may be achieved by using context transfer schemes or by
   maintaining the sequence number in a policy store.  However, the
   specific details on how the mobile node's sequence number is
   synchronized between different mobile access gateways is outside the
   scope of this document.


   Using Timestamps based approach:

   1.  A local mobility anchor implementation MUST support Timestamp
       option.  If the Timestamp option is present in the received Proxy
       Binding Update request message, then the local mobility anchor
       MUST include a valid Timestamp option in the Proxy Binding
       Acknowledgement message that it sends to the mobile access
       gateway.

   2.  All the mobility entities in a Proxy Mobile IPv6 domain that are
       exchanging binding registration messages using the Timestamp
       option must have adequately synchronized time-of-day clocks.
       This is the essential requirement for this solution to work.  If
       this requirement is not met, the solution will not predictably
       work in all cases.

   3.  The mobility entities in a Proxy Mobile IPv6 domain SHOULD
       synchronize their clocks to a common time source.  For
       synchronizing the clocks, the nodes may use Network Time Protocol
       [RFC-4330].  Deployments may also adopt other approaches suitable
       for that specific deployment.  Alternatively, if there is mobile
       node generated timestamp that is increasing at every attachment
       to the access link and if that timestamp is available to the
       mobile access gateway (Ex: The timestamp option in the SEND
       messages that the mobile node sends), the mobile access gateway
       can use this timestamp or sequence number in the Proxy Binding
       Update messages and does not have to depend on any external clock
       source.  However, the specific details on how this is achieved is
       outside the scope of this document.

   4.  When generating the timestamp value for building the Timestamp
       option, the mobility entities MUST ensure that the generated
       timestamp is the elapsed time past the same reference epoch, as
       specified in the format for the Timestamp option [Section 8.8].

   5.  If the Timestamp option is present in the received Proxy Binding
       Update message, the local mobility anchor MUST ignore the
       sequence number field in the message.  However, it MUST copy the
       sequence number from the received Proxy Binding Update message to
       the Proxy Binding Acknowledgement message.




Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 32]

Internet-Draft              Proxy Mobile IPv6              February 2008


   6.  Upon receipt of a Proxy Binding Update message with the Timestamp
       option, the local mobility anchor MUST check the timestamp field
       for validity.  In order for it to be considered valid, the
       timestamp value contained in the Timestamp option MUST be close
       enough (within TimestampValidityWindow amount of time difference)
       to the local mobility anchor's time-of-day clock and the
       timestamp MUST be greater than all previously accepted timestamps
       in the Proxy Binding Update messages sent for that mobile node.

   7.  If the timestamp value in the received Proxy Binding Update is
       valid (validity as specified in the above considerations), the
       local mobility anchor MUST return the same timestamp value in the
       Timestamp option included in the Proxy Binding Acknowledgement
       message that it sends to the mobile access gateway.

   8.  If the timestamp value in the received Proxy Binding Update is
       lower than the previously accepted timestamp in the Proxy Binding
       Update messages sent for that mobility binding, the local
       mobility anchor MUST reject the Proxy Binding Update request and
       send a Proxy Binding Acknowledgement message with Status field
       set to TIMESTAMP_LOWER_THAN_PREV_ACCEPTED (Timestamp lower than
       previously accepted timestamp).  The message MUST also include
       the Timestamp option with the value set to the current time-of-
       day on the local mobility anchor.

   9.  If the timestamp value in the received Proxy Binding Update is
       not valid (validity as specified in the above considerations),
       the local mobility anchor MUST reject the Proxy Binding Update
       and send a Proxy Binding Acknowledgement message with Status
       field set to TIMESTAMP_MISMATCH (Timestamp mismatch).  The
       message MUST also include the Timestamp option with the value set
       to the current time-of-day on the local mobility anchor.


   Using Sequence Number based approach:

   1.  If the Timestamp option is not present in the received Proxy
       Binding Update request, the local mobility anchor MUST fallback
       to the Sequence Number based scheme.  It MUST process the
       sequence number field as specified in [RFC-3775].  Also, it MUST
       NOT include the Timestamp option in the Proxy Binding
       Acknowledgement messages that it sends to the mobile access
       gateway.

   2.  An implementation MUST support Sequence Number based scheme, as
       per [RFC-3775].





Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 33]

Internet-Draft              Proxy Mobile IPv6              February 2008


5.6.  Routing Considerations

5.6.1.  Bi-Directional Tunnel Management


   o  A bi-directional tunnel MUST be established between the local
      mobility anchor and the mobile access gateway with IP-in-IP
      encapsulation, as described in [RFC-2473].  The tunnel end points
      are the Proxy-CoA and LMAA.  When using IPv4 transport with a
      specific encapsulation mode, the end points of the tunnel are the
      IPv4-LMAA and IPv4-Proxy-CoA, as specified in [ID-IPV4-PMIP6].

   o  The bi-directional tunnel MUST be used for routing the mobile
      node's data traffic between the mobile access gateway and the
      local mobility anchor.  The tunnel hides the topology and enables
      a mobile node to use an address from its home network prefix from
      any access link attached to the mobile access gateway.

   o  The bi-directional tunnel is established after accepting the Proxy
      Binding Update request message.  The created tunnel may be shared
      with other mobile nodes attached to the same mobile access gateway
      and with the local mobility anchor having a Binding Cache entry
      for those mobile nodes.  Implementations MAY choose to use static
      tunnels instead of dynamically creating and tearing them down on a
      need basis.

   o  Implementations MAY use a software timer for managing the tunnel
      lifetime and a counter for keeping a count of all the mobile nodes
      that are sharing the tunnel.  The timer value MUST be set to the
      accepted binding lifetime and will be updated after each periodic
      re-registration for extending the lifetime.  If the tunnel is
      shared for multiple mobile nodes, the tunnel lifetime MUST be set
      to the highest binding lifetime that is granted to any one of
      those mobile nodes sharing that tunnel.

5.6.2.  Forwarding Considerations

   Intercepting Packets Sent to the Mobile Node's Home Network:

   o  When the local mobility anchor is serving a mobile node, it MUST
      be able to receive packets that are sent to the mobile node's home
      network.  In order for it to receive those packets, it MUST
      advertise a connected route in to the Routing Infrastructure for
      the mobile node's home network prefix or for an aggregated prefix
      with a larger scope.  This essentially enables IPv6 routers in
      that network to detect the local mobility anchor as the last-hop
      router for that prefix.




Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 34]

Internet-Draft              Proxy Mobile IPv6              February 2008


   Forwarding Packets to the Mobile Node:

   o  On receiving a packet from a correspondent node with the
      destination address matching a mobile node's home network prefix,
      the local mobility anchor MUST forward the packet through the bi-
      directional tunnel setup for that mobile node.  The format of the
      tunneled packet is shown below.  However, when using IPv4
      transport, the format of the packet is as described in [ID-IPV4-
      PMIP6].


        IPv6 header (src= LMAA, dst= Proxy-CoA  /* Tunnel Header */
           IPv6 header (src= CN, dst= MN-HOA )  /* Packet Header */
              Upper layer protocols             /* Packet Content*/



                 Figure 10: Tunneled Packets from LMA to MAG


   Forwarding Packets Sent by the Mobile Node:

   o  All the reverse tunneled packets that the local mobility anchor
      receives from the mobile access gateway, after removing the tunnel
      header MUST be routed to the destination specified in the inner
      packet header.  These routed packets will have the source address
      field set to the mobile node's home address.

5.7.  Local Mobility Anchor Address Discovery

   Dynamic Home Agent Address Discovery, as explained in Section 10.5
   [RFC-3775], allows a mobile node to discover all the home agents on
   its home link by sending an ICMP Home Agent Address Discovery Request
   message to the Mobile IPv6 Home-Agents anycast address, derived from
   its home network prefix.

   The DHAAD message in the current form cannot be used in Proxy Mobile
   IPv6 for discovering the address of the mobile node's local mobility
   anchor.  In Proxy Mobile IPv6, the local mobility anchor will not be
   able to receive any messages sent to the Mobile IPv6 Home-Agents
   anycast address corresponding to the mobile node's home network
   prefix, as the prefix is not hosted on any of its interfaces.
   Further, the mobile access gateway will not predictably be able to
   locate the serving local mobility anchor that has the mobile node's
   binding cache entry.  Hence, this specification does not support
   Dynamic Home Agent Address Discovery protocol.

   In Proxy Mobile IPv6, the address of the local mobility anchor



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 35]

Internet-Draft              Proxy Mobile IPv6              February 2008


   configured to serve a mobile node can be discovered by the mobility
   entities in other ways.  This may be a configured entry in the mobile
   node's policy profile, or it may be obtained through mechanisms
   outside the scope of this document.

5.8.  Mobile Prefix Discovery Considerations

   This specification does not support mobile prefix discovery.  The
   mobile prefix discovery mechanism as specified in [RFC-3775] is not
   applicable to Proxy Mobile IPv6.

5.9.  Route Optimizations Considerations

   The Route Optimization in Mobile IPv6, as defined in [RFC-3775],
   enables a mobile node to communicate with a correspondent node
   directly using its care-of address and further the Return Routability
   procedure enables the correspondent node to have reasonable trust
   that the mobile node is reachable at both its home address and
   care-of address.

   In Proxy Mobile IPv6, the mobile node is not involved in any IP
   mobility related signaling.  The mobile node uses only its home
   address for all its communication and the Care-of address (Proxy-CoA)
   is not visible to the mobile node.  Hence, the Return Routability
   procedure as defined in Mobile IPv6 [RFC-3775] cannot be used in
   Proxy Mobile IPv6.


6.  Mobile Access Gateway Operation

   The Proxy Mobile IPv6 protocol described in this document introduces
   a new functional entity, the Mobile Access Gateway (MAG).  The mobile
   access gateway is the entity that is responsible for detecting the
   mobile node's movements to and from the access link and sending the
   binding registration requests to the local mobility anchor.  In
   essence, the mobile access gateway performs mobility management on
   behalf of a mobile node.

   The mobile access gateway is a function that typically runs on an
   access router.  However, implementations MAY choose to split this
   function and run it across multiple systems.  The specifics on how
   that is achieved or the signaling interactions between those
   functional entities are beyond the scope of this document.

   The mobile access gateway has the following key functional roles:

   o  It is responsible for detecting the mobile node's movements on the
      access link and for initiating the mobility signaling with the



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 36]

Internet-Draft              Proxy Mobile IPv6              February 2008


      mobile node's local mobility anchor.

   o  Emulation of the mobile node's home link on the access link by
      sending Router Advertisements with the mobile node's home network
      prefix information.

   o  Responsible for setting up the data path for enabling the mobile
      node to configure an address from its home network prefix and use
      it from its access link.

