GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc5213

Network Working Group S. Gundavelli, Ed. Request for Comments: 5213 K. Leung Category: Standards Track Cisco

                                                        V. Devarapalli
                                                              Wichorus
                                                          K. Chowdhury
                                                      Starent Networks
                                                              B. Patil
                                                                 Nokia
                                                           August 2008
                         Proxy Mobile IPv6

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Abstract

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

Gundavelli, et al. Standards Track [Page 1] RFC 5213 Proxy Mobile IPv6 August 2008

Table of Contents

 1.  Introduction .................................................  4
 2.  Conventions and Terminology  .................................  5
   2.1.  Conventions Used in This Document  .......................  5
   2.2.  Terminology  .............................................  5
 3.  Proxy Mobile IPv6 Protocol Overview  .........................  9
 4.  Proxy Mobile IPv6 Protocol Security  ......................... 15
   4.1.  Peer Authorization Database (PAD) Example Entries  ....... 16
   4.2.  Security Policy Database (SPD) Example Entries ........... 17
 5.  Local Mobility Anchor Operation  ............................. 17
   5.1.  Extensions to Binding Cache Entry Data Structure ......... 18
   5.2.  Supported Home Network Prefix Models ..................... 19
   5.3.  Signaling Considerations ................................. 20
     5.3.1.  Processing Proxy Binding Updates ..................... 20
     5.3.2.  Initial Binding Registration (New Mobility Session) .. 22
     5.3.3.  Binding Lifetime Extension (No Handoff)  ............. 23
     5.3.4.  Binding Lifetime Extension (After Handoff) ........... 24
     5.3.5.  Binding De-Registration  ............................. 24
     5.3.6.  Constructing the Proxy Binding Acknowledgement
             Message  ............................................. 25
   5.4.  Multihoming Support  ..................................... 27
     5.4.1.  Binding Cache Entry Lookup Considerations  ........... 28
   5.5.  Timestamp Option for Message Ordering  ................... 34
   5.6.  Routing Considerations ................................... 37
     5.6.1.  Bi-Directional Tunnel Management ..................... 37
     5.6.2.  Forwarding Considerations  ........................... 38
     5.6.3.  Explicit Congestion Notification (ECN)
             Considerations for Proxy Mobile IPv6 Tunnels ......... 39
   5.7.  Local Mobility Anchor Address Discovery  ................. 40
   5.8.  Mobile Prefix Discovery Considerations ................... 40
   5.9.  Route Optimization Considerations  ....................... 41
 6.  Mobile Access Gateway Operation  ............................. 41
   6.1.  Extensions to Binding Update List Entry Data Structure ... 42
   6.2.  Mobile Node's Policy Profile ............................. 43
   6.3.  Supported Access Link Types  ............................. 44
   6.4.  Supported Address Configuration Modes  ................... 44
   6.5.  Access Authentication and Mobile Node Identification ..... 45
   6.6.  Acquiring Mobile Node's Identifier ....................... 45
   6.7.  Home Network Emulation ................................... 46
   6.8.  Link-local and Global Address Uniqueness ................. 46
   6.9.  Signaling Considerations ................................. 48
     6.9.1.  Binding Registrations  ............................... 48
     6.9.2.  Router Solicitation Messages ......................... 56
     6.9.3.  Default-Router ....................................... 57
     6.9.4.  Retransmissions and Rate Limiting  ................... 58
     6.9.5.  Path MTU Discovery ................................... 59
   6.10. Routing Considerations ................................... 60

Gundavelli, et al. Standards Track [Page 2] RFC 5213 Proxy Mobile IPv6 August 2008

     6.10.1. Transport Network  ................................... 60
     6.10.2. Tunneling and Encapsulation Modes  ................... 61
     6.10.3. Local Routing  ....................................... 62
     6.10.4. Tunnel Management  ................................... 62
     6.10.5. Forwarding Rules ..................................... 62
   6.11. Supporting DHCP-Based Address Configuration on the
         Access Link  ............................................. 64
   6.12. Home Network Prefix Renumbering  ......................... 66
   6.13. Mobile Node Detachment Detection and Resource Cleanup  ... 66
   6.14. Allowing Network Access to Other IPv6 Nodes  ............. 67
 7.  Mobile Node Operation  ....................................... 67
   7.1.  Moving into a Proxy Mobile IPv6 Domain ................... 67
   7.2.  Roaming in the Proxy Mobile IPv6 Domain  ................. 69
 8.  Message Formats  ............................................. 69
   8.1.  Proxy Binding Update Message ............................. 69
   8.2.  Proxy Binding Acknowledgement Message  ................... 71
   8.3.  Home Network Prefix Option ............................... 72
   8.4.  Handoff Indicator Option ................................. 73
   8.5.  Access Technology Type Option  ........................... 74
   8.6.  Mobile Node Link-layer Identifier Option ................. 76
   8.7.  Link-local Address Option  ............................... 77
   8.8.  Timestamp Option ......................................... 77
   8.9.  Status Values  ........................................... 78
 9.  Protocol Configuration Variables ............................. 80
   9.1.  Local Mobility Anchor - Configuration Variables  ......... 80
   9.2.  Mobile Access Gateway - Configuration Variables  ......... 81
   9.3.  Proxy Mobile IPv6 Domain - Configuration Variables ....... 82
 10. IANA Considerations  ......................................... 83
 11. Security Considerations  ..................................... 84
 12. Acknowledgements ............................................. 85
 13. References ................................................... 86
   13.1. Normative References ..................................... 86
   13.2. Informative References ................................... 87
 Appendix A.  Proxy Mobile IPv6 Interactions with AAA
              Infrastructure  ..................................... 89
 Appendix B.  Routing State ....................................... 89

Gundavelli, et al. Standards Track [Page 3] RFC 5213 Proxy Mobile IPv6 August 2008

1. Introduction

 IP mobility for IPv6 hosts is specified in Mobile IPv6 [RFC3775].
 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 [RFC3775] 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 [RFC3775] 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 that are designed to support mobility would be
 agnostic to the capability in the IPv6 stack of the nodes that it
 serves.  IP mobility for nodes that have mobile IP client
 functionality in the IPv6 stack as well as those nodes that 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 [RFC4830].  Proxy Mobile
 IPv6 is a solution that addresses these issues and requirements.

Gundavelli, et al. Standards Track [Page 4] RFC 5213 Proxy Mobile IPv6 August 2008

2. Conventions and Terminology

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 [RFC2119].

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
 [RFC3775].
 This document adopts the terms, Local Mobility Anchor (LMA) and
 Mobile Access Gateway (MAG) from the NETLMM Goals document [RFC4831].
 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 set up 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 a
    Proxy Mobile IPv6 domain.  It is the topological anchor point for
    the mobile node's home network prefix(es) 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 [RFC3775] 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 on an access router 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, et al. Standards Track [Page 5] RFC 5213 Proxy Mobile IPv6 August 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 an IPv4-only node, IPv6-only node, or a
    dual-stack node and 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 global 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 which 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 [IPV4-PMIP6].
 Proxy Care-of Address (Proxy-CoA)
    Proxy-CoA is the global address configured on the egress 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 [IPV4-PMIP6].
 Mobile Node's Home Network Prefix (MN-HNP)
    The MN-HNP is a prefix assigned to the link between the mobile
    node and the mobile access gateway.  More than one prefix can be
    assigned to the link between the mobile node and the mobile access
    gateway, in which case, all of the assigned prefixes are managed
    as a set associated with a mobility session.  The mobile node
    configures its interface with one or more addresses from its home
    network prefix(es).  If the mobile node connects to the Proxy
    Mobile IPv6 domain through multiple interfaces, simultaneously,
    each of the attached interfaces will be assigned a unique set of
    home network prefixes, and all the prefixes assigned to a given
    interface of a mobile node will be managed under one mobility
    session.  For example, home network prefixes P1 and P2 assigned to

Gundavelli, et al. Standards Track [Page 6] RFC 5213 Proxy Mobile IPv6 August 2008

    interface I1 will be managed under one mobility session and
    prefixes P3, P4, and P5 assigned to interface I2 of the mobile
    node will be managed under a different mobility session.
    Additionally, in some configurations the assigned prefix can be of
    128-bit prefix length.
 Mobile Node's Home Address (MN-HoA)
    MN-HoA is an address from a mobile node's home network prefix.
    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.  If the mobile node uses more than one address
    from its home network prefix(es), any one of these addresses is
    referred to as mobile node's home address.  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(es) and are not always
    aware of the exact address(es) that the mobile node configured on
    its interface from its home network prefix(es).  However, in some
    configurations and based on the enabled address configuration
    modes on the access link, the mobility entities in the network can
    be certain about the exact address(es) configured by the mobile
    node.
 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 same 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
    for predictably identifying a mobile node.  This is typically an
    identifier such as a Network Access Identifier (NAI) [RFC4282] or
    other identifier such as a Media Access Control (MAC) address.

Gundavelli, et al. Standards Track [Page 7] RFC 5213 Proxy Mobile IPv6 August 2008

 Mobile Node Link-layer Identifier (MN-LL-Identifier)
    An identifier that identifies the attached interface of a mobile
    node.  For those interfaces that have a link-layer identifier,
    this identifier can be based on that.  The link-layer identifier,
    in some cases, is generated by the mobile node and conveyed to the
    mobile access gateway.  This identifier of the attached interface
    must be stable, as seen by any of the mobile access gateways in a
    given Proxy Mobile IPv6 domain.  In some other cases, there might
    not be any link-layer identifier associated with the mobile node's
    interface.  An identifier value of ALL_ZERO is not considered a
    valid identifier and cannot be used as an interface identifier.
 Policy Profile
    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 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 home network prefix(es) assigned to a given
    interface of a mobile node and its current care-of address (Proxy-
    CoA).
 Proxy Binding Acknowledgement (PBA)
    A reply message sent by a local mobility anchor in response to a
    Proxy Binding Update message that it received from a mobile access
    gateway.
 Per-MN-Prefix and Shared-Prefix Models
    The term Per-MN-Prefix model is used to refer to an addressing
    model where there is a unique network prefix or prefixes assigned
    for each node.  The term Shared-Prefix model is used to refer to
    an addressing model where the prefix(es) are shared by more than
    one node.  This specification supports the Per-MN-Prefix model and
    does not support the Shared-Prefix model.