6.1.  Extensions to Binding Update List Entry Data Structure

   Every mobile access gateway MUST maintain a Binding Update List.
   Each entry in the Binding Update List represents a mobile node's
   mobility binding with its local mobility anchor.  The Binding Update
   List is a conceptual data structure, described in Section 11.1 [RFC-
   3775].

   For supporting this specification, the conceptual Binding Update List
   entry data structure needs be extended with the following additional
   fields.


   o  The Identifier of the attached mobile node, MN-Identifier.  This
      identifier is acquired during the mobile node's attachment to the
      access link through mechanisms outside the scope of this document.

   o  The interface identifier of the mobile node's connected interface.
      This address can be acquired from the received Router Solicitation
      messages from the mobile node or during the mobile node's
      attachment to the access network.  This is typically a Layer-2
      identifier conveyed by the mobile node; however, the specific
      details on how that is conveyed is out of scope for this
      specification.  If this identifier is not available, the value
      MUST be set to ALL_ZERO.

   o  The IPv6 home network prefix of the attached mobile node.  The
      home network prefix of the mobile node is acquired from the mobile
      node's local mobility anchor through the received Proxy Binding
      Acknowledgement messages.  The IPv6 home network prefix also
      includes the corresponding prefix length.

   o  The Link-local address of the mobile node on the interface
      attached to the access link.

   o  The IPv6 address of the local mobility anchor serving the attached
      mobile node.  This address is acquired from the mobile node's
      policy profile or from other means.



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 37]

Internet-Draft              Proxy Mobile IPv6              February 2008


   o  The interface identifier (If-Id) of the access link where the
      mobile node is currently attached.  This is internal to the mobile
      access gateway and is used to associate the Proxy Mobile IPv6
      tunnel to the access link where the mobile node is attached.

   o  The interface identifier (If-Id) of the bi-directional tunnel
      between the mobile node's local mobility anchor and the mobile
      access gateway.  This is internal to the mobile access gateway.
      The tunnel interface identifier is acquired during the tunnel
      creation.

6.2.  Mobile Node's Policy Profile

   A mobile node's policy profile contains the essential operational
   parameters that are required by the network entities for managing the
   mobile node's mobility service.  These policy profiles are stored in
   a local or a remote policy store.  The mobile access gateway and the
   local mobility anchor MUST be able to obtain a mobile node's policy
   profile.  The policy profile MAY also be handed over to a serving
   mobile access gateway as part of a context transfer procedure during
   a handoff or the serving mobile access gateway MAY be able to
   dynamically generate this profile.  The exact details on how this
   achieved is outside the scope of this document.  However, this
   specification requires that a mobile access gateway serving a mobile
   node MUST have access to its policy profile.

   The following are the mandatory fields of the policy profile:

   o  The mobile node's identifier (MN-Identifier)

   o  The IPv6 address of the local mobility anchor (LMAA)


   The following are the optional fields of the policy profile:

   o  The mobile node's IPv6 home network prefix (MN-HNP)

   o  The mobile node's IPv6 home network Prefix lifetime

   o  Supported address configuration procedures (Stateful, Stateless or
      both) for the mobile node in the Proxy Mobile IPv6 domain


6.3.  Supported Access Link Types

   This specification supports only point-to-point access link types and
   thus it assumes that the mobile node and the mobile access gateway
   are the only two nodes on the access link.  The link is assumed to



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 38]

Internet-Draft              Proxy Mobile IPv6              February 2008


   have multicast capability.  This protocol may also be used on other
   link types, as long as the link is configured in such a way that it
   guarantees a point-to-point delivery between the mobile node and the
   mobile access gateway for all the protocol traffic.

6.4.  Supported Address Configuration Modes

   A mobile node in the Proxy Mobile IPv6 domain can configure one or
   more IPv6 addresses on its interface using Stateless or Stateful
   address autoconfiguration procedures.  The Router Advertisement
   messages sent on the access link specify the address configuration
   methods permitted on that access link for that mobile node.  However,
   the advertised flags with respect to the address configuration will
   be consistent for a mobile node, on any of the access links in that
   Proxy Mobile IPv6 domain.  Typically, these configuration settings
   will be based on the domain wide policy or based on a policy specific
   to each mobile node.

   When stateless address autoconfiguration is supported on the access
   link, the mobile node can generate one or more IPv6 addresses by
   standard IPv6 mechanisms such as Stateless Autoconfiguration
   specification [RFC-4862] or Privacy extension specification [RFC-
   4941].

   When stateful address autoconfiguration is supported on the link, the
   mobile node can obtain the address configuration from the DHCPv6
   server by standard DHCPv6 mechanisms, as specified in DHCPv6
   specification [RFC-3315].

   Additionally, other address configuration mechanisms specific to the
   access link between the mobile node and the mobile access gateway may
   also be used for pushing the address configuration to the mobile
   node.  This specification does not change the behavior of address
   configuration mechanisms in any way.

6.5.  Access Authentication & Mobile Node Identification

   When a mobile node attaches to an access link connected to the mobile
   access gateway, the deployed access security protocols on that link
   SHOULD ensure that the network-based mobility management service is
   offered only after authenticating and authorizing the mobile node for
   that service.  The exact specifics on how this is achieved or the
   interactions between the mobile access gateway and the access
   security service is outside the scope of this document.  This
   specification goes with the stated assumption of having an
   established trust between the mobile node and the mobile access
   gateway, before the protocol operation begins.




Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 39]

Internet-Draft              Proxy Mobile IPv6              February 2008


6.6.  Acquiring Mobile Node's Identifier

   All the network entities in a Proxy Mobile IPv6 domain MUST be able
   to identify a mobile node, using its MN-Identifier.  This identifier
   MUST be stable across the Proxy Mobile IPv6 domain and the entities
   must be able to use this identifier in the signaling messages.
   Typically, this identifier is obtained as part of the access
   authentication or through other means as specified below.

   o  The identifier of the mobile node that the mobile access gateway
      obtains typically as part of the access authentication or from the
      notified network attachment event, can be a temporary identifier
      and further that temporary identifier may be different at each re-
      authentication.  The mobile access gateway MUST be able to use
      this temporary identifier and obtain the mobile node's stable
      identifier from the policy store.  For instance, in AAA-based
      systems the RADIUS attribute, Chargeable-User-Identifier [RFC-
      4372] may be used.

   o  The MN-Identifier that the policy store delivers to the mobile
      access gateway may not be the true identifier of the mobile node.
      However, the mobility access gateway MUST be able to use this
      identifier in the signaling messages exchanged with the local
      mobility anchor.

   o  The mobile access gateway MUST be able to identify the mobile node
      by its MN-Identifier and it MUST be able to associate this
      identity to the point-to-point link shared with the mobile node.

6.7.  Home Network Emulation

   One of the key functions of a mobile access gateway is to emulate the
   mobile node's home network on the access link.  It must ensure, the
   mobile node believes it is still connected to its home link or on the
   link where it obtained its initial address configuration after it
   moved into that Proxy Mobile IPv6 domain.

   For emulating the mobile node's home link on the access link, the
   mobile access gateway must be able to send Router Advertisements
   advertising the mobile node's home network prefix and other address
   configuration parameters consistent with its home link properties.
   Typically, these configuration settings will be based on the domain
   wide policy or based on a policy specific to each mobile node.

   Typically, the mobile access gateway learns the mobile node's home
   network prefix information from the received Proxy Binding
   Acknowledgement message or it may be obtained from the mobile node's
   policy profile.  However, the mobile access gateway SHOULD send the



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 40]

Internet-Draft              Proxy Mobile IPv6              February 2008


   Router Advertisements advertising the mobile node's home network
   prefix only after successfully completing the binding registration
   with the mobile node's local mobility anchor.

   When advertising the home network prefix in the Router Advertisement
   messages, the mobile access gateway MAY set the prefix lifetime value
   for the advertised prefix to any chosen value at its own discretion.
   An implementation MAY choose to tie the prefix lifetime to the mobile
   node's binding lifetime.  The prefix lifetime can also be an optional
   configuration parameter in the mobile node's policy profile.

6.8.  Link-Local and Global Address Uniqueness

   A mobile node in the Proxy Mobile IPv6 domain, as it moves from one
   mobile access gateway to the other, will continue to detect its home
   network and thus making it believe it is still on the same link.
   Every time the mobile node attaches to a new link, the event related
   to the interface state change will trigger the mobile node to perform
   DAD operation on the link-local and global addresses.  However, if
   the mobile node is DNAv6 enabled, as specified in [ID-DNAV6], it may
   not detect the link change due to DNAv6 optimizations and may not
   trigger the duplicate address detection (DAD) procedure for
   establishing the link-local address uniqueness on that new link.
   This leaves a room for link-local address collision between the two
   neighbors on that access link.

   For solving this problem, this specification allows the mobile access
   gateway to upload the mobile node's link-local address to the local
   mobility anchor using the Link-local Address option, exchanged in the
   binding registration messages.  The mobile access gateway can learn
   the mobile node's link-local address, by snooping the DAD messages
   sent by the mobile node for establishing the link-local address
   uniqueness on the access link.  Subsequently, at each handoff, the
   mobile access gateway can obtain this address from the local mobility
   anchor to ensure link-local address uniqueness and change its own
   link-local address, if it detects a collision.

   Alternatively, one of the workarounds for this issue is to set the
   DNAv6 configuration parameter, DNASameLinkDADFlag to TRUE and that
   will force the mobile node to redo DAD operation on the global and
   link-local addresses every time the interface detects an handoff,
   even when DNAv6 does not detect a link change.

   However, this issue may not impact point-to-point links based on PPP.
   Each time the mobile node moves and attaches to a new mobile access
   gateway, the PPP session [RFC-1661] can be re-established, or if
   there are context transfer procedures in place, the entire PPP
   session can be moved to the new link and the link-local addresses of



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 41]

Internet-Draft              Proxy Mobile IPv6              February 2008


   both the peers will continue to remain the same.  In either of these
   approaches, the link-local address uniqueness on the link is assured.
   The specific details of how the PPP session is re-established without
   impacting any layer-3 sessions or how the PPP session can be moved
   between the mobile access gateways is outside the scope of this
   document.

   The issue of address collision is not relevant to the mobile node's
   global address.  Since there is a unique home network prefix assigned
   for each mobile node, the uniqueness for the mobile node's global
   address is assured on the access link.

6.9.  Signaling Considerations

6.9.1.  Binding Registrations

6.9.1.1.  Mobile Node Attachment and Initial Binding Registration

   1.   After detecting a new mobile node on its access link, the mobile
        access gateway MUST identify the mobile node and acquire its MN-
        Identifier.  If it determines that the network-based mobility
        management service needs to be offered to the mobile node, it
        MUST send a Proxy Binding Update message to the local mobility
        anchor.

   2.   The Proxy Binding Update message MUST include the Mobile Node
        Identifier option [RFC-4283], carrying the MN-Identifier for
        identifying the mobile node.

   3.   The Home Network Prefix option MUST be present in the Proxy
        Binding Update message.  If the mobile access gateway learns the
        mobile node's home network prefix either from its policy store
        or from other means, the mobile access gateway MAY choose to
        specify the same in the Home Network Prefix option for
        requesting the local mobility anchor to allocate that prefix,
        otherwise it MUST specify a value of ALL_ZERO.  If the specified
        value is ALL_ZERO, then the local mobility anchor will do the
        prefix assignment.

   4.   The Handoff Indicator option MUST be present in the Proxy
        Binding Update message.  The Handoff Indicator field in the
        Handoff Indicator option MUST be set to a value indicating the
        handoff hint.

        *  The Handoff Indicator field MUST be set to value 1
           (Attachment over a new interface), if the mobile access
           gateway predictably knows that the mobile node's current
           attachment to the network over this interface is not as a



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 42]

Internet-Draft              Proxy Mobile IPv6              February 2008


           result of an handoff of an existing mobility session (over
           the same interface or through a different interface), but as
           a result of an attachment over a new interface.  This
           essentially serves as a request to the local mobility anchor
           to create a new mobility session and not update any existing
           Binding Cache entry created for the same mobile node
           connected to the Proxy Mobile IPv6 domain through a different
           interface.

        *  The Handoff Indicator field MUST be set to value 2 (Handoff
           between two different interfaces of the mobile node), if the
           mobile access gateway definitively knows the mobile node's
           current attachment is due to an handoff of an existing
           mobility session, between two different interfaces of the
           mobile node.

        *  The Handoff Indicator field MUST be set to value 3 (Handoff
           between mobile access gateways for the same interface), if
           the mobile access gateway definitively knows the mobile
           node's current attachment is due to an handoff of an existing
           mobility session between two mobile access gateways and for
           the same interface of the mobile node.

        *  The Handoff Indicator field MUST be set to value 4 (Handoff
           state unknown), if the mobile access gateway cannot determine
           if the mobile node's current attachment is due to an handoff
           of an existing mobility session.

   5.   The mobile access gateway MUST apply the below considerations
        when choosing the value for the Handoff Indicator field.

        *  The mobile access gateway can choose to use the value 2
           (Handoff between two different interfaces of the mobile
           node), only when it knows that the mobile node has on purpose
           switched from one interface to another, and the previous
           interface is going to be disabled.  It may know this due to a
           number of factors.  For instance, most cellular networks have
           controlled handovers where the network knows that the host is
           moving from one attachment to another.  In this situation the
           link layer mechanism can inform the mobility functions that
           this is indeed a movement, not a new attachment.

        *  Some link layers have interface identifiers that can be used
           to distinguish (a) the movement of a particular interface to
           a new attachment from (b) the attachment of new interface
           from the same host.  Option value 3 (Handoff between mobile
           access gateways for the same interface)is appropriate in case
           a and value of 1 (Attachment over a new interface) in case b.



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 43]

Internet-Draft              Proxy Mobile IPv6              February 2008


        *  The mobile access gateway MUST NOT set the option value to 2
           (Handoff between two different interfaces of the mobile node)
           or 3 (Handoff between mobile access gateways for the same
           interface) if it can not be determined that the mobile node
           can move the address between the interfaces involved in the
           handover or that it is the same interface that has moved.
           Otherwise Proxy Mobile IPv6-unaware hosts that have multiple
           physical interfaces to the same domain may suffer unexpected
           failures.

        *  Where no support from link-layer exists, the host and the
           network would need to inform each other about the intended
           movement.  Proxy Mobile IPv6 protocol does not specify this
           and simply requires that knowledge about movements can be
           derived either from the link-layer or from somewhere else.
           The method by which this is accomplished is outside the scope
           of this specification.

   6.   Either the Timestamp option or a valid sequence number
        maintained on a per mobile node basis (if Sequence Number based
        scheme is in use) MUST be present.  When Timestamp option is
        added to the message, the mobile access gateway SHOULD also set
        the Sequence Number field to a value of a monotonically
        increasing counter (not to be confused with the per mobile node
        sequence number specified [RFC-3775]).  The local mobility
        anchor will ignore this field when there is a Timestamp option
        present in the request, but will return the same value in the
        Proxy Binding Acknowledgement message.  This will be useful for
        matching the reply to the request message.

   7.   The Mobile Node Interface Identifier option carrying the
        interface identifier of the currently attached interface MUST be
        present in the Proxy Binding Update message, if the mobile
        access gateway knows the interface identifier of the mobile
        node's currently attached interface.  If the interface
        identifier is not known or if the identifier value is ALL_ZERO,
        this option MUST NOT be present.

   8.   The Access Technology Type option MUST be present in the Proxy
        Binding Update message.  The access technology type field in the
        option SHOULD be set to the type of access technology using
        which the mobile node is currently attached to the mobile access
        gateway.

   9.   The Link-local Address option MAY be present in the Proxy
        Binding Update message.  Considerations from Section 6.8 MUST be
        applied when using the link-local address option.




Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 44]

Internet-Draft              Proxy Mobile IPv6              February 2008


        *  When uploading the link-local address to the local mobility
           anchor, the value in the option MUST be set to the link-local
           address that is configured on the currently attached
           interface of the mobile node.

        *  When querying the local mobility anchor for the mobile node's
           link-local address, the option MUST be set to ALL_ZERO value.
           This essentially serves as a request to the local mobility
           anchor to return the link-local address of the mobile node
           from the binding cache entry corresponding to this mobility
           session.

   10.  The Proxy Binding Update message MUST be constructed as
        specified in Section 6.9.1.5.

   11.  If there is no existing Binding Update List entry for that
        mobile node, the mobile access gateway MUST create a Binding
        Update List entry for the mobile node upon sending the Proxy
        Binding Update request.


6.9.1.2.  Receiving Binding Registration Reply

   On receiving a Proxy Binding Acknowledgement message from the local
   mobility anchor, the mobile access gateway MUST process the message
   as specified below.


   1.   The received Proxy Binding Acknowledgement message (a Binding
        Acknowledgement message with the 'P' flag set) MUST be
        authenticated as described in Section 4.  When IPsec is used for
        message authentication, the SPI in the IPsec header [RFC-4306]
        of the received packet is needed for locating the security
        association, for authenticating the Proxy Binding
        Acknowledgement message .

   2.   The mobile access gateway MUST observe the rules described in
        Section 9.2 [RFC-3775] when processing Mobility Headers in the
        received Proxy Binding Acknowledgement message.

   3.   The mobile access gateway MUST apply the considerations
        specified in Section 5.5 for processing the Sequence Number
        field and the Timestamp option (if present), in the message.

   4.   The mobile access gateway MUST ignore any checks, specified in
        [RFC-3775] related to the presence of Type 2 Routing header in
        the Proxy Binding Acknowledgement message.




Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 45]

Internet-Draft              Proxy Mobile IPv6              February 2008


   5.   The mobile access gateway MAY use the mobile node identifier
        present in the Mobile Node Identifier option for matching the
        response to the request messages that it sent recently .
        However, if there are more than one request message in its
        request queue for the same mobile node, the sequence number
        field can be used for identifying the exact message from those
        messages.  There are other ways to achieve this and
        implementations are free to adopt the best approach that suits
        their implementation.  Additionally, if the received Proxy
        Binding Acknowledgement message does not match any of the Proxy
        Binding Update messages that it sent recently, the message MUST
        be ignored.

   6.   If the received Proxy Binding Acknowledgement message has any
        one or more of the following options, Handoff Indicator option,
        Access Technology Type option, Mobile Node Interface Identifier
        option, Mobile Node Identifier option, carrying option values
        that are different from the option values present in the
        corresponding request (Proxy Binding Update) message, the
        message MUST be ignored as the local mobility anchor is expected
        to echo back all these listed options and with the same option
        values in the reply message.  Further, the mobile access gateway
        MUST NOT retransmit the Proxy Binding Update message till an
        administrative action is taken.

   7.   If the received Proxy Binding Acknowledgement message has the
        Status field value set to PROXY_REG_NOT_ENABLED (Proxy
        registration not enabled for the mobile node), the mobile access
        gateway SHOULD NOT send binding registration requests again for
        that mobile node.  It MUST deny the mobility service to that
        mobile node.

   8.   If the received Proxy Binding Acknowledgement message has the
        Status field value set to TIMESTAMP_LOWER_THAN_PREV_ACCEPTED
        (Timestamp value lower than previously accepted value), the
        mobile access gateway SHOULD try to register again to reassert
        the mobile node's presence on its access link.  The mobile
        access gateway is not specifically required to synchronize its
        clock upon receiving this error code.

   9.   If the received Proxy Binding Acknowledgement message has the
        Status field value set to TIMESTAMP_MISMATCH (Invalid timestamp
        value), the mobile access gateway SHOULD try to register again
        only after it has synchronized its clock to a common time source
        that is used by all the mobility entities in that domain for
        their clock synchronization.  The mobile access gateway SHOULD
        NOT synchronize its clock to the local mobility anchor's system
        clock, based on the timestamp present in the received message.



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 46]

Internet-Draft              Proxy Mobile IPv6              February 2008


   10.  If the received Proxy Binding Acknowledgement message has the
        Status field value set to NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX
        (mobile node is not authorized for the requesting home network
        prefix), the mobile access gateway SHOULD NOT request for the
        same prefix again, but can request the local mobility anchor to
        dynamically assign a prefix, by specifying a ALL_ZERO value in
        the Home Network Prefix option carried in the subsequent Proxy
        Binding Update message.

   11.  If the received Proxy Binding Acknowledgement message has the
        Status field value set to any value greater than or equal to 128
        (i.e., if the binding is rejected), the mobile access gateway
        MUST NOT advertise the mobile node's home network prefix in the
        Router Advertisements sent on that access link and there by
        denying mobility service to the mobile node.

   12.  If the received Proxy Binding Acknowledgement message has the
        Status field value set to 0 (Proxy Binding Update accepted), the
        mobile access gateway MUST update the routing state, as
        explained in section 6.10, and MUST also update the Binding
        Update List entry for reflecting the accepted binding
        registration status.