Gundavelli, et al. Standards Track [Page 8] RFC 5213 Proxy Mobile IPv6 August 2008

 Mobility Session
    In the context of Proxy Mobile IPv6 specification, the term
    mobility session refers to the creation or existence of state
    associated with the mobile node's mobility binding on the local
    mobility anchor and on the serving mobile access gateway.
 DHCP
    Throughout this document, the acronym DHCP refers to DHCP for
    IPv6, as defined in [RFC3315].
 ALL_ZERO and NON_ZERO
    Protocol message fields initialized with value 0 in each byte of
    the field.  For example, an 8-byte link-layer identifier field
    with the value set to 0 in each of the 8 bytes, or an IPv6 address
    with the value 0 in all of the 16 bytes.  Conversely, the term
    NON_ZERO is used to refer to any value other than an ALL_ZERO
    value.

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
 [RFC3775].
 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
 set up 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(es).  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.  There can be multiple local mobility anchors in a Proxy
 Mobile IPv6 domain each serving a different group of mobile nodes.
 The architecture of a Proxy Mobile IPv6 domain is shown in Figure 1.

Gundavelli, et al. Standards Track [Page 9] RFC 5213 Proxy Mobile IPv6 August 2008

            +----+                +----+
            |LMA1|                |LMA2|
            +----+                +----+
     LMAA1 -> |                      | <-- LMAA2
              |                      |
              \\                    //\\
               \\                  //  \\
                \\                //    \\
             +---\\------------- //------\\----+
            (     \\  IPv4/IPv6 //        \\    )
            (      \\  Network //          \\   )
             +------\\--------//------------\\-+
                     \\      //              \\
                      \\    //                \\
                       \\  //                  \\
           Proxy-CoA1--> |                      | <-- Proxy-CoA2
                      +----+                 +----+
                      |MAG1|-----{MN2}       |MAG2|
                      +----+    |            +----+
                        |       |               |
           MN-HNP1 -->  |     MN-HNP2           | <-- MN-HNP3, MN-HNP4
                      {MN1}                   {MN3}
                  Figure 1: Proxy Mobile IPv6 Domain
 When 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 mobile node is authorized for
 network-based mobility service, 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(es), the
 default-router address on the link, and other related configuration
 parameters.  From the perspective of each mobile node, the entire
 Proxy Mobile IPv6 domain appears as a single link, the network
 ensures that the mobile node does not detect any change with respect
 to its layer-3 attachment even after changing its point of attachment
 in the network.

Gundavelli, et al. Standards Track [Page 10] RFC 5213 Proxy Mobile IPv6 August 2008

 The mobile node may be an IPv4-only node, IPv6-only node, or a dual-
 stack (IPv4/v6) node.  Based on the policy profile information that
 indicates the type of address or prefixes to be assigned for the
 mobile node in the network, the mobile node will be able to obtain an
 IPv4, IPv6, or dual IPv4/IPv6 address and move anywhere in that Proxy
 Mobile IPv6 domain.  However, this specification only supports IPv6
 address/prefix mobility with the transport network being IPv6.  The
 support for IPv4 addressing or an IPv4 transport network is specified
 in the companion document [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 set of home network prefixes for each of the
 connected interfaces.  The mobile node will be able to configure
 address(es) on those interfaces from the respective home network
 prefix(es).  However, if the mobile node performs a handoff by moving
 its address configuration from one interface to the other, and if the
 local mobility anchor receives a handoff hint from the serving mobile
 access gateway about the same, the local mobility anchor will assign
 the same home network prefix(es) that it previously assigned prior to
 the handoff.  The mobile node will also be able to perform a handoff
 by changing its point of attachment from one mobile access gateway to
 a different mobile access gateway using the same interface and will
 be able to retain the address configuration on the attached
 interface.

Gundavelli, et al. Standards Track [Page 11] RFC 5213 Proxy Mobile IPv6 August 2008

+-----+                +-----+                +-----+
| MN  |                | MAG |                | LMA |
+-----+                +-----+                +-----+
   |                      |                      |

MN Attached | |

   |                      |                      |
   |       MN Attached Event from MN/Network     |
   |        (Acquire MN-Id and Profile)          |
   |                      |                      |
   |--- Rtr Sol --------->|                      |
   |                      |                      |
   |                      |--- PBU ------------->|
   |                      |                      |
   |                      |                  Accept PBU
   |                      | (Allocate MN-HNP(s), Setup BCE and Tunnel)
   |                      |                      |
   |                      |<------------- PBA ---|
   |                      |                      |
   |                 Accept PBA                  |
   |          (Set Up Tunnel and Routing)        |
   |                      |                      |
   |                      |==== Bi-Dir Tunnel ===|
   |                      |                      |
   |<--------- 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.  The Router Solicitation message from
 the mobile node may arrive at any time after the mobile node's
 attachment and has no strict ordering relation with the other
 messages in the call flow.
 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(es).  It also creates the Binding
 Cache entry and sets up its endpoint of the bi-directional tunnel to
 the mobile access gateway.

Gundavelli, et al. Standards Track [Page 12] RFC 5213 Proxy Mobile IPv6 August 2008

 The mobile access gateway on receiving the Proxy Binding
 Acknowledgement message sets up its endpoint of the bi-directional
 tunnel to the local mobility anchor and also sets up the forwarding
 for the mobile node's traffic.  At this point, the mobile access
 gateway has 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(es) as the hosted on-link prefix(es).
 The mobile node, on receiving these Router Advertisement messages on
 the access link, attempts to configure its interface using either
 stateful or stateless address configuration modes, based on the modes
 that are permitted on that access link as indicated in Router
 Advertisement messages.  At the end of a successful address
 configuration procedure, the mobile node has one or more addresses
 from its home network prefix(es).
 After address configuration, the mobile node has one or more valid
 addresses from its home network prefix(es) 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 any one or more of the addresses
 from its home network prefix(es).
 The local mobility anchor, being the topological anchor point for the
 mobile node's home network prefix(es), receives any packets that are
 sent to the mobile node by any node in or outside the Proxy Mobile
 IPv6 domain.  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.  However, in some
 cases, the traffic sent from a correspondent node that is locally
 connected to the mobile access gateway may not be received by the
 local mobility anchor and may be routed locally by the mobile access
 gateway (refer to Section 6.10.3).
 The mobile access gateway acts as the default router on the point-to-
 point link shared with the mobile node.  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.  However, in some
 cases, the traffic sent to a correspondent node that is locally
 connected to the mobile access gateway may be locally routed by the
 mobile access gateway (refer to Section 6.10.3).

Gundavelli, et al. Standards Track [Page 13] RFC 5213 Proxy Mobile IPv6 August 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 received
     |                |                |     from MN or from network
     |                |                |   (Acquire MN-Id and Profile)
     |                |                |                |
     |--- Rtr Sol ------------------------------------->|
                             ....
                                  Registration steps as in Fig. 2.
                             ....
     |                |                |==Bi-Dir Tunnel=|
     |                |                |                |
     |<------------------------------------ Rtr Adv ----|
     |                |                |                |
 MN retains HoA/HNP(s)
     |                |                |                |
          Figure 3: Mobile Node Handoff - Signaling Call Flow
 Figure 3 shows the signaling call flow for the mobile node's handoff
 from the previously attached mobile access gateway (p-MAG) to the
 newly attached mobile access gateway (n-MAG).  This call flow only
 reflects 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.  It will signal the local mobility
 anchor and will remove the binding and routing state for that mobile
 node.  The local mobility anchor, upon receiving this request, will
 identify the corresponding mobility session for which the request was

Gundavelli, et al. Standards Track [Page 14] RFC 5213 Proxy Mobile IPv6 August 2008

 received, and accepts the request after which it waits for a certain
 amount of time to allow the mobile access gateway on the new link to
 update the binding.  However, if it does not receive any Proxy
 Binding Update message within the given amount of time, it will
 delete the binding cache entry.
 The mobile access gateway on the new access link, upon detecting the
 mobile node on its access link, will signal the local mobility anchor
 to update the binding state.  After completion of the signaling, the
 serving mobile access gateway will send the Router Advertisements
 containing the mobile node's home network prefix(es), and this will
 ensure the mobile node will not detect any change with respect to the
 layer-3 attachment of its interface.

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 [RFC4301].  IPsec is a mandatory-to-implement security
 mechanism.  However, additional documents may specify alternative
 mechanisms and the mobility entities can enable a specific mechanism
 for securing Proxy Mobile IPv6 signaling messages, based on either a
 static configuration or after a dynamic negotiation using any
 standard security negotiation protocols.  As in Mobile IPv6
 [RFC3775], the use of IPsec for protecting a mobile node's data
 traffic is optional.
 IPsec Encapsulating Security Payload (ESP) [RFC4303] in transport
 mode with mandatory integrity protection SHOULD be used for
 protecting the signaling messages.  Confidentiality protection of
 these messages is not required.
 IPsec ESP [RFC4303] in tunnel mode MAY be used to protect the mobile
 node's tunneled data traffic, if protection of data traffic is
 required.
 Internet Key Exchange Protocol version 2 (IKEv2) [RFC4306] SHOULD be
 used to set up 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 [RFC4306], for mutual
 authentication.