   13.  If the received Proxy Binding Acknowledgement message has the
        address in the Link-local Address option set to a value that
        matches its own link-local address on that access interface
        where the mobile node is anchored, the mobile access gateway
        MUST change its link-local address on that interface, to avoid
        link-local address collision on that access link.


6.9.1.3.  Extending Binding Lifetime

   1.  For extending the lifetime of a currently registered mobile node
       (i.e., after a successful initial binding registration from the
       same mobile access gateway), the mobile access gateway can send a
       Proxy Binding Update message to the local mobility anchor with a
       new lifetime value.  This re-registration message MUST be
       constructed with the same set of options as the initial binding
       registration message, under the considerations specified in
       Section 6.9.1.1.  However the following exceptions apply.

   2.  The prefix value in the Home Network Prefix option MUST be set to
       the currently assigned home network prefix.

   3.  The Handoff Indicator field in the Handoff Indicator option MUST
       be set to a value of 5 (Handoff state not changed - Re-
       Registration).



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 47]

Internet-Draft              Proxy Mobile IPv6              February 2008


   4.  The value in the Link-local Address option (if the option was
       present in the initial registration message) MUST be set to the
       link-local address of the mobile node's attached interface.


6.9.1.4.  Mobile Node Detachment and Binding De-Registration

   1.  At any point, the mobile access gateway detects that the mobile
       node has moved away from its access link, or if it decides to
       terminate the mobile node's mobility session, it SHOULD send a
       Proxy Binding Update message to the local mobility anchor with
       the lifetime value set to zero.  This de-registration message
       MUST be constructed with the same set of options as the initial
       binding registration message, under the considerations specified
       in Section 6.9.1.1.  However, the following exceptions apply.

   2.  The prefix value in the Home Network Prefix option MUST be set to
       the currently assigned home network prefix.

   3.  The Handoff Indicator field in the Handoff Indicator option MUST
       be set to a value of 4 (Handoff state unknown).

   4.  The value in the Link-local Address option (if the option was
       present in the initial registration message) MUST be set to the
       link-local address of the mobile node's attached interface.

   Either upon receipt of a Proxy Binding Acknowledgement message from
   the local mobility anchor or after INITIAL_BINDINGACK_TIMEOUT [RFC-
   3775] timeout waiting for the reply, the mobile access gateway MUST
   do the following:

   1.  It MUST remove the Binding Update List entry for the mobile node
       from its Binding Update List.

   2.  It MUST withdraw the mobile node's home network prefix as the
       hosted on-link prefix, by sending a Router Advertisement message
       with the prefix lifetime value set to zero.

   3.  It MUST remove the created routing state for tunneling the mobile
       node's traffic.

   4.  It SHOULD teardown the point-to-point link shared with the mobile
       node.  This action will force the mobile node to remove any IPv6
       address configuration on the interface connected to this point-
       to-point link.






Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 48]

Internet-Draft              Proxy Mobile IPv6              February 2008


6.9.1.5.  Constructing the Proxy Binding Update Message

   o  The mobile access gateway when sending the Proxy Binding Update
      request to the local mobility anchor MUST construct the message as
      specified below.


          IPv6 header (src=Proxy-CoA, dst=LMAA)
            Mobility header
               - BU /* P & A flags MUST be set */
              Mobility Options
               - Mobile Node Identifier option           (mandatory)
               - Home Network Prefix option              (mandatory)
               - Handoff Indicator option                (mandatory)
               - Access Technology Type option           (mandatory)
               - Timestamp option                        (optional)
               - Mobile Node Interface Identifier option (optional)
               - Link-local Address option               (optional)


                Figure 11: Proxy Binding Update message format

   o  The Source Address field in the IPv6 header of the message MUST be
      set to the address configured on the interface of the mobile
      access gateway.  When there is no Alternate Care-of Address option
      present in the request, this address will be considered as the
      Proxy-CoA address for this binding registration request.  However,
      when there is Alternate Care-of Address option present in the
      request, this address will be not be the considered as the Proxy-
      CoA address, but the address in the alternate Care-of Address
      option will be considered as the Proxy-CoA address.

   o  The Destination Address field in the IPv6 header of the message
      MUST be set to the local mobility anchor address.

   o  The Mobile Node Identifier option [RFC-4283] MUST be present.

   o  The Home Network Prefix option MUST be present.

   o  The Handoff Indicator option MUST be present.

   o  The Access Technology Type option MUST be present.

   o  The Timestamp option MAY be present.

   o  The Mobile Node Interface Identifier option MAY be present.





Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 49]

Internet-Draft              Proxy Mobile IPv6              February 2008


   o  The Link-local Address option MAY be present.

   o  If IPsec is used for protecting the signaling messages, the
      message MUST be protected, using the security association existing
      between the local mobility anchor and the mobile access gateway.

   o  Unlike in Mobile IPv6 [RFC-3775], the Home Address option [RFC-
      3775] MUST NOT be present in the IPv6 Destination Options
      extension header of the Proxy Binding Update message.

6.9.2.  Router Solicitation Messages

   The mobile node may send a Router Solicitation message on the access
   link whenever the link-layer detects a media change.  The Source
   Address in the IPv6 header of the Router Solicitation message may
   either be the link-local address of the mobile node or an unspecified
   address (::).  The Router Solicitation message that the mobile node
   sends is as specified in [RFC-4861].


   1.  The mobile access gateway on receiving the Router Solicitation
       message SHOULD send a Router Advertisement containing the mobile
       node's home network prefix as the on-link prefix.  However,
       before sending the Router Advertisement message containing the
       mobile node's home network prefix, it SHOULD complete the binding
       registration process with the mobile node's local mobility
       anchor.

   2.  If the local mobility anchor rejects the binding registration
       request, or, if the mobile access gateway failed to complete the
       binding registration process for whatever reasons, the mobile
       access gateway MUST NOT advertise the mobile node's home network
       prefix in the Router Advertisement messages that it sends on the
       access link.  However, it MAY choose to advertise a local visited
       network prefix to enable the mobile node for regular IPv6 access.

6.9.3.  Default-Router Lifetime

   In Proxy Mobile IPv6, the mobile access gateway is typically the IPv6
   default-router for the mobile node on the access link, as it is the
   entity that sends the Router Advertisements on the access link.
   However, as the mobile node moves from one access link to another,
   the serving mobile access gateway on those respective links will send
   the Router Advertisements and using their own link-local address.
   The mobile node on each of the attached links will receive Router
   Advertisement messages with a different source address and this makes
   the mobile node believe that there is a new default-router on that
   access link.



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 50]

Internet-Draft              Proxy Mobile IPv6              February 2008


   The mobile node will certainly detect the previous default-router
   loss by performing the Neighbor Unreachability Detection procedure
   per the standard IPv6 ND mechanisms, but it is important that the
   mobile access gateway enables the mobile node to withdraw the
   previous default-router entry at the earliest.  This action will help
   in minimizing packet losses during a hand off switch.  Following are
   some considerations that implementations can apply.

   The Router Lifetime field in the Router Advertisement messages that
   the mobile access gateway sends on the access link SHOULD be kept to
   low.

   In access networks where SEND [RFC-3971] is not deployed, the mobile
   access gateway can withdraw the previous default-router entry, by
   sending a Router Advertisement using the link-local address that of
   the previous mobile access gateway and with the Router Lifetime field
   set to value zero, then this will force the flush of the previous
   default-router entry from the mobile node's cache, as specified in
   Section 6.3.5 [RFC-4861].  However, this approach requires the
   serving mobile access gateway to learn the link-local address of the
   previous mobile access gateway where the mobile node was handed off.

   There are other solutions possible for this problem, including the
   assignment of a fixed link-local address for all the mobility
   entities in a Proxy Mobile IPv6 domain and where SEND [RFC-3971] is
   not deployed.  In such scenario, the mobile node is not required to
   update the default-router entry.  However, this is an implementation
   choice and has no bearing on the protocol interoperability.
   Implementations are free to adopt the best approach that suits their
   target deployments.

6.9.4.  Retransmissions and Rate Limiting

   The mobile access gateway is responsible for retransmissions and rate
   limiting the binding registration requests that it sends to the local
   mobility anchor.  The Retransmission and the Rate Limiting rules are
   as specified in [RFC-3775].  However, the following considerations
   MUST be applied.


   1.  When the mobile access gateway sends a Proxy Binding Update
       request, it should use the constant, INITIAL_BINDINGACK_TIMEOUT
       [RFC-3775], for configuring the retransmission timer, as
       specified in Section 11.8 [RFC-3775].  However, the mobile access
       gateway is not required to use a longer retransmission interval
       of InitialBindackTimeoutFirstReg as specified in [RFC-3775] for
       the initial binding registration request.




Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 51]

Internet-Draft              Proxy Mobile IPv6              February 2008


   2.  If the mobile access gateway fails to receive a valid matching
       response for a registration or re-registration message within the
       retransmission interval, it SHOULD retransmit the message until a
       response is received.  However, the mobile access gateway MUST
       ensure the mobile node is still attached to the connected link
       before retransmitting the message.

   3.  As specified in Section 11.8 [RFC-3775], the mobile access
       gateway MUST use an exponential back-off process in which the
       timeout period is doubled upon each retransmission, until either
       the node receives a response or the timeout period reaches the
       value MAX_BINDACK_TIMEOUT [RFC-3775].  The mobile access gateway
       MAY continue to send these messages at this slower rate
       indefinitely.

   4.  If Timestamp based scheme is in use, the retransmitted Proxy
       Binding Update messages MUST use the latest timestamp.  If
       Sequence number scheme is in use, the retransmitted Proxy Binding
       Update messages MUST use a Sequence Number value greater than
       that used for the previous transmission of this Proxy Binding
       Update message, just as specified in [RFC-3775].

6.10.  Routing Considerations

   This section describes how the mobile access gateway handles the
   traffic to/from the mobile node that is attached to one of its access
   interface.


                 Proxy-CoA                   LMAA
                    |                          |
    +--+          +---+                      +---+          +--+
    |MN|----------|MAG|======================|LMA|----------|CN|
    +--+          +---+                      +---+          +--+
                            IPv6 Tunnel


                    Figure 12: Proxy Mobile IPv6 Tunnel

6.10.1.  Transport Network

   The transport network between the local mobility anchor and the
   mobile access gateway can be either an IPv6 or IPv4 network.
   However, this specification only deals with the IPv6 transport and
   the companion document [ID-IPV4-PMIP6] specifies the required
   extensions for negotiating IPv4 transport and the corresponding
   encapsulation mode for supporting this protocol operation.




Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 52]

Internet-Draft              Proxy Mobile IPv6              February 2008


6.10.2.  Tunneling & Encapsulation Modes

   The IPv6 address that a mobile node uses from its home network prefix
   is topologically anchored at the local mobility anchor.  For a mobile
   node to use this address from an access network attached to a mobile
   access gateway, proper tunneling techniques have to be in place.
   Tunneling hides the network topology and allows the mobile node's
   IPv6 datagram to be encapsulated as a payload of another IPv6 packet
   and to be routed between the local mobility anchor and the mobile
   access gateway.  The Mobile IPv6 base specification [RFC-3775]
   defines the use of IPv6-over-IPv6 tunneling, between the home agent
   and the mobile node and this specification extends the use of the
   same tunneling mechanism between the local mobility anchor and the
   mobile access gateway.

   On most operating systems, tunnels are implemented as a virtual
   point-to-point interface.  The source and the destination address of
   the two end points of this virtual interface along with the
   encapsulation mode are specified for this virtual interface.  Any
   packet that is routed over this interface gets encapsulated with the
   outer header and the addresses as specified for that point to point
   tunnel interface.  For creating a point to point tunnel to any local
   mobility anchor, the mobile access gateway may implement a tunnel
   interface with the source address field set to its Proxy-CoA address
   and the destination address field set to the LMA address.

   The following are the supported packet encapsulation modes that can
   be used by the mobile access gateway and the local mobility anchor
   for routing mobile node's IPv6 datagrams.

   o  IPv6-In-IPv6 - IPv6 datagram encapsulated in an IPv6 packet [RFC-
      2473].

   o  IPv6-In-IPv4 - IPv6 datagram encapsulation in an IPv4 packet.  The
      details on how this mode is negotiated is specified in [ID-IPV4-
      PMIP6].

   o  IPv6-In-IPv4-UDP - IPv6 datagram encapsulation in an IPv4 UDP
      packet.  This mode is specified in [ID-IPV4-PMIP6].

6.10.3.  Local Routing

   If there is data traffic between a visiting mobile node and a
   correspondent node that is locally attached to an access link
   connected to the mobile access gateway, the mobile access gateway MAY
   optimize on the delivery efforts by locally routing the packets and
   by not reverse tunneling them to the mobile node's local mobility
   anchor.  The configuration variable, EnableMAGLocalRouting MAY be



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 53]

Internet-Draft              Proxy Mobile IPv6              February 2008


   used for controlling this aspect.  However, in some systems, this may
   have an implication on the mobile node's accounting and policy
   enforcement as the local mobility anchor is not in the path for that
   traffic and it will not be able to apply any traffic policies or do
   any accounting for those flows.

   This decision of path optimization SHOULD be based on the policy
   configured on the mobile access gateway, but enforced by the mobile
   node's local mobility anchor.  The specific details on how this is
   achieved are beyond of the scope of this document.

6.10.4.  Tunnel Management

   All the considerations mentioned in Section 5.6.1 for the tunnel
   management on the local mobility anchor apply for the mobile access
   gateway as well.

6.10.5.  Forwarding Rules

   Forwarding Packets sent to the Mobile Node's Home Network:

   o  On receiving a packet from the bi-directional tunnel established
      with the mobile node's local mobility anchor, the mobile access
      gateway MUST use the destination address of the inner packet for
      forwarding it on the interface where the destination network
      prefix is hosted.  The mobile access gateway MUST remove the outer
      header before forwarding the packet.  If the mobile access gateway
      cannot find the connected interface for that destination address,
      it MUST silently drop the packet.  For reporting an error in such
      a scenario, in the form of ICMP control message, the
      considerations from Generic Packet Tunneling specification [RFC-
      2473] must be applied.

   o  On receiving a packet from a correspondent node that is locally
      connected and which is destined to a mobile node that is on
      another locally connected access link, the mobile access gateway
      MUST check the configuration variable, EnableMAGLocalRouting, to
      ensure the mobile access gateway is allowed to route the packet
      directly to the mobile node.  If the mobile access gateway is not
      allowed to route the packet directly, it MUST route the packet
      through the bi-directional tunnel established between itself and
      the mobile node's local mobility anchor.  Otherwise, it can route
      the packet directly to the mobile node.

   Forwarding Packets Sent by the Mobile Node:

   o  On receiving a packet from a mobile node connected to its access
      link, the mobile access gateway MUST ensure that there is an



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 54]

Internet-Draft              Proxy Mobile IPv6              February 2008


      established binding for that mobile node with its local mobility
      anchor before forwarding the packet directly to the destination or
      before tunneling the packet to the mobile node's local mobility
      anchor.

   o  On receiving a packet from a mobile node connected to its access
      link to a destination that is locally connected, the mobile access
      gateway MUST check the configuration variable,
      EnableMAGLocalRouting, to ensure the mobile access gateway is
      allowed to route the packet directly to the destination.  If the
      mobile access gateway is not allowed to route the packet directly,
      it MUST route the packet through the bi-directional tunnel
      established between itself and the mobile node's local mobility
      anchor.  Otherwise, it can route the packet directly to the
      destination.

   o  On receiving a packet from the mobile node connected to its access
      link, to a destination that is not directly connected, the packet
      MUST be forwarded to the local mobility anchor through the bi-
      directional tunnel established between itself and the mobile
      node's local mobility anchor.  However, the packets that are sent
      with the link-local source address MUST NOT be forwarded.  The
      format of the tunneled packet is shown below.  Additionally, when
      using IPv4 transport, the format of the tunneled packet is as
      described in [ID-IPV4-PMIP6].


        IPv6 header (src= Proxy-CoA, dst= LMAA  /* Tunnel Header */
           IPv6 header (src= MN-HoA, dst= CN )  /* Packet Header */
              Upper layer protocols             /* Packet Content*/



                 Figure 13: Tunneled Packets from MAG to LMA

6.11.  Supporting DHCPv6 based Address Configuration on the Access Link

   This section explains how Stateful Address Configuration using DHCPv6
   can be enabled on the access link attached to a mobile access gateway
   and how a mobile node attached to that link can obtain an address
   from its home network prefix using DHCPv6.

   o  For supporting Stateful Address Configuration using DHCPv6, the
      DHCPv6 relay agent [RFC-3315] service MUST be enabled on each of
      the access links in the Proxy Mobile IPv6 domain.  Further, as
      specified in Section 20 [RFC-3315], the relay agent should be
      configured to use a list of destination addresses, which MAY
      include unicast addresses, the All_DHCP_Servers multicast address,



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 55]

Internet-Draft              Proxy Mobile IPv6              February 2008


      or other addresses selected by the network administrator.

   o  The DHCPv6 server in the Proxy Mobile IPv6 domain can be
      configured with a list of prefix pools (P1, P2, ..., Pn).  Each
      one of these prefix pools corresponds to a home network prefix
      that a local mobility anchor allocates to a mobile node in that
      domain.  However, the DHCPv6 server will not know the relation
      between a given address pool and a mobile node to which the
      corresponding prefix is allocated.  It just views these pools as
      prefixes hosted on different links in that domain.

   o  When a mobile node sends a DHCPv6 request message, the DHCP relay
      agent function on the access link will set the link-address field
      in the DHCP message to an address in the mobile node's home
      network prefix, so as to provide a prefix hint to the DHCP Server
      for the address pool selection.  The DHCP server on receiving the
      request from the mobile node, will allocate an address from the
      prefix pool present in the link-address field of the request.

   o  Once the mobile node obtains an address and moves to a different
      link and sends a DHCP request, the DHCP relay agent on the new
      link will set the prefix hint in the DHCP messages to the mobile
      node's home network prefix.  The DHCP server will identify the
      client from the Client-DUID option and present in the request and
      will allocate the same address as before.

   o  The DHCP based address configuration is not recommended for
      deployments where the local mobility anchor and the mobile access
      gateways are located in different administrative domains.  For
      this configuration to work, all the mobile access gateways in the
      Proxy Mobile IPv6 domain should be able to ensure that the DHCP
      requests from a given mobile node anchored on any of the access
      links in that domain, will always be handled by the same DHCP
      server.

   o  The DHCP server should be configured to offer low address lease
      times.  A lease time that is too large prevents the DHCP server
      from reclaiming the address even after the local mobility anchor
      deletes the mobile node's binding cache entry.

6.12.  Home Network Prefix Renumbering

   If the mobile node's home network prefix gets renumbered or becomes
   invalid during the middle of a mobility session, the mobile access
   gateway MUST withdraw the prefix by sending a Router Advertisement on
   the access link with zero prefix lifetime for the mobile node's home
   network prefix.  Also, the local mobility anchor and the mobile
   access gateway MUST delete the routing state for that prefix.



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 56]

Internet-Draft              Proxy Mobile IPv6              February 2008


   However, the specific details on how the local mobility anchor
   notifies the mobile access gateway about the mobile node's home
   network prefix renumbering are outside the scope of this document.

6.13.  Mobile Node Detachment Detection and Resource Cleanup

   Before sending a Proxy Binding Update message to the local mobility
   anchor for extending the lifetime of a currently existing binding of
   a mobile node, the mobile access gateway MUST make sure the mobile
   node is still attached to the connected link by using some reliable
   method.  If the mobile access gateway cannot predictably detect the
   presence of the mobile node on the connected link, it MUST NOT
   attempt to extend the registration lifetime of the mobile node.
   Further, in such scenario, the mobile access gateway SHOULD terminate
   the binding of the mobile node by sending a Proxy Binding Update
   message to the mobile node's local mobility anchor with lifetime
   value set to 0.  It MUST also remove any local state such as the
   Binding Update List entry created for that mobile node.

   The specific detection mechanism of the loss of a visiting mobile
   node on the connected link is specific to the access link between the
   mobile node and the mobile access gateway and is outside the scope of
   this document.  Typically, there are various link-layer specific
   events specific to each access technology that the mobile access
   gateway can depend on for detecting the node loss.  In general, the
   mobile access gateway can depend on one or more of the following
   methods for the detection presence of the mobile node on the
   connected link:

   o  Link-layer event specific to the access technology

   o  PPP Session termination event on point-to-point link types

   o  IPv6 Neighbor Unreachability Detection event from IPv6 stack

   o  Notification event from the local mobility anchor

6.14.  Allowing network access to other IPv6 nodes

   In some Proxy Mobile IPv6 deployments, network operators may want to
   provision the mobile access gateway to offer network-based mobility
   management service only to some visiting mobile nodes and enable just
   regular IP access to some other nodes.  This requires the network to
   have control on when to enable network-based mobility management
   service to a mobile node and when to enable regular IPv6 access.
   This specification does not disallow such configuration.

   Upon detecting a mobile node on its access link and after policy



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 57]

Internet-Draft              Proxy Mobile IPv6              February 2008


   considerations, the mobile access gateway MUST determine if network-
   based mobility management service should be offered to that mobile
   node.  If the mobile node is entitled for network-based mobility
   management service, then the mobile access gateway must ensure the
   mobile node believes it is on its home link, as explained in various
   sections of this specification.

   If the mobile node is not entitled for the network-based mobility
   management service, as determined from the policy considerations, the
   mobile access gateway MAY choose to offer regular IPv6 access to the
   mobile node and in such scenario the normal IPv6 considerations
   apply.  If IPv6 access is enabled, the mobile node SHOULD be able to
   obtain an IPv6 address using normal IPv6 address configuration
   procedures.  The obtained address must be from a local visitor
   network prefix.  This essentially ensures that the mobile access
   gateway functions as a normal access router to a mobile node attached
   to its access link and with out impacting its host-based mobility
   protocol operation.


7.  Mobile Node Operation

   This non-normative section explains the mobile node's operation in a
   Proxy Mobile IPv6 domain.

7.1.  Moving into a Proxy Mobile IPv6 Domain

   When a mobile node enters a Proxy Mobile IPv6 domain and attaches to
   an access network, the mobile access gateway on the access link
   detects the attachment of the mobile node and completes the binding
   registration with the mobile node's local mobility anchor.  If the
   binding update operation is successfully performed, the mobile access
   gateway will create the required state and setup the data path for
   the mobile node's data traffic.

   If the mobile node is IPv6 enabled, on attaching to the access link,
   it will typically send Router Solicitation message [RFC-4861].  The
   mobile access gateway on the access link will respond to the Router
   Solicitation message with a Router Advertisement.  The Router
   Advertisement will have the mobile node's home network prefix,
   default-router address and other address configuration parameters.

   If the mobile access gateway on the access link, receives a Router
   Solicitation message from the mobile node, before it completed the
   signaling with the mobile node's local mobility anchor, the mobile
   access gateway may not know the mobile node's home network prefix and
   may not be able to emulate the mobile node's home link on the access
   link.  In such scenario, the mobile node may notice a slight delay



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 58]

Internet-Draft              Proxy Mobile IPv6              February 2008


   before it receives a Router Advertisement message.

   If the received Router Advertisement has the Managed Address
   Configuration flag set, the mobile node, as it would normally do,
   will send a DHCPv6 Request [RFC-3315].  The DHCP relay service
   enabled on that access link will ensure the mobile node will obtain
   its IPv6 address as a lease from its home network prefix.

   If the received Router Advertisement does not have the Managed
   Address Configuration flag set and if the mobile node is allowed to
   use an autoconfigured address, the mobile node will be able to obtain
   an IPv6 address using an interface identifier generated as per the
   Autoconf specification [RFC-4862] or as per the Privacy Extensions
   specification [RFC-4941].

   If the mobile node is IPv4 enabled and if the network permits, it
   will be able to obtain the IPv4 address configuration as specified in
   the companion document [ID-IPV4-PMIP6].

   Once the address configuration is complete, the mobile node can
   continue to use this address configuration as long as it is attached
   to the network that is in the scope of that Proxy Mobile IPv6 domain.

7.2.  Roaming in the Proxy Mobile IPv6 Domain

   After obtaining the address configuration in the Proxy Mobile IPv6
   domain, as the mobile node moves and changes its point of attachment
   from one mobile access gateway to the other, it can still continue to
   use the same address configuration.  As long as the attached access
   network is in the scope of that Proxy Mobile IPv6 domain, the mobile
   node will always detect the same link, where it obtained its initial
   address configuration.  If the mobile node performs DHCP operation,
   it will always obtain the same address as before.

   However, the mobile node will always detect a new default-router on
   each connected link, but still advertising the mobile node's home
   network prefix as the on-link prefix and with the other configuration
   parameters consistent with its home link properties.


8.  Message Formats

   This section defines extensions to the Mobile IPv6 [RFC-3775]
   protocol messages.







Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 59]

Internet-Draft              Proxy Mobile IPv6              February 2008


8.1.  Proxy Binding Update Message



       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
                                      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                      |            Sequence #         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |A|H|L|K|M|R|P|  Reserved       |            Lifetime           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      .                                                               .
      .                        Mobility options                       .
      .                                                               .

      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




   A Binding Update message that is sent by a mobile access gateway to a
   local mobility anchor is referred to as the "Proxy Binding Update"
   message.  A new flag (P) is included in the Binding Update message.
   The rest of the Binding Update message format remains the same as
   defined in [RFC-3775] and with the additional (R) and (M) flags as
   specified in [RFC-3963] and [RFC-4140] respectively.


   Proxy Registration Flag (P)

      A new flag (P) is included in the Binding Update message to
      indicate to the local mobility anchor that the Binding Update
      message is a proxy registration.  The flag MUST be set to the
      value of 1 for proxy registrations and MUST be set to 0 for direct
      registrations sent by a mobile node.

   Mobility Options

      Variable-length field of such length that the complete Mobility
      Header is an integer multiple of 8 octets long.  This field
      contains zero or more TLV-encoded mobility options.  The encoding
      and format of defined options are described in Section 6.2 [RFC-
      3775].  The local mobility anchor MUST ignore and skip any options
      which it does not understand.





Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 60]

Internet-Draft              Proxy Mobile IPv6              February 2008


      As per this specification, the following mobility options are
      valid in a Proxy Binding Update message:

         Mobile Node Identifier option

         Home Network Prefix option

         Handoff Indicator option

         Access Technology Type option

         Timestamp option

         Mobile Node Interface Identifier option

         Link-local Address option

   For descriptions of other fields present in this message, refer to
   section 6.1.7 [RFC-3775].


8.2.  Proxy Binding Acknowledgement Message



       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
                                      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                      |   Status      |K|R|P|Reserved |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Sequence #            |           Lifetime            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      .                                                               .
      .                        Mobility options                       .
      .                                                               .
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



   A Binding Acknowledgement message that is sent by a local mobility
   anchor to a mobile access gateway is referred to as the "Proxy
   Binding Acknowledgement" message.  A new flag (P) is included in the
   Binding Acknowledgement message.  The rest of the Binding
   Acknowledgement message format remains the same as defined in [RFC-
   3775] and with the additional (R) and (M) flags as specified in [RFC-
   3963] and [RFC-4140] respectively.



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 61]

Internet-Draft              Proxy Mobile IPv6              February 2008


   Proxy Registration Flag (P)

      A new flag (P) is included in the Binding Acknowledgement message
      to indicate that the local mobility anchor that processed the
      corresponding Proxy Binding Update message supports proxy
      registrations.  The flag is set only if the corresponding Proxy
      Binding Update had the Proxy Registration Flag (P) set to value of
      1.

   Mobility Options

      Variable-length field of such length that the complete Mobility
      Header is an integer multiple of 8 octets long.  This field
      contains zero or more TLV-encoded mobility options.  The encoding
      and format of defined options are described in Section 6.2 [RFC-
      3775].  The mobile access gateway MUST ignore and skip any options
      which it does not understand.

      As per this specification, the following mobility options are
      valid in a Proxy Binding Acknowledgement message:

         Mobile Node Identifier option

         Home Network Prefix option

         Handoff Indicator option

         Access Technology Type option

         Timestamp option

         Mobile Node Interface Identifier option

         Link-local Address option

   Status

      8-bit unsigned integer indicating the disposition of the Proxy
      Binding Update.  Values of the Status field less than 128 indicate
      that the Proxy Binding Update was accepted by the local mobility
      anchor.  Values greater than or equal to 128 indicate that the
      binding registration was rejected by the local mobility anchor.
      Section 8.9 defines the Status values that can used in Proxy
      Binding Acknowledgement message.

   For descriptions of other fields present in this message, refer to
   the section 6.1.8 [RFC-3775].




Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 62]

Internet-Draft              Proxy Mobile IPv6              February 2008


8.3.  Home Network Prefix Option

   A new option, Home Network Prefix Option is defined for using it in
   the Proxy Binding Update and Proxy Binding Acknowledgement messages
   exchanged between a local mobility anchor and a mobile access
   gateway.  This option is used for exchanging the mobile node's home
   network prefix information.

   The Home Network Prefix Option has an alignment requirement of 8n+4.
   Its format is as follows:









































Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 63]

Internet-Draft              Proxy Mobile IPv6              February 2008


       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      |   Reserved    | Prefix Length |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                                                               +
      |                                                               |
      +                    Home Network Prefix                        +
      |                                                               |
      +                                                               +
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Type
           <IANA>

       Length

           8-bit unsigned integer indicating the length of the option
           in octets, excluding the type and length fields. This field
           MUST be set to 18.

       Reserved (R)

           This 8-bit field is unused for now.  The value MUST be
           initialized to 0 by the sender and MUST be ignored by the
           receiver.

       Prefix Length

           8-bit unsigned integer indicating the prefix length of the
           IPv6 prefix contained in the option.

       Home Network Prefix

           A sixteen-byte field containing the mobile node's IPv6 Home
           Network Prefix.


8.4.  Handoff Indicator Option

   A new option, Handoff Indicator Option is defined for using it in the
   Proxy Binding Update and Proxy Binding Acknowledgement messages
   exchanged between a local mobility anchor and a mobile access
   gateway.  This option is used for exchanging the mobile node's
   handoff related hints.




Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 64]

Internet-Draft              Proxy Mobile IPv6              February 2008


   The Handoff Indicator Option has no alignment requirement.  Its
   format 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      |  Reserved (R) |       HI      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


    Type
        <IANA>

    Length

        8-bit unsigned integer indicating the length of the option
        in octets, excluding the type and length fields. This field
        MUST be set to 2.

    Reserved (R)

        This 8-bit field is unused for now.  The value MUST be
        initialized to 0 by the sender and MUST be ignored by the
        receiver.

    Handoff Indicator (HI)

        A 8-bit field that specifies the type of handoff. The values
        (0 - 255) will be allocated and managed by IANA. The following
        values are currently reserved.

        0: Reserved
        1: Attachment over a new interface
        2: Handoff between two different interfaces of the mobile node
        3: Handoff between mobile access gateways for the same interface
        4: Handoff state unknown
        5: Handoff state not changed (Re-registration)


8.5.  Access Technology Type Option

   A new option, Access Technology Type Option is defined for using it
   in the Proxy Binding Update and Proxy Binding Acknowledgement
   messages exchanged between a local mobility anchor and a mobile
   access gateway.  This option is used for exchanging the type of the
   access technology using which the mobile node is currently attached



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 65]

Internet-Draft              Proxy Mobile IPv6              February 2008


   to the mobile access gateway.