Gundavelli, et al. Standards Track [Page 15] RFC 5213 Proxy Mobile IPv6 August 2008

 The Mobile IPv6 specification [RFC3775] 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 Authentication, Authorization, and Accounting (AAA) may be
 employed, but these are outside the scope of this specification.
 Unlike in Mobile IPv6 [RFC3775], these signaling messages do not
 carry either the Home Address destination option or the Type 2
 Routing header, and hence the policy entries and security association
 selectors stay the same and require no special IPsec related
 considerations.

4.1. Peer Authorization Database (PAD) Example Entries

 This section describes PAD entries [RFC4301] 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.
 In the example shown below, the identity of the local mobility anchor
 is assumed to be lma_identity_1 and the identity of the mobile access
 gateway is assumed to be mag_identity_1.
     mobile access gateway PAD:
       - IF remote_identity = lma_identity_1
            Then authenticate (shared secret/certificate/EAP)
            and authorize CHILD_SAs for remote address lma_address_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

Gundavelli, et al. Standards Track [Page 16] RFC 5213 Proxy Mobile IPv6 August 2008

 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 (SPD) Example Entries

 This section describes the security policy entries [RFC4301] 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 example shown below, the identity of the mobile access gateway
 is assumed to be mag_identity_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.  The acronym MH
 represents the protocol number for the Mobility Header [RFC3775],
 while the terms local_mh_type and remote_mh_type stand for local
 mobility header type and remote mobility header type, respectively.
    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_identity_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 [RFC3775] and the extensions defined in this
 specification.  A home agent with these modifications and enhanced
 capabilities for supporting the Proxy Mobile IPv6 protocol is
 referred to as a local mobility anchor.
 This section describes the operational details of the local mobility
 anchor.

Gundavelli, et al. Standards Track [Page 17] RFC 5213 Proxy Mobile IPv6 August 2008

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.  A Binding Cache entry is a
 conceptual data structure, described in Section 9.1 of [RFC3775].
 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 set to value 1
    for Binding Cache entries that are proxy registrations and is set
    to value 0 for all other entries.
 o  The identifier of the registered mobile node, MN-Identifier.  This
    identifier is obtained from the Mobile Node Identifier Option
    [RFC4283] present in the received Proxy Binding Update message.
 o  The link-layer identifier of the mobile node's connected interface
    on the access link.  This identifier can be acquired from the
    Mobile Node Link-layer Identifier option, present in the received
    Proxy Binding Update message.  If the option was not present in
    the request, this variable length field MUST be set to two
    (octets) and MUST be initialized to a value of ALL_ZERO.
 o  The link-local address of the mobile access gateway on the point-
    to-point link shared with the mobile node.  This is generated by
    the local mobility anchor after accepting the initial Proxy
    Binding Update message.
 o  A list of IPv6 home network prefixes assigned to the mobile node's
    connected interface.  The home network prefix(es) may have been
    statically configured in the mobile node's policy profile, or,
    they may have been dynamically allocated by the local mobility
    anchor.  Each one of these prefix entries will also include the
    corresponding prefix length.
 o  The tunnel interface identifier (tunnel-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, by which the mobile node is currently
    attached.  This is obtained from the Access Technology Type
    option, present in the Proxy Binding Update message.

Gundavelli, et al. Standards Track [Page 18] RFC 5213 Proxy Mobile IPv6 August 2008

 o  The 64-bit timestamp value of the most recently accepted Proxy
    Binding Update message 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 message (i.e., when the sequence-number-based
    scheme is in use), the value MUST be set to ALL_ZERO.
 Typically, any one of the mobile node's home network prefixes from
 its mobility session may be used as a key for locating its Binding
 Cache entry in all cases except when there has been a 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(es) assigned to
 that mobility session.  In such handoff cases, the Binding Cache
 entry can be located under the considerations specified in Section
 5.4.1.

5.2. Supported Home Network Prefix Models

 This specification supports the Per-MN-Prefix model and does not
 support the Shared-Prefix model.  According to the Per-MN-Prefix
 model, home network prefix(es) assigned to a mobile node are for that
 mobile node's exclusive use and no other node shares an address from
 that prefix (other than the Subnet-Router anycast address [RFC4291]
 that is used by the mobile access gateway hosting that prefix on that
 link).
 There may be more than one prefix assigned to a given interface of
 the mobile node; all of those assigned prefixes MUST be unique to
 that mobile node, and all are part of exactly one mobility session.
 If the mobile node simultaneously attaches to the Proxy Mobile IPv6
 domain through multiple interfaces, each of the attached interfaces
 MUST be assigned one or more unique prefixes.  Prefixes that are not
 assigned to the same interface MUST NOT be managed under the same
 mobility session.
 The mobile node's home network prefix(es) assigned to a given
 interface of a mobile node (part of a mobility session) will be
 hosted on the access link where the mobile node is attached (using
 that interface).  The local mobility anchor is not required to
 perform any proxy Neighbor Discovery (ND) operations [RFC4861] for
 defending the mobile node's home address(es), as the prefixes are not
 locally hosted on the local mobility anchor.  However, from the
 routing perspective, the home network prefix(es) is topologically
 anchored on the local mobility anchor.

Gundavelli, et al. Standards Track [Page 19] RFC 5213 Proxy Mobile IPv6 August 2008

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 Proxy Binding Updates

 1.   The received Proxy Binding Update message (a Binding Update
      message with the (P) flag set to value of 1, format specified in
      Section 8.1) MUST be authenticated as described in Section 4.
      When IPsec is used for message authentication, the Security
      Parameter Index (SPI) in the IPsec header [RFC4306] 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 of [RFC3775] when processing the Mobility Header in
      the received Proxy Binding Update message.
 3.   The local mobility anchor MUST ignore the check, specified in
      Section 10.3.1 of [RFC3775], related to the presence of the Home
      Address destination option in the Proxy Binding Update message.
 4.   The local mobility anchor MUST identify the mobile node from the
      identifier present in the Mobile Node Identifier option
      [RFC4283] of the Proxy Binding Update message.  If the Mobile
      Node Identifier option is not present in the Proxy Binding
      Update message, 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 that the sender is a
      trusted mobile access gateway authorized to send Proxy Binding
      Update messages 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 messages for the
      identified mobile node, it MUST reject the request and send a
      Proxy Binding Acknowledgement message with the Status field set
      to MAG_NOT_AUTHORIZED_FOR_PROXY_REG (not authorized to send
      proxy binding updates).

Gundavelli, et al. Standards Track [Page 20] RFC 5213 Proxy Mobile IPv6 August 2008

 7.   If the local mobility anchor cannot identify the mobile node
      based on the identifier present in the Mobile Node Identifier
      option [RFC4283] of the Proxy Binding Update message, it MUST
      reject the request and send a Proxy Binding Acknowledgement
      message with the Status field set to
      NOT_LMA_FOR_THIS_MOBILE_NODE (Not a 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 the 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 message.
 10.  If there is no Home Network Prefix option(s) (with any value)
      present in the Proxy Binding Update message, the local mobility
      anchor MUST reject the request and send a Proxy Binding
      Acknowledgement message with the Status field set to
      MISSING_HOME_NETWORK_PREFIX_OPTION (Missing Home Network Prefix
      option).
 11.  If the Handoff Indicator option is not present in the Proxy
      Binding Update message, the local mobility anchor MUST reject
      the request and send a Proxy Binding Acknowledgement message
      with the 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 message, the local mobility anchor MUST reject
      the request and send a Proxy Binding Acknowledgement message
      with the 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 message 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 need to be applied.

Gundavelli, et al. Standards Track [Page 21] RFC 5213 Proxy Mobile IPv6 August 2008

  • If the received Proxy Binding Update message has the lifetime

value of zero, considerations from Section 5.3.5 (Binding De-

         Registration) MUST be applied.
  • If the Proxy-CoA 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),
         considerations from Section 5.3.3 (Binding LIfetime Extension
         - No handoff) 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 there is at least one instance of the Home Network Prefix
     option present in the Proxy Binding Update message with the
     prefix value set to ALL_ZERO, the local mobility anchor MUST
     allocate one or more home network prefixes to the mobile node and
     assign it to the new mobility session created for the mobile
     node.  The local mobility anchor MUST ensure the allocated
     prefix(es) is not in use by any other node or mobility session.
     The decision on how many prefixes to be allocated for the
     attached interface can be based on a global policy or a policy
     specific to that mobile node.  However, when stateful address
     autoconfiguration using DHCP is supported on the link,
     considerations from Section 6.11 MUST be applied for the prefix
     assignment.
 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 the Status
     field set to 130 (Insufficient resources).
 3.  If there are one or more Home Network Prefix options present in
     the Proxy Binding Update message (with each of the prefixes set
     to a NON_ZERO value), the local mobility anchor, before accepting
     that request, MUST ensure each one of those prefixes is owned by
     the local mobility anchor, and further that the mobile node is
     authorized to use these prefixes.  If the mobile node is not
     authorized to use any one or more of those prefixes, the local
     mobility anchor MUST reject the request and send a Proxy Binding

Gundavelli, et al. Standards Track [Page 22] RFC 5213 Proxy Mobile IPv6 August 2008

     Acknowledgement message with the Status field set to
     NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX (mobile node not
     authorized for one or more of the requesting home network
     prefixes).
 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.  If there is no existing bi-directional tunnel to the mobile
     access gateway that sent the request, the local mobility anchor
     MUST establish a bi-directional tunnel to that mobile access
     gateway.  Considerations from Section 5.6.1 MUST be applied for
     managing the dynamically created bi-directional tunnel.
 6.  The local mobility anchor MUST create a prefix route(s) over the
     tunnel to the mobile access gateway for forwarding any traffic
     received for the mobile node's home network prefix(es) associated
     with this mobility session.  The created tunnel and the routing
     state MUST result in the forwarding behavior on the local
     mobility anchor as specified in Section 5.6.2.
 7.  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 message for extending the
     binding lifetime, received from the same mobile access gateway
     (if the Proxy-CoA in the Binding Cache entry is the same as the
     Proxy-CoA in the request) that last updated the binding, the
     local mobility anchor MUST update the Binding Cache entry with
     the accepted registration values.
 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, et al. Standards Track [Page 23] RFC 5213 Proxy Mobile IPv6 August 2008

5.3.4. Binding Lifetime Extension (After Handoff)

 1.  Upon accepting the Proxy Binding Update message for extending the
     binding lifetime, received from a new mobile access gateway (if
     the Proxy-CoA in the Binding Cache entry does not match the
     Proxy-CoA in the request) where the mobile node's mobility
     session is handed off, the local mobility anchor MUST update the
     Binding Cache entry with the accepted registration values.
 2.  The local mobility anchor MUST remove the previously created
     route(s) for the mobile node's home network prefix(es) associated
     with this mobility session.  Additionally, if there are no other
     mobile nodes sharing the dynamically created bi-directional
     tunnel to the previous mobile access gateway, the tunnel SHOULD
     be deleted, applying considerations from section 5.6.1 (if the
     tunnel is a dynamically created tunnel and not a fixed pre-
     established tunnel).
 3.  If there is no existing bi-directional tunnel to the mobile
     access gateway that sent the request, the local mobility anchor
     MUST establish a bi-directional tunnel to that mobile access
     gateway.  Considerations from Section 5.6.1 MUST be applied for
     managing the dynamically created bi-directional tunnel.
 4.  The local mobility anchor MUST create prefix route(s) over the
     tunnel to the mobile access gateway for forwarding any traffic
     received for the mobile node's home network prefix(es) associated
     with that mobility session.  The created tunnel and routing state
     MUST result in the forwarding behavior on the local mobility
     anchor as specified in Section 5.6.2.
 5.  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 message 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 field in
     the Binding Cache entry, the local mobility anchor MUST ignore
     the request.
 2.  Upon accepting the Proxy Binding Update message, with the
     lifetime value of zero, the local mobility anchor MUST wait for
     MinDelayBeforeBCEDelete amount of time, before it deletes the

Gundavelli, et al. Standards Track [Page 24] RFC 5213 Proxy Mobile IPv6 August 2008

     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.

  • During this wait period, if the local mobility anchor receives

a valid Proxy Binding Update message 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 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 messages for

        this mobility session, then it MUST delete the Binding Cache
        entry and remove the routing state created for that mobility
        session.  The local mobility anchor can potentially reassign
        the prefix(es) associated with this mobility session to other
        mobile nodes.

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 to value of 1 */
            Mobility Options
             - Mobile Node Identifier option            (mandatory)
             - Home Network Prefix option(s)            (mandatory)
             - Handoff Indicator option                 (mandatory)
             - Access Technology Type option            (mandatory)
             - Timestamp option                         (optional)
             - Mobile Node Link-layer 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 message.

Gundavelli, et al. Standards Track [Page 25] RFC 5213 Proxy Mobile IPv6 August 2008

 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 message.  When there is no Alternate Care-of Address option
    present in the request, the destination address is the same as the
    Proxy-CoA; otherwise, the address may not be the same as the
    Proxy-CoA.
 o  The Mobile Node Identifier option [RFC4283] MUST be present.  The
    identifier field in the option MUST be copied from the Mobile Node
    Identifier option in the received Proxy Binding Update message.
    If the option was not present in the request, the identifier in
    the option MUST be set to a zero length identifier.
 o  At least one 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 Proxy Binding Update is rejected, all the

       Home Network Prefix options that were present in the request
       (along with their prefix values) MUST be present in the reply.
       But, if there was no Home Network Prefix option present in the
       request, then there MUST be only one Home Network Prefix option
       with the value in the option set to ALL_ZERO.
  • For all other cases, there MUST be a Home Network Prefix option

for each of the assigned home network prefixes (for that

       mobility session), and with the prefix value in the option set
       to the allocated prefix value.
 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 message.  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
    message.  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 only if the same option was
    present in the received Proxy Binding Update message and MUST NOT
    be present otherwise.  Considerations from Section 5.5 must be
    applied for constructing the Timestamp option.
 o  The Mobile Node Link-layer Identifier option MUST be present only
    if the same option was present in the received Proxy Binding
    Update message and MUST NOT be present otherwise.  The link-layer

Gundavelli, et al. Standards Track [Page 26] RFC 5213 Proxy Mobile IPv6 August 2008

    identifier value MUST be copied from the Mobile Node Link-layer
    Identifier option present in the received Proxy Binding Update
    message.
 o  The Link-local Address option MUST be present only if the same
    option was present in the received Proxy Binding Update message
    and MUST NOT be present otherwise.  If the Status field in the
    reply is set to a value greater than or equal to 128, i.e., if the
    Proxy Binding Update is rejected, then the link-local address from
    the request MUST be copied to the Link-local Address option in the
    reply, otherwise the following considerations apply.
  • If the received Proxy Binding Update message has the Link-local

Address option with ALL_ZERO value and if there is an existing

       Binding Cache entry associated with this request, then the
       link-local address from the Binding Cache entry MUST be copied
       to the Link-local Address option in the reply.
  • If the received Proxy Binding Update message has the Link-local

Address option with ALL_ZERO value and if there is no existing

       Binding Cache entry associated with this request, then the
       local mobility anchor MUST generate the link-local address that
       the mobile access gateway can use on the point-to-point link
       shared with the mobile node.  This generated address MUST be
       copied to the Link-local Address option in the reply.  The same
       address MUST also be copied to the link-local address field of
       Binding Cache entry created for this mobility session.
  • If the received Proxy Binding Update message has the Link-local

Address option with NON_ZERO value, then the link-local address

       from the request MUST be copied to the Link-local Address
       option in the reply.  The same address MUST also be copied to
       the link-local address field of the Binding Cache entry
       associated with this request (after creating the Binding Cache
       entry, if one does not exist).
 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 [RFC3775], 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 for simultaneous access.  The
 following are the key aspects of this multihoming support.

Gundavelli, et al. Standards Track [Page 27] RFC 5213 Proxy Mobile IPv6 August 2008

 o  When a mobile node connects to a Proxy Mobile IPv6 domain through
    multiple interfaces for simultaneous access, the local mobility
    anchor MUST allocate a mobility session for each of the attached
    interfaces.  Each mobility session should be managed under a
    separate Binding Cache entry and with its own lifetime.
 o  The local mobility anchor MAY allocate more than one home network
    prefix for a given interface of the mobile node.  However, all the
    prefixes associated with a given interface MUST be managed as part
    of one mobility session, associated with that interface.
 o  The local mobility anchor MUST allow for a handoff between two
    different interfaces of a mobile node.  In such a scenario, all
    the home network prefixes associated with one interface (part of
    one mobility session) will be associated with a different
    interface of the mobile node.  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.

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 message, the local
 mobility anchor MUST apply the following multihoming considerations
 (in the below specified order, starting with Section 5.4.1.1).  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 | +=====================================================================+ | At least one HNP Option with NON_ZERO Value | +=====================================================================+ | ATT | +=====================================================================+ | MN-LL-Identifier Opt Present | MN-LL-Identifier Opt Not Present | +=====================================================================+ | HI | +==================================+==================================+ | BCE Lookup Key: Any of the Home Network Prefixes from the request | +=====================================================================+

 Figure 7: Binding Cache Entry (BCE) Lookup Using Home Network Prefix

Gundavelli, et al. Standards Track [Page 28] RFC 5213 Proxy Mobile IPv6 August 2008

 If there is at least one Home Network Prefix option present in the
 request with a NON_ZERO prefix value and irrespective of the presence
 of the Mobile Node Link-layer Identifier option in the request, the
 following considerations MUST be applied.  If there is more than one
 instance of the Home Network Prefix option, any one of the Home
 Network Prefix options present in the request (with NON_ZERO prefix
 value) can be used for locating the Binding Cache entry.
 1.  The local mobility anchor MUST verify if there is an existing
     Binding Cache entry with one of its home network prefixes
     matching the prefix value in one of the Home Network Prefix
     options of the received Proxy Binding Update message.
 2.  If a Binding Cache entry does not exist (with one of its home
     network prefixes in the Binding Cache entry matching the prefix
     value in one of the Home Network Prefix options of the received
     Proxy Binding Update message), the request MUST be considered as
     a request for creating a new mobility session.
 3.  If there exists a Binding Cache entry (with one of its home
     network prefixes in the Binding Cache entry matching the prefix
     value in one of the Home Network Prefix options of the received
     Proxy Binding Update message), but 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 message, 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 one or more of the requesting home network
     prefixes).
 4.  If there exists a Binding Cache entry (matching MN-Identifier and
     one of its home network prefixes in the Binding Cache entry
     matching the prefix value in one of the Home Network Prefix
     options of the received Proxy Binding Update message), but if all
     the prefixes in the request do not match all the prefixes in the
     Binding Cache entry, or if they do not match in count, then the
     local mobility anchor MUST reject the request with the Status
     field value set to BCE_PBU_PREFIX_SET_DO_NOT_MATCH (all the home
     network prefixes listed in the BCE do not match all the prefixes
     in the received PBU).
 5.  If there exists a Binding Cache entry (matching MN-Identifier and
     all the home network prefixes in the Binding Cache entry matching
     all the home network prefixes in the received Proxy Binding
     Update message) and if any one or more of these below stated
     conditions are true, the request MUST be considered as a request
     for updating that Binding Cache entry.

Gundavelli, et al. Standards Track [Page 29] RFC 5213 Proxy Mobile IPv6 August 2008

  • If there is a Mobile Node Link-layer Identifier option present

in the request and if the link-layer identifier in the option

        matches the link-layer identifier of the Binding Cache entry
        and the access technology type in the Access Technology Type
        option present in the request matches the access technology
        type in the Binding Cache entry.
  • 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 Link-layer Identifier option

present in the request, the link-layer 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 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.
 6.  For all other cases, the message MUST be considered as a request
     for creating a new mobility session.  However, if the received
     Proxy Binding Update message has the lifetime value of zero and
     if the request cannot be associated with any existing mobility
     session, the message MUST be silently ignored.

Gundavelli, et al. Standards Track [Page 30] RFC 5213 Proxy Mobile IPv6 August 2008

5.4.1.2. Mobile Node Link-layer Identifier Option Present in the

        Request

+=====================================================================+ | Registration/De-Registration Message | +=====================================================================+ | No HNP option with a NON_ZERO Value | +=====================================================================+ | ATT | +=====================================================================+ | MN-LL-Identifier Option Present (NON_ZERO Value) | +=====================================================================+ | HI | +==================================+==================================+ | BCE Lookup Keys: (MN-Identifier + ATT + MN-LL-Identifier) | +=====================================================================+

           Figure 8: BCE Lookup Using Link-layer Identifier
 If there is no Home Network Prefix option present in the request with
 a NON_ZERO prefix value, but if there is a Mobile Node Link-layer
 Identifier option present in the request, then the following
 considerations MUST be applied for locating the Binding Cache entry.
 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 link-layer identifier value
     matching the identifier in the received Mobile Node Link-layer
     Identifier option.
 2.  If there exists a Binding Cache entry (matching MN-Identifier,
     Access Technology Type (ATT), and MN-LL-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-LL-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.
  • 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 link-layer identifier

Gundavelli, et al. Standards Track [Page 31] RFC 5213 Proxy Mobile IPv6 August 2008

        value.  If there exists only one such entry (matching the MN-
        Identifier), the request MUST be considered as a request for
        updating that Binding Cache entry.
 4.  If there does not exist a Binding Cache entry (matching MN-
     Identifier, ATT, and MN-LL-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 link-layer identifier
        value.  If there exists only one such entry (matching the MN-
        Identifier), the local mobility anchor SHOULD wait until 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 creating a new mobility
        session.  The local mobility anchor MAY also choose to create
        a new mobility session 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.  However, if the received
     Proxy Binding Update message has the lifetime value of zero and
     if the request cannot be associated with any existing mobility
     session, the message MUST be silently ignored.

Gundavelli, et al. Standards Track [Page 32] RFC 5213 Proxy Mobile IPv6 August 2008

5.4.1.3. Mobile Node Link-layer Identifier Option Not Present in the

        Request

+=====================================================================+ | Registration/De-Registration Message | +=====================================================================+ | No HNP option with a NON_ZERO Value | +=====================================================================+ | ATT | +=====================================================================+ | MN-LL-Identifier Option Not Present | +=====================================================================+ | HI | +==================================+==================================+ | BCE Lookup Key: (MN-Identifier) | +=====================================================================+

           Figure 9: BCE Lookup Using Mobile Node Identifier
 If there is no Home Network Prefix option present in the request with
 a NON_ZERO prefix value and if there is also no Mobile Node Link-
 layer Identifier option present in the request, then the following
 considerations MUST be applied for locating the Binding Cache entry.
 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) or set to a value of
     3 (Handoff between mobile access gateways for the same
     interface), then the request MUST be considered as a request for
     updating that Binding Cache entry.
 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 until 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 creating a new mobility session.  The

Gundavelli, et al. Standards Track [Page 33] RFC 5213 Proxy Mobile IPv6 August 2008

     local mobility anchor MAY also choose to create a new mobility
     session without waiting for a de-registration message, and this
     should 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.  However, if the received
     Proxy Binding Update message has the lifetime value of zero and
     if the request cannot be associated with any existing mobility
     session, the message MUST be silently ignored.

5.5. Timestamp Option for Message Ordering

 Mobile IPv6 [RFC3775] 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 [RFC3775], will be insufficient for Proxy Mobile IPv6.
 If the local mobility anchor cannot determine the sending order of
 the received Proxy Binding Update messages, it may potentially
 process an older message sent by a mobile access gateway where the
 mobile node was previously anchored, but delivered out of order,
 resulting in incorrectly updating the mobile node's Binding Cache
 entry and creating a routing state for tunneling the mobile node's
 traffic to the previous mobile access gateway.
 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 [RFC3775].
 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 Proxy Binding Update message for updating a given mobile node's
 binding.

Gundavelli, et al. Standards Track [Page 34] RFC 5213 Proxy Mobile IPv6 August 2008

 Clock drift reduces the effectiveness of the timestamp mechanism.
 The time required for reconnection is the total of the time required
 for the mobile node to roam between two mobile access gateways and
 the time required for the serving mobile access gateway to detect the
 mobile node on its access link and construct the Proxy Binding Update
 message.  If the clock skew on any one of these two neighboring
 mobile access gateways (relative to the common time source used for
 clock synchronization) is more than half this reconnection time, the
 timestamp solution will not predictably work in all cases and hence
 SHOULD NOT be used.
 As an alternative to the Timestamp-based approach, the specification
 also allows the use of Sequence-Number-based scheme, as specified in
 [RFC3775].  However, for this scheme to work, the serving mobile
 access gateway 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 that mobility session.  The sequence number
 MUST be maintained on a mobile node's per mobility session basis and
 MUST be available to the serving mobile access gateway.  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 made available to the
 serving mobile access gateway prior to sending the Proxy Binding
 Update message is outside the scope of this document.
 Using the Timestamp-Based Approach:
 1.  A local mobility anchor implementation MUST support the Timestamp
     option.  If the Timestamp option is present in the received Proxy
     Binding Update 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 the Network Time
     Protocol [RFC4330].  Deployments MAY also adopt other approaches
     suitable for that specific deployment.  Alternatively, if there
     is a mobile node generated timestamp that is increasing at every
     attachment to the access link and if that timestamp is available

Gundavelli, et al. Standards Track [Page 35] RFC 5213 Proxy Mobile IPv6 August 2008

     to the mobile access gateway (e.g., the Timestamp option in the
     SEND [RFC3971] 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 are 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.
 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
     following MUST be true.
  • 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.
        However, if the flag MobileNodeGeneratedTimestampInUse is set
        to a value of 1, the local mobility anchor MUST ignore this
        check and perform only the following check.
  • 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) or if
     the flag MobileNodeGeneratedTimestampInUse is set to value of 1,
     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 message and
     send a Proxy Binding Acknowledgement message with the Status
     field set to TIMESTAMP_LOWER_THAN_PREV_ACCEPTED (Timestamp lower

Gundavelli, et al. Standards Track [Page 36] RFC 5213 Proxy Mobile IPv6 August 2008

     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 the 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 the Sequence-Number-Based Approach:
 1.  If the Timestamp option is not present in the received Proxy
     Binding Update message, the local mobility anchor MUST fall back
     to the Sequence-Number-based scheme.  It MUST process the
     sequence number field as specified in [RFC3775].  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 the Sequence-Number-based scheme,
     as specified in [RFC3775].
 3.  The Sequence-Number-based approach can be used only when there is
     some mechanism (such as context transfer procedure between mobile
     access gateways) that allows the serving mobile access gateway to
     obtain the last sequence number that was sent in a Proxy Binding
     Update message for updating a given mobile node's binding.

5.6. Routing Considerations

5.6.1. Bi-Directional Tunnel Management

 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.  A tunnel hides the topology and enables a mobile node to use
 address(es) from its home network prefix(es) from any access link in
 that Proxy Mobile IPv6 domain.  A tunnel may be created dynamically
 when needed and removed when not needed.  However, implementations
 MAY choose to use static pre-established tunnels instead of
 dynamically creating and tearing them down on a need basis.  The
 following considerations MUST be applied when using dynamically
 created tunnels.

Gundavelli, et al. Standards Track [Page 37] RFC 5213 Proxy Mobile IPv6 August 2008

 o  A bi-directional tunnel MUST be established between the local
    mobility anchor and the mobile access gateway and the local
    mobility anchor with IPv6-in-IPv6 encapsulation, as described in
    [RFC2473].  The tunnel endpoints are the Proxy-CoA and LMAA.
    However, when using IPv4 transport, the endpoints of the tunnel
    are IPv4-LMAA and IPv4-Proxy-CoA with the encapsulation mode as
    specified in [IPV4-PMIP6].
 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 can be set to the
    accepted binding lifetime and can 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.
 o  The tunnel SHOULD be deleted when either the tunnel lifetime
    expires or when there are no mobile nodes sharing the 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(es) 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 the mobile node's home network prefix(es).
 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(es), the local mobility anchor MUST forward the packet
    through the bi-directional tunnel set up for that mobile node.
 o  The format of the tunneled packet is shown below.  Considerations
    from [RFC2473] MUST be applied for IPv6 encapsulation.  However,
    when using IPv4 transport, the format of the packet is as
    described in [IPV4-PMIP6].

Gundavelli, et al. Standards Track [Page 38] RFC 5213 Proxy Mobile IPv6 August 2008

      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 Packet from LMA to MAG
 o  The format of the tunneled packet is shown below, when payload
    protection using IPsec is enabled for the mobile node's data
    traffic.  However, when using IPv4 transport, the format of the
    packet is as described in [IPV4-PMIP6].
      IPv6 header (src= LMAA, dst= Proxy-CoA     /* Tunnel Header */
         ESP Header in tunnel mode               /* ESP Header */
            IPv6 header (src= CN, dst= MN-HoA )  /* Packet Header */
               Upper layer protocols             /* Packet Content*/
    Figure 11: Tunneled Packet from LMA to MAG with Payload Protection
 Forwarding Packets Sent by the Mobile Node:
 o  All the reverse tunneled packets that the local mobility anchor
    received 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.  Considerations from
    [RFC2473] MUST be applied for IPv6 decapsulation.

5.6.3. Explicit Congestion Notification (ECN) Considerations for Proxy

      Mobile IPv6 Tunnels
 This section describes how the ECN information needs to be handled by
 the mobility agents at the tunnel entry and exit points.  The ECN
 considerations for IP tunnels are specified in [RFC3168], and the
 same considerations apply to Proxy Mobile IPv6 tunnels (using IPv6-
 in-IPv6 encapsulation mode).  Specifically, the full-functionality
 option MUST be supported.  The relevant ECN considerations from
 [RFC3168] are summarized here for convenience.
 Encapsulation Considerations:
 o  If the Explicit Congestion Notification (ECN) field in the inner
    header is set to ECT(0) or ECT(1), where ECT stands for ECN-
    Capable Transport (ECT), the ECN field from the inner header MUST
    be copied to the outer header.  Additionally, when payload
    protection using IPsec is enabled for the mobile node's data
    traffic, the ECN considerations from [RFC4301] MUST be applied.

Gundavelli, et al. Standards Track [Page 39] RFC 5213 Proxy Mobile IPv6 August 2008

 Decapsulation Considerations:
 o  If the Explicit Congestion Notification (ECN) field in the inner
    header is set to ECT(0) or ECT(1), and if the ECN field in the
    outer header is set to Congestion Experienced (CE), then the ECN
    field in the inner header MUST be set to CE.  Otherwise, the ECN
    field in the inner header MUST NOT be modified.  Additionally,
    when payload protection using IPsec is enabled for the mobile
    node's data traffic, the ECN considerations from [RFC4301] MUST be
    applied.

5.7. Local Mobility Anchor Address Discovery

 Dynamic Home Agent Address Discovery (DHAAD), as explained in Section
 10.5 of [RFC3775], 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 Agent's 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 Agent's
 anycast address corresponding to the mobile node's home network
 prefix(es), as the prefix(es) 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
 configured to serve a mobile node can be discovered by the mobility
 access gateway entity via other means.  The LMA to be assigned to a
 mobile node 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 [RFC3775] is not
 applicable to Proxy Mobile IPv6.

Gundavelli, et al. Standards Track [Page 40] RFC 5213 Proxy Mobile IPv6 August 2008

5.9. Route Optimization Considerations

 The Route Optimization in Mobile IPv6, as defined in [RFC3775],
 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.
 This specification does not support the Route Optimization specified
 in Mobile IPv6 [RFC3775].  However, this specification does support
 another form of route optimization, as specified in Section 6.10.3.

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
 Proxy Binding Update messages 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
    mobile node's local mobility anchor.
 o  Emulation of the mobile node's home link on the access link by
    sending Router Advertisement messages containing the mobile node's
    home network prefix(es), each prefix carried using the Prefix
    Information option [RFC4861].
 o  Responsible for setting up the forwarding for enabling the mobile
    node to configure one or more addresses from its home network
    prefix(es) and use it from the attached access link.

Gundavelli, et al. Standards Track [Page 41] RFC 5213 Proxy Mobile IPv6 August 2008

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 of
 [RFC3775].
 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 link-layer identifier of the mobile node's connected
    interface.  This 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
    link-layer 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, this variable
    length field MUST be set to two (octets) and MUST be initialized
    to a value of ALL_ZERO.
 o  A list of IPv6 home network prefixes assigned to the mobile node's
    connected interface.  The home network prefix(es) may have been
    statically configured in the mobile node's policy profile, or, may
    have been dynamically allocated by the local mobility anchor.
    Each of these prefix entries will also include the corresponding
    prefix length.
 o  The Link-local address of the mobile access gateway on the access
    link shared with the mobile node.
 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.
 o  The interface identifier (if-id) of the point-to-point link
    between the mobile node and the mobile access gateway.  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.

Gundavelli, et al. Standards Track [Page 42] RFC 5213 Proxy Mobile IPv6 August 2008

 o  The tunnel interface identifier (tunnel-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(es) assigned to the
    mobile node's connected interface.  These prefixes have to be
    maintained on a per-interface basis.  There can be multiple unique
    entries for each interface of the mobile node.  The specific
    details on how the network maintains this association between the
    prefix set and the interfaces, specially during the mobility
    session handoff between interfaces, is outside the scope of this
    document.
 o  The mobile node's IPv6 home network Prefix lifetime.  This
    lifetime will be the same for all the hosted prefixes on the link,
    as they all are part of one mobility session.  This value can also
    be the same for all the mobile node's mobility sessions.
 o  Supported address configuration procedures (Stateful, Stateless,
    or both) for the mobile node in the Proxy Mobile IPv6 domain

Gundavelli, et al. Standards Track [Page 43] RFC 5213 Proxy Mobile IPv6 August 2008

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 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 emulates point-to-point
 delivery between the mobile node and the mobile access gateway for
 all the protocol traffic.
 It is also necessary to be able to identify mobile nodes attaching to
 the link.  Requirements relating to this are covered in Section 6.6.
 Finally, while this specification can operate without link-layer
 indications of node attachment and detachment to the link, the
 existence of such indications either on the network or mobile node
 side improves the resulting performance.

6.4. Supported Address Configuration Modes

 A mobile node in the Proxy Mobile IPv6 domain can configure one or
 more global IPv6 addresses on its interface (using Stateless,
 Stateful address autoconfiguration procedures or manual address
 configuration) from the hosted prefix(es) on that link.  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 from
 the hosted prefix(es) by standard IPv6 mechanisms such as Stateless
 Autoconfiguration [RFC4862] or Privacy extensions [RFC4941].
 When stateful address autoconfiguration is supported on the link, the
 mobile node can obtain the address configuration from the DHCP server
 located in the Proxy Mobile IPv6 domain, by standard DHCP mechanisms,
 as specified in [RFC3315].  The obtained address(es) will be from its
 home network prefix(es).  Section 6.11 specifies the details on how
 this configuration can be achieved.

Gundavelli, et al. Standards Track [Page 44] RFC 5213 Proxy Mobile IPv6 August 2008

 Additionally, other address configuration mechanisms specific to the
 access link between the mobile node and the mobile access gateway may
 also be used for delivering the address configuration to the mobile
 node.  This specification does not modify the behavior of any of the
 standard IPv6 address configuration mechanisms.

6.5. Access Authentication and 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 are 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.

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 and unique across the Proxy Mobile IPv6 domain.  The
 mobility entities in the Proxy Mobile IPv6 domain MUST be able to use
 this identifier in the signaling messages and unambiguously identify
 a given mobile node.  The following are some of the considerations
 related to this MN-Identifier.
 o  The MN-Identifier is typically obtained as part of the access
    authentication or from a notified network attachment event.  In
    cases where the user identifier authenticated during access
    authentication uniquely identifies a mobile node, the MN-
    Identifier MAY be the same as the user identifier.  However, the
    user identifier MUST NOT be used if it identifies a user account
    that can be used from more than one mobile node operating in the
    same Proxy Mobile IPv6 domain.
 o  In some cases, the obtained identifier, as part of the access
    authentication, can be a temporary identifier and further that
    temporary identifier may be different at each re-authentication.
    However, 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 Remote Authentication Dial-In User Service (RADIUS)
    attribute, Chargeable-User-Identifier [RFC4372] may be used, as
    long as it uniquely identifies a mobile node, and not a user
    account that can be used with multiple mobile nodes.

Gundavelli, et al. Standards Track [Page 45] RFC 5213 Proxy Mobile IPv6 August 2008

 o  In some cases and for privacy reasons, 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 does not detect any change with respect to its layer-3
 attachment even after it changes its point of attachment in 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 Advertisement
 messages advertising the mobile node's home network prefix(es)
 carried using the Prefix Information option(s) [RFC4861] and with
 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(es) details from the received Proxy Binding
 Acknowledgement message, or it may obtain them from the mobile node's
 policy profile.  However, the mobile access gateway SHOULD send the
 Router Advertisements advertising the mobile node's home network
 prefix(es) only after successfully completing the binding
 registration with the mobile node's local mobility anchor.
 When advertising the home network prefix(es) in the Router
 Advertisement messages, the mobile access gateway MAY set the prefix
 lifetime value for the advertised prefix(es) 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 does not detect a change of layer-3 attachment.  Every

Gundavelli, et al. Standards Track [Page 46] RFC 5213 Proxy Mobile IPv6 August 2008

 time the mobile node attaches to a new link, the event related to the
 interface state change will trigger the mobile node to perform
 Duplicate Address Detection (DAD) operation on the link-local and
 global address(es).  However, if the mobile node is Detecting Network
 Attachment in IPv6 (DNAv6) enabled, as specified in [DNAV6], it may
 not detect the link change due to DNAv6 optimizations and may not
 trigger the duplicate address detection (DAD) procedure for its
 existing addresses, which may potentially lead to address collisions
 after the mobile node's handoff to a new link.
 The issue of address collision is not relevant to the mobile node's
 global address(es).  Since the assigned home network prefix(es) are
 for the mobile node's exclusive usage, no other node shares an
 address (other than Subnet-Router anycast address that is configured
 by the mobile access gateway) from the prefix(es), and so the
 uniqueness for the mobile node's global address is assured on the
 access link.
 The issue of address collision is however relevant to the mobile
 node's link-local addresses since the mobile access gateway and the
 mobile node will have link-local addresses configured from the same
 link-local prefix (FE80::/64).  This leaves a room for link-local
 address collision between the two neighbors (i.e., the mobile node
 and the mobile access gateway) on that access link.  For solving this
 problem, this specification requires that the link-local address that
 the mobile access gateway configures on the point-to-point link
 shared with a given mobile node be generated by the local mobility
 anchor and be stored in the mobile node's Binding Cache entry.  This
 address will not change for the duration of that mobile node's
 mobility session and can be provided to the serving mobile access
 gateway at every mobile node's handoff, as part of the Proxy Mobile
 IPv6 signaling messages.  The specific method by which the local
 mobility anchor generates the link-local address is out of scope for
 this specification.
 It is highly desirable that the access link on the mobile access
 gateway shared with the mobile node be provisioned in such a way that
 before the mobile node completes the DAD operation [RFC4862] on its
 link-local address, the mobile access gateway on that link is aware
 of its own link-local address provided by the local mobility anchor
 that it needs to use on that access link.  This essentially requires
 a successful completion of the Proxy Mobile IPv6 signaling by the
 mobile access gateway before the mobile node completes the DAD
 operation.  This can be achieved by ensuring that link-layer
 attachment does not complete until the Proxy Mobile IPv6 signaling is

Gundavelli, et al. Standards Track [Page 47] RFC 5213 Proxy Mobile IPv6 August 2008

 completed.  Alternatively, network and local mobility anchor capacity
 and signaling retransmission timers can be provisioned in such a way
 that signaling is likely to complete during the default waiting
 period associated with the DAD process.
 Optionally, implementations MAY choose to configure a fixed link-
 local address across all the access links in a Proxy Mobile IPv6
 domain and without a need for carrying this address from the local
 mobility anchor to the mobile access gateway in the Proxy Mobile IPv6
 signaling messages.  The configuration variable
 FixedMAGLinkLocalAddressOnAllAccessLinks determines the enabled mode
 in that Proxy Mobile IPv6 domain.

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 [RFC4283], carrying the MN-Identifier for
      identifying the mobile node.
 3.   The Home Network Prefix option(s) MUST be present in the Proxy
      Binding Update message.  If the mobile access gateway learns the
      mobile node's home network prefix(es) either from its policy
      store or from other means, the mobile access gateway MAY choose
      to request the local mobility anchor to allocate the specific
      prefix(es) by including a Home Network Prefix option for each of
      those requested prefixes.  The mobile access gateway MAY also
      choose to include just one Home Network Prefix option with the
      prefix value of ALL_ZERO, for requesting the local mobility
      anchor to do the prefix assignment.  However, when including a
      Home Network Prefix option with the prefix value of ALL_ZERO,
      there MUST be only one instance of the Home Network prefix
      option in the request.
 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.

Gundavelli, et al. Standards Track [Page 48] RFC 5213 Proxy Mobile IPv6 August 2008

  • The Handoff Indicator field MUST be set to a value of 1

(Attachment over a new interface) if the mobile access

         gateway determines (under the Handoff Indicator
         considerations specified in this section) that the mobile
         node's current attachment to the network over this interface
         is not as a result of a 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 a value of 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 a handoff of an existing
         mobility session between two different interfaces of the
         mobile node.
  • The Handoff Indicator field MUST be set to a value of 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 a 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 a value of 4

(Handoff state unknown) if the mobile access gateway cannot

         determine if the mobile node's current attachment is due to a
         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.

Gundavelli, et al. Standards Track [Page 49] RFC 5213 Proxy Mobile IPv6 August 2008

  • Some link layers have link-layer identifiers that can be used

to distinguish (a) the movement of a particular interface to

         a new attachment from (b) the attachment of a new interface
         from the same host.  Option value 3 (Handoff between mobile
         access gateways for the same interface) is appropriate in
         case (a) and a value of 1 (Attachment over a new interface)
         in case (b).
  • 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 cannot 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 the link layer exists, the host and the

network would need to inform each other about the intended

         movement.  The 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's mobility session basis as
      specified in [RFC3775] (if the Sequence-Number-based scheme is
      in use) MUST be present.  This can be determined based on the
      value of the configuration flag TimestampBasedApproachInUse.
      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 (maintained at each mobile
      access gateway and not to be confused with the per mobile node
      sequence number specified in [RFC3775]).  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 Link-layer Identifier option carrying the link-
      layer identifier of the currently attached interface MUST be
      present in the Proxy Binding Update message, if the mobile
      access gateway is aware of the same.  If the link-layer
      identifier of the currently attached interface is not known or
      if the identifier value is ALL_ZERO, this option MUST NOT be
      present.

Gundavelli, et al. Standards Track [Page 50] RFC 5213 Proxy Mobile IPv6 August 2008

 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 by which
      the mobile node is currently attached to the mobile access
      gateway.
 9.   The Link-local Address option MUST be present in the Proxy
      Binding Update message only if the value of the configuration
      variable FixedMAGLinkLocalAddressOnAllAccessLinks is set to a
      value of ALL_ZERO; otherwise, the Link-local Address option MUST
      NOT be present in the request.  Considerations from Section 6.8
      MUST be applied when using the Link-local Address option.
  • For querying the local mobility anchor to provide the link-

local address that it should use on the point-to-point link

         shared with the mobile node, this option MUST be set to
         ALL_ZERO value.  This essentially serves as a request to the
         local mobility anchor to provide the link-local address that
         it can use on the access link shared with the mobile node.
 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 message.

6.9.1.2. Receiving Proxy Binding Acknowledgement

 On receiving a Proxy Binding Acknowledgement message (format
 specified in Section 8.2) 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 to value of 1)
      MUST be authenticated as described in Section 4.  When IPsec is
      used for message authentication, the SPI in the IPsec header
      [RFC4306] 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 of [RFC3775] when processing Mobility Headers in the
      received Proxy Binding Acknowledgement message.

Gundavelli, et al. Standards Track [Page 51] RFC 5213 Proxy Mobile IPv6 August 2008

 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
      [RFC3775], related to the presence of a Type 2 Routing header in
      the Proxy Binding Acknowledgement message.
 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 is 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 Link-layer 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.  In this case, the mobile access
      gateway MUST NOT retransmit the Proxy Binding Update message
      until 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 a Proxy Binding Update message again for
      that mobile node until an administrative action is taken.  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.

Gundavelli, et al. Standards Track [Page 52] RFC 5213 Proxy Mobile IPv6 August 2008

 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.
 10.  If the received Proxy Binding Acknowledgement message has the
      Status field value set to NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX
      (The mobile node is not authorized for one or more of the
      requesting home network prefixes), the mobile access gateway
      SHOULD NOT request the same prefix(es) again, but MAY request
      the local mobility anchor to do the assignment of prefix(es) by
      including only one Home Network Prefix option with the prefix
      value set to ALL_ZERO.
 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(es) in
      the Router Advertisement messages sent on that access link and
      MUST deny the mobility service to the mobile node by not
      forwarding any packets received from the mobile node using an
      address from the home network prefix(es).  It MAY also tear down
      the point-to-point link shared with 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 establish a bi-directional tunnel to
      the local mobility anchor (if there is no existing bi-
      directional tunnel to that local mobility anchor).
      Considerations from Section 5.6.1 MUST be applied for managing
      the dynamically created bi-directional tunnel.
 13.  The mobile access gateway MUST set up the route for forwarding
      the packets received from the mobile node using address(es) from
      its home network prefix(es) through the bi-directional setup for
      that mobile node.  The created tunnel and the routing state MUST
      result in the forwarding behavior on the mobile access gateway
      as specified in Section 6.10.5.
 14.  The mobile access gateway MUST also update the Binding Update
      List entry to reflect the accepted binding registration values.
      It MUST also advertise the mobile node's home network prefix(es)
      as the hosted on-link prefixes, by including them in the Router
      Advertisement messages that it sends on that access link.

Gundavelli, et al. Standards Track [Page 53] RFC 5213 Proxy Mobile IPv6 August 2008

 15.  If the received Proxy Binding Acknowledgement message has the
      address in the Link-local Address option set to a NON_ZERO
      value, the mobile access gateway SHOULD configure that link-
      local address on that point-to-point link and SHOULD NOT
      configure any other link-local address without performing a DAD
      operation [RFC4862].  This will avoid any potential link-local
      address collisions on that access link.  However, if the link-
      local address generated by the local mobility anchor happens to
      be already in use by the mobile node on that link, the mobile
      access gateway MUST NOT use that address, but SHOULD configure a
      different link-local address.  It SHOULD also upload this link-
      local address to the local mobility anchor by immediately
      sending a Proxy Binding Update message and by including this
      address in the Link-local Address option.

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 Proxy
     Binding Update message, under the considerations specified in
     Section 6.9.1.1.  However, the following exceptions apply.
 2.  There MUST be a Home Network Prefix option for each of the
     assigned home network prefixes assigned for that mobility session
     and with the prefix value in the option set to that respective
     prefix value.
 3.  The Handoff Indicator field in the Handoff Indicator option MUST
     be set to a value of 5 (Handoff state not changed - Re-
     Registration).

6.9.1.4. Mobile Node Detachment and Binding De-Registration

 1.  If 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
     Proxy Binding Update message, under the considerations specified
     in Section 6.9.1.1.  However, the following exceptions apply.

Gundavelli, et al. Standards Track [Page 54] RFC 5213 Proxy Mobile IPv6 August 2008

 2.  There MUST be a Home Network Prefix option for each of the
     assigned home network prefixes assigned for that mobility session
     and with the prefix value in the option set to the respective
     prefix value.
 3.  The Handoff Indicator field in the Handoff Indicator option MUST
     be set to a value of 4 (Handoff state unknown).
 Either upon receipt of a Proxy Binding Acknowledgement message from
 the local mobility anchor with the Status field set to 0 (Proxy
 Binding Update Accepted), or after INITIAL_BINDACK_TIMEOUT [RFC3775]
 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 remove the created routing state for tunneling the mobile
     node's traffic.
 3.  If there is a dynamically created tunnel to the mobile node's
     local mobility anchor and if there are not other mobile nodes for
     which the tunnel is being used, then the tunnel MUST be deleted.
 4.  It MUST tear down 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.

6.9.1.5. Constructing the Proxy Binding Update Message

 o  The mobile access gateway, when sending the Proxy Binding Update
    message 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 to value 1 */
            Mobility Options
             - Mobile Node Identifier option            (mandatory)
             - Home Network Prefix option(s)            (mandatory)
             - Handoff Indicator option                 (mandatory)
             - Access Technology Type option            (mandatory)
             - Timestamp option                         (optional)
             - Mobile Node Link-layer Identifier option (optional)
             - Link-local Address option                (optional)
              Figure 12: Proxy Binding Update Message Format

Gundavelli, et al. Standards Track [Page 55] RFC 5213 Proxy Mobile IPv6 August 2008

 o  The Source Address field in the IPv6 header of the message MUST be
    set to the global address configured on the egress 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 for this Proxy Binding Update message.
    However, when there is an Alternate Care-of Address option present
    in the request, this address will be not be considered as the
    Proxy-CoA, but the address in the Alternate Care-of Address option
    will be considered as the Proxy-CoA.
 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 [RFC4283] MUST be present.
 o  At least one 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 Link-layer Identifier option MAY be present.
 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 [RFC3775], the Home Address option [RFC3775]
    MUST NOT be present in the IPv6 Destination Options extension
    header of the Proxy Binding Update message.

6.9.2. Router Solicitation Messages

 A mobile node may send a Router Solicitation message on the access
 link shared with the mobile access gateway.  The Router Solicitation
 message that the mobile node sends is as specified in [RFC4861].  The
 mobile access gateway, on receiving the Router Solicitation message
 or before sending a Router Advertisement message, MUST apply the
 following considerations.
 1.  The mobile access gateway, on receiving the Router Solicitation
     message, SHOULD send a Router Advertisement message containing
     the mobile node's home network prefix(es) as the on-link
     prefix(es).  However, before sending the Router Advertisement

Gundavelli, et al. Standards Track [Page 56] RFC 5213 Proxy Mobile IPv6 August 2008

     message containing the mobile node's home network prefix(es), it
     SHOULD complete the binding registration process with the mobile
     node's local mobility anchor.
 2.  If the local mobility anchor rejects the Proxy Binding Update
     message, or, if the mobile access gateway failed to complete the
     binding registration process for whatever reason, the mobile
     access gateway MUST NOT advertise the mobile node's home network
     prefix(es) 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.
 3.  The mobile access gateway SHOULD add the MTU option, as specified
     in [RFC4861], to the Router Advertisement messages that it sends
     on the access link.  This will ensure the mobile node on the link
     uses the advertised MTU value.  The MTU value SHOULD reflect the
     tunnel MTU for the bi-directional tunnel between the mobile
     access gateway and the local mobility anchor.  Considerations
     from Section 6.9.5 SHOULD be applied for determining the tunnel
     MTU value.

6.9.3. Default-Router

 In Proxy Mobile IPv6, the mobile access gateway is the IPv6 default-
 router for the mobile node 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
 Advertisement messages.  If these Router Advertisements are sent
 using a different link-local address or a different link-layer
 address, the mobile node will always detect a new default-router
 after every handoff.  For solving this problem, this specification
 requires all the mobile access gateways in the Proxy Mobile IPv6
 domain to use the same link-local and link-layer address on any of
 the access links wherever the mobile node attaches.  These addresses
 can be fixed addresses across the entire Proxy Mobile IPv6 domain,
 and all the mobile access gateways can use these globally fixed
 address on any of the point-to-point links.  The configuration
 variables FixedMAGLinkLocalAddressOnAllAccessLinks and
 FixedMAGLinkLayerAddressOnAllAccessLinks SHOULD be used for this
 purpose.  Additionally, this specification allows the local mobility
 anchor to generate the link-local address and provide it to the
 mobile access gateway as part of the signaling messages.
 However, both of these approaches (a link-local address generated by
 the local mobility anchor or when using a globally fixed link-local
 address) have implications on the deployment of SEcure Neighbor
 Discovery (SEND) [RFC3971].  In SEND, routers have certificates and

Gundavelli, et al. Standards Track [Page 57] RFC 5213 Proxy Mobile IPv6 August 2008

 public key pairs, and their Router Advertisements are signed with the
 private keys of these key pairs.  When a number of different routers
 use the same addresses, the routers either all have to be able to
 construct these signatures for the same key pair, or the used key
 pair and the router's cryptographic identity must change after a
 movement.  Both approaches are problematic.  Sharing of private key
 information across multiple nodes in a PMIP6 domain is poor design
 from a security perspective.  And changing even the cryptographic
 identity of the router goes against the general idea of the Proxy
 Mobile IPv6 being as invisible to the hosts as possible.
 There is, however, ongoing work in the IETF to revise the SEND
 specifications.  It is suggested that these revisions also address
 the above problem.  Other revisions are needed to deal with other
 problematic cases (such as Neighbor Discovery proxies) before wide-
 spread deployment of SEND.

6.9.4. Retransmissions and Rate Limiting

 The mobile access gateway is responsible for retransmissions and rate
 limiting the Proxy Binding Update messages that it sends to the local
 mobility anchor.  The Retransmission and the Rate Limiting rules are
 as specified in [RFC3775].  However, the following considerations
 MUST be applied.
 1.  When the mobile access gateway sends a Proxy Binding Update
     message, it should use the constant, INITIAL_BINDACK_TIMEOUT
     [RFC3775], for configuring the retransmission timer, as specified
     in Section 11.8 [RFC3775].  However, the mobile access gateway is
     not required to use a longer retransmission interval of
     InitialBindackTimeoutFirstReg, as specified in [RFC3775], for the
     initial Proxy Binding Update message.
 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 of [RFC3775], 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 [RFC3775].  The mobile access gateway
     MAY continue to send these messages at this slower rate
     indefinitely.

Gundavelli, et al. Standards Track [Page 58] RFC 5213 Proxy Mobile IPv6 August 2008

 4.  If the Timestamp-based scheme is in use, the retransmitted Proxy
     Binding Update messages MUST use the latest timestamp.  If the
     Sequence Number scheme is in use, the retransmitted Proxy Binding
     Update messages MUST use a Sequence Number value greater than
     that was used for the previous transmission of this Proxy Binding
     Update message, just as specified in [RFC3775].

6.9.5. Path MTU Discovery

 It is important that mobile node, mobile access gateway, and local
 mobility anchor have a correct understanding of MTUs.  When the
 mobile node uses the correct MTU, it can send packets that do not
 exceed the local link MTU and do not cause the tunneled packets from
 the mobile access gateway to be fragmented.  This is important both
 from the perspective of efficiency, as well as preventing hard-to-
 diagnose MTU problems.  The following are some of the considerations
 related to Path MTU discovery.
 o  The local mobility anchor and mobile access gateway MAY use the
    Path MTU discovery mechanisms, as specified in [RFC1981] or in
    [RFC4821], for determining the Path MTU (PMTU) for the (LMA-MAG)
    paths.  The specific discovery mechanism to be used in a given
    deployment can be configurable.
 o  The mobility entities MUST implement and SHOULD support ICMP-based
    Path MTU discovery mechanism, as specified in [RFC1981].  However,
    this mechanism may not work correctly if the Proxy Mobile IPv6
    network does not deliver or process ICMP Packet Too Big messages.
 o  The mobility entities MAY implement Packetization Layer Path MTU
    discovery mechanisms, as specified in [RFC4821], and use any
    application traffic as a payload for the PMTU discovery.  Neither
    the Proxy Mobile IPv6 protocol or the tunnel between the mobile
    access gateway and local mobility agent can easily be used for
    this purpose.  However, implementations SHOULD support at least
    the use of an explicit ICMP Echo Request/Response for this
    purpose.
 o  The mobility entities MAY choose to perform Path MTU discovery for
    all the (LMA-MAG) paths at the boot time and may repeat this
    operation periodically to ensure the Path MTU values have not
    changed for those paths.  If the dynamic PMTU discovery mechanisms
    fail to determine the Path MTU, an administratively configured
    default value MUST be used.

Gundavelli, et al. Standards Track [Page 59] RFC 5213 Proxy Mobile IPv6 August 2008

 o  The IPv6 tunnel MTU for an established tunnel between the local
    mobility anchor and the mobile access gateway MUST be computed
    based on the determined Path MTU value for that specific path and
    the computation should be as specified in Section 6.7 of
    [RFC2473].
 o  The mobile access gateway SHOULD use the determined tunnel Path
    MTU value (for the tunnel established with the mobile node's local
    mobility anchor) as the MTU value in the MTU option that it sends
    in the Router Advertisements on the access link shared