   The Access Technology Type Option has no alignment requirement.  Its
   format 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      |  Reserved (R) |      ATT      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Type
         <IANA>

     Length

         8-bit unsigned integer indicating the length of the option
         in octets, excluding the type and length fields. This field
         MUST be set to 2.

     Reserved (R)

         This 8-bit field is unused for now.  The value MUST be
         initialized to 0 by the sender and MUST be ignored by the
         receiver.

     Access Technology Type (ATT)

         A 8-bit field that specifies the access technology through
         which the mobile node is connected to the access link on the
         mobile access gateway.

         The values (0 - 255) will be allocated and managed by IANA. The
         following values are currently reserved for the below specified
         access technology types.

         0: Reserved
         1: Virtual
         2: PPP
         3: 802.3 (Ethernet)
         4: 802.11a/b/g
         5: 802.16e







Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 66]

Internet-Draft              Proxy Mobile IPv6              February 2008


8.6.  Mobile Node Interface Identifier Option

   A new option, Mobile Node Interface Identifier Option is defined for
   using it in the Proxy Binding Update and Proxy Binding
   Acknowledgement messages exchanged between a local mobility anchor
   and a mobile access gateway.  This option is used for exchanging the
   mobile node's interface identifier.

   The format of the Interface Identifier option when the interface
   identifier is 8 bytes is shown below.  When the size is different,
   the option MUST be aligned appropriately, as per mobility option
   alignment requirements specified in [RFC-3775].




     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     |          Reserved             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    +                     Interface Identifier                      +
    .                              ...                              .
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Type
         <IANA>

     Length
         8-bit unsigned integer indicating the length of the option
         in octets, excluding the type and length fields.

     Reserved

         This field is unused for now.  The value MUST be initialized to
         0 by the sender and MUST be ignored by the receiver.

     Interface Identifier

         A variable length field containing the mobile node's interface
         identifier.

         The content and format of this field (including byte and bit
         ordering) is as specified in Section 4.6 [RFC-4861] for
         carrying Link-Layer Address.




Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 67]

Internet-Draft              Proxy Mobile IPv6              February 2008


8.7.  Link-local Address Option

   A new option, Link-local Address Option is defined for using it in
   the Proxy Binding Update and Proxy Binding Acknowledgement messages
   exchanged between a local mobility anchor and a mobile access
   gateway.  This option is used for exchanging the mobile node's link-
   local address.

   The Link-local Address option has an alignment requirement of 8n+6.
   Its format 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     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                                                               +
      |                                                               |
      +                  Link-local Address                           +
      |                                                               |
      +                                                               +
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Type
           <IANA>

       Length

           8-bit unsigned integer indicating the length of the option
           in octets, excluding the type and length fields. This field
           MUST be set to 16.

       Link-local Address

           A sixteen-byte field containing the mobile node's link-local
           address.


8.8.  Timestamp Option

   A new option, Timestamp Option is defined for use in the Proxy
   Binding Update and Proxy Binding Acknowledgement messages.




Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 68]

Internet-Draft              Proxy Mobile IPv6              February 2008


   The Timestamp option has an alignment requirement of 8n+2.  Its
   format 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      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                          Timestamp                            +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    Type
        <IANA>

    Length

        8-bit unsigned integer indicating the length in octets of
        the option, excluding the type and length fields.  The value
        for this field MUST be set to 8.

    Timestamp

      A 64-bit unsigned integer field containing a timestamp.  The value
      indicates the number of seconds since January 1, 1970, 00:00 UTC,
      by using a fixed point format.  In this format, the integer number
      of seconds is contained in the first 48 bits of the field, and the
      remaining 16 bits indicate the number of 1/65536 fractions of a
      second.


8.9.  Status Values

   This document defines the following new Status values for use in
   Proxy Binding Acknowledgement message.  These values are to be
   allocated from the same number space, as defined in Section 6.1.8
   [RFC-3775].

   Status values less than 128 indicate that the Proxy Binding Update
   request was accepted by the local mobility anchor.  Status values
   greater than 128 indicate that the Proxy Binding Update was rejected
   by the local mobility anchor.





Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 69]

Internet-Draft              Proxy Mobile IPv6              February 2008


   PROXY_REG_NOT_ENABLED:

      Proxy registration not enabled for the mobile node


   NOT_LMA_FOR_THIS_MOBILE_NODE:

      Not local mobility anchor for this mobile node


   MAG_NOT_AUTHORIZED_FOR_PROXY_REG:

      The mobile access gateway is not authorized to send proxy binding
      registrations


   NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX

      The mobile node is not authorized for the requesting home network
      prefix


   TIMESTAMP_MISMATCH:

      Invalid timestamp value (the clocks are out of sync)


   TIMESTAMP_LOWER_THAN_PREV_ACCEPTED:

      The timestamp value is lower than the previously accepted value


   MISSING_HOME_NETWORK_PREFIX_OPTION

      Missing home network prefix option


   MISSING_MN_IDENTIFIER_OPTION:

      Missing mobile node identifier option


   MISSING_HANDOFF_INDICATOR_OPTION

      Missing handoff indicator option


   MISSING_ACCESS_TECH_TYPE_OPTION



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 70]

Internet-Draft              Proxy Mobile IPv6              February 2008


      Missing access technology type option


   Additionally, the following Status values defined in [RFC-3775] can
   also be used in Proxy Binding Acknowledgement message.

      0 Proxy Binding Update accepted

      128 Reason unspecified

      129 Administratively prohibited

      130 Insufficient resources


9.  Protocol Configuration Variables

   The local mobility anchor MUST allow the following variables to be
   configured by the system management.


   MinDelayBeforeBCEDelete

      This variable specifies the amount of time in milliseconds the
      local mobility anchor MUST wait before it deletes a Binding Cache
      entry of a mobile node, upon receiving a Proxy Binding Update
      message from a mobile access gateway with a lifetime value of 0.
      During this wait time, if the local mobility anchor receives a
      Proxy Binding Update for the same mobility binding, with lifetime
      value greater than 0, then it must update the binding cache entry
      with the accepted binding values.  By the end of this wait-time,
      if the local mobility anchor did not receive any valid Proxy
      Binding Update message for that mobility binding, it MUST delete
      the Binding Cache entry.  This delay essentially ensures a mobile
      node's Binding Cache entry is not deleted too quickly and allows
      some time for the new mobile access gateway to complete the
      signaling for the mobile node.

      The default value for this variable is 10000 milliseconds.

   MaxDelayBeforeNewBCEAssign

      This variable specifies the amount of time in milliseconds the
      local mobility anchor MUST wait for the de-registration message
      for an existing mobility session before it decides to create a new
      mobility session.





Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 71]

Internet-Draft              Proxy Mobile IPv6              February 2008


      The default value for this variable is 500 milliseconds.

   TimestampValidityWindow

      This variable specifies the maximum amount of time difference in
      milliseconds between the timestamp in the received Proxy Binding
      Update message and the current time-of-day on the local mobility
      anchor, that is allowed by the local mobility anchor for the
      received message to be considered valid.

      The default value for this variable is 300 milliseconds.  This
      variable MUST be adjusted to suit the deployments.


   The mobile access gateway MUST allow the following variables to be
   configured by the system management.


   EnableMAGLocalrouting

      This flag indicates whether or not the mobile access gateway is
      allowed to enable local routing of the traffic exchanged between a
      visiting mobile node and a correspondent node that is locally
      connected to one of the interfaces of the mobile access gateway.
      The correspondent node can be another visiting mobile node as
      well, or a local fixed node.

      The default value for this flag is set to "FALSE", indicating that
      the mobile access gateway MUST reverse tunnel all the traffic to
      the mobile node's local mobility anchor.

      When the value of this flag is set to "TRUE", the mobile access
      gateway MUST route the traffic locally.

      This aspect of local routing MAY be defined as policy on a per
      mobile basis and when present will take precedence over this flag.


10.  IANA Considerations

   This document defines six new Mobility Header options, the Home
   Network Prefix option, Handoff Indicator option, Access Technology
   Type option, Interface Identifier option, Link-local Address option
   and Timestamp option.  These options are described in Section 8.  The
   Type value for these options needs to be assigned from the same
   numbering space as allocated for the other mobility options, as
   defined in [RFC-3775].




Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 72]

Internet-Draft              Proxy Mobile IPv6              February 2008


   The Access Technology Type option defined in Section 8.5 of this
   document introduces a new Access Technology type numbering space,
   where the values from 0 to 5 have been reserved by this document.
   Approval of new Access Technology type numbers are to be made through
   IANA Expert Review.

   This document also defines new Binding Acknowledgement status values
   as described in Section 8.9.  The status values MUST be assigned from
   the same number space used for Binding Acknowledgement status values,
   as defined in [RFC-3775].  The allocated values for each of these
   status values MUST be greater than 128.


11.  Security Considerations

   The potential security threats against any network-based mobility
   management protocol are described in [RFC-4832].  This section
   explains how Proxy Mobile IPv6 protocol defends itself against those
   threats.

   Proxy Mobile IPv6 protocol requires the signaling messages, Proxy
   Binding Update and Proxy Binding Acknowledgement, exchanged between
   the mobile access gateway and the local mobility anchor to be
   protected using IPsec, using the established security association
   between them.  This essentially eliminates the threats related to the
   impersonation of the mobile access gateway or the local mobility
   anchor.

   This specification allows a mobile access gateway to send binding
   registration messages on behalf of a mobile node.  If proper
   authorization checks are not in place, a malicious node may be able
   to hijack a mobile node's session or may carry out a denial-of-
   service attack.  To prevent this attack, this specification requires
   the local mobility anchor to allow only authorized mobile access
   gateways that are part of that Proxy Mobile IPv6 domain to send
   binding registration messages on behalf of a mobile node.

   To eliminate the threats on the interface between the mobile access
   gateway and the mobile node, this specification requires an
   established trust between the mobile access gateway and the mobile
   node and to authenticate and authorize the mobile node before it is
   allowed to access the network.  Further, the established
   authentication mechanisms enabled on that access link will ensure
   that there is a secure binding between the mobile node's identity and
   its link-layer address.  The mobile access gateway will definitively
   identify the mobile node from the packets that it receives on that
   access link.




Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 73]

Internet-Draft              Proxy Mobile IPv6              February 2008


   To address the threat related to a compromised mobile access gateway,
   the local mobility anchor, before accepting a Proxy Binding Update
   message for a given mobile node, may ensure that the mobile node is
   definitively attached to the mobile access gateway that sent the
   proxy binding registration request.  This may be accomplished by
   contacting a trusted entity which is able to track the mobile node's
   current point of attachment.  However, the specific details of the
   actual mechanisms for achieving this is outside the scope of this
   document.


12.  Acknowledgements

   The authors would like to specially thank Julien Laganier, Christian
   Vogt, Pete McCann, Brian Haley, Ahmad Muhanna, JinHyeock Choi for
   their thorough review of this document.

   The authors would also like to thank Alex Petrescu, Alice Qinxia,
   Alper Yegin, Ashutosh Dutta, Behcet Sarikaya, Fred Templin, Genadi
   Velev, George Tsirtsis, Gerardo Giaretta, Henrik Levkowetz, Hesham
   Soliman, James Kempf, Jari Arkko, Jean-Michel Combes, John Zhao,
   Jong-Hyouk Lee, Jonne Soininen, Jouni Korhonen, Kalin Getov, Kilian
   Weniger, Marco Liebsch, Mohamed Khalil, Nishida Katsutoshi, Phil
   Roberts, Ryuji Wakikawa, Sangjin Jeong, Suresh Krishnan, Ved Kafle,
   Vidya Narayanan, Youn-Hee Han and many others for their passionate
   discussions in the working group mailing list on the topic of
   localized mobility management solutions.  These discussions
   stimulated much of the thinking and shaped the draft to the current
   form.  We acknowledge that !

   The authors would also like to thank Ole Troan, Akiko Hattori, Parviz
   Yegani, Mark Grayson, Michael Hammer, Vojislav Vucetic, Jay Iyer and
   Tim Stammers for their input on this document.


13.  References

13.1.  Normative References

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

   [RFC-2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
   IPv6 Specification", RFC 2473, December 1998.

   [RFC-3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and
   M.Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
   RFC 3315, July 2003.



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 74]

Internet-Draft              Proxy Mobile IPv6              February 2008


   [RFC-3775] Johnson, D., Perkins, C., Arkko, J., "Mobility Support in
   IPv6", RFC 3775, June 2004.

   [RFC-3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
   Thubert, "Network Mobility (NEMO) Basic Support Protocol", RFC 3963,
   January 2005.

   [RFC-4283] Patel, A., Leung, K., Khalil, M., Akhtar, H., and K.
   Chowdhury, "Mobile Node Identifier Option for Mobile IPv6", RFC 4283,
   November 2005.

   [RFC-4301] Kent, S. and Atkinson, R., "Security Architecture for the
   Internet Protocol", RFC 4301, December 2005.

   [RFC-4303] Kent, S. "IP Encapsulating Security Protocol (ESP)", RFC
   4303, December 2005.

   [RFC-4861] Narten, T., Nordmark, E. and W. Simpson, Soliman, H.,
   "Neighbor Discovery for IP Version 6 (IPv6)", RFC 4861, September
   2007.

13.2.  Informative References

   [RFC-1661] Simpson, W., Ed., "The Point-To-Point Protocol (PPP)", STD
   51, RFC 1661, July 1994.

   [RFC-3971] Arkko, J., Ed., Kempf, J., Sommerfeld, B., Zill, B., and
   P. Nikander, "SEcure Neighbor Discovery (SEND)", RFC 3971, March
   2005.

   [RFC-4140] Soliman, H., Castelluccia, C., El Malki, K., and L.
   Bellier, "Hierarchical Mobile IPv6 Mobility Management (HMIPv6)", RFC
   4140, August 2005.

   [RFC-4306] Kaufman, C, et al, "Internet Key Exchange (IKEv2)
   Protocol", RFC 4306, December 2005.

   [RFC-4330] Mills, D., "Simple Network Time Protocol (SNTP) Version 4
   for IPv4, IPv6 and OSI", RFC 2030, October 1996.

   [RFC-4372] Adrangi, F., Lior, A., Korhonen, J., and J. Loughney,
   "Chargeable User Identity", RFC 4372, January 2006.

   [RFC-4830] Kempf, J., Leung, K., Roberts, P., Nishida, K., Giaretta,
   G., Liebsch, M., "Problem Statement for Network-based Localized
   Mobility Management", September 2006.

   [RFC-4831] Kempf, J., Leung, K., Roberts, P., Nishida, K., Giaretta,



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 75]

Internet-Draft              Proxy Mobile IPv6              February 2008


   G., Liebsch, M., "Goals for Network-based Localized Mobility
   Management", October 2006.

   [RFC-4832] Vogt, C., Kempf, J., "Security Threats to Network-Based
   Localized Mobility Management", September 2006.

   [RFC-4862] Thompson, S., Narten, T., Jinmei, T., "IPv6 Stateless
   Address Autoconfiguration", RFC 4862, September 2007.

   [RFC-4941] Narten, T., Draves, R., Krishnan, S., "Privacy Extensions
   for Stateless Address Autoconfiguration in IPv6", RFC 4941, September
   2007.

   [ID-IPV4-PMIP6] Wakikawa, R. and Gundavelli, S., "IPv4 Support for
   Proxy Mobile IPv6", draft-ietf-netlmm-pmip6-ipv4-support-02.txt,
   November 2007.

   [ID-DNAV6] Kempf, J., et al "Detecting Network Attachment in IPv6
   Networks (DNAv6)", draft-ietf-dna-protocol-06.txt, October 2006.


Appendix A.  Proxy Mobile IPv6 interactions with AAA Infrastructure


   Every mobile node that roams in a proxy Mobile IPv6 domain, would
   typically be identified by an identifier, MN-Identifier, and that
   identifier will have an associated policy profile that identifies the
   mobile node's home network prefix, permitted address configuration
   modes, roaming policy and other parameters that are essential for
   providing network-based mobility service.  This information is
   typically configured in AAA.  It is possible the home network prefix
   is dynamically allocated for the mobile node when it boots up for the
   first time in the network, or it could be a statically configured
   value on per mobile node basis.  However, for all practical purposes,
   the network entities in the proxy Mobile IPv6 domain, while serving a
   mobile node will have access to this profile and these entities can
   query this information using RADIUS/DIAMETER protocols.



Appendix B.  Supporting Shared-Prefix Model using DHCPv6


   This specification supports Per-MN-Prefix model.  However, it is
   possible to support Shared-Prefix model under the following
   guidelines.

   The mobile node is allowed to use stateful address configuration



Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 76]

Internet-Draft              Proxy Mobile IPv6              February 2008


   using DHCPv6 for obtaining its address configuration.  The mobile
   node is not allowed to use any of the stateless autoconfiguration
   techniques.  The permitted address configuration models for the
   mobile node on the access link can be enforced by the mobile access
   gateway, by setting the relevant flags in the Router Advertisements,
   as per [RFC-4861].

   The Home Network Prefix option that is sent by the mobile access
   gateway in the Proxy Binding Update message, must contain the 128-bit
   host address that the mobile node obtained via DHCPv6.

   Routing state at the mobile access gateway:

   For all IPv6 traffic from the source MN-HoA::/128 to
   _ANY_DESTINATION_, route via tunnel0, next-hop LMAA, where tunnel0 is
   the MAG to LMA tunnel.

   Routing state at the local mobility anchor:

   For all IPv6 traffic to destination MN-HoA::/128, route via tunnel0,
   next-hop Proxy-CoA, where tunnel0 is the LMA to MAG tunnel.



Appendix C.  Routing State

   The following section explains the routing state for a mobile node on
   the mobile access gateway.  This routing state reflects only one
   specific way of implementation and one MAY choose to implement it in
   other ways.  The policy based route defined below acts as a traffic
   selection rule for routing a mobile node's traffic through a specific
   tunnel created between the mobile access gateway and that mobile
   node's local mobility anchor and with the specific encapsulation
   mode, as negotiated.

   The below example identifies the routing state for two visiting
   mobile nodes, MN1 and MN2 with their respective local mobility
   anchors LMA1 and LMA2.

   For all traffic from the mobile node, identified by the mobile node's
   MAC address, ingress interface or source prefix (MN-HNP) to
   _ANY_DESTINATION_ route via interface tunnel0, next-hop LMAA.









Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 77]

Internet-Draft              Proxy Mobile IPv6              February 2008


   +==================================================================+
   |  Packet Source    | Destination Address  | Destination Interface |
   +==================================================================+
   | MAC_Address_MN1,  | _ANY_DESTINATION_    |     Tunnel0           |
   | (IPv6 Prefix or   |----------------------------------------------|
   |  Input Interface) | Locally Connected    |     Tunnel0           |
   +------------------------------------------------------------------+
   | MAC_Address_MN2,  | _ANY_DESTINATION_    |     Tunnel1           |
   + (IPv6 Prefix or   -----------------------------------------------|
   |  Input Interface  | Locally Connected    |     direct            |
   +------------------------------------------------------------------+


               Figure 22: Example - Policy based Route Table



   +==================================================================+
   | Interface | Source Address | Destination Address | Encapsulation |
   +==================================================================+
   | Tunnel0   |   Proxy-CoA    |        LMAA1         | IPv6-in-IPv6 |
   +------------------------------------------------------------------+
   | Tunnel1   |IPv4-Proxy-CoA  |    IPv4-LMA2         | IPv6-in-IPv4 |
   +------------------------------------------------------------------+


                Figure 23: Example - Tunnel Interface Table


Authors' Addresses

   Sri Gundavelli
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134
   USA

   Email: sgundave@cisco.com


   Kent Leung
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134
   USA

   Email: kleung@cisco.com




Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 78]

Internet-Draft              Proxy Mobile IPv6              February 2008


   Vijay Devarapalli
   Azaire Networks
   4800 Great America Pkwy
   Santa Clara, CA  95054
   USA

   Email: vijay.devarapalli@azairenet.com


   Kuntal Chowdhury
   Starent Networks
   30 International Place
   Tewksbury, MA


   Email: kchowdhury@starentnetworks.com


   Basavaraj Patil
   Nokia Siemens Networks
   6000 Connection Drive
   Irving, TX  75039
   USA

   Email: basavaraj.patil@nsn.com


























Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 79]

Internet-Draft              Proxy Mobile IPv6              February 2008


Full Copyright Statement

   Copyright (C) The IETF Trust (2008).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.


Acknowledgment

   Funding for the RFC Editor function is provided by the IETF
   Administrative Support Activity (IASA).





Gundavelli (Editor), et al.  Expires August 12, 2008           [Page 80]


Html markup produced by rfcmarkup 1.107, available from http://tools.ietf.org/tools/rfcmarkup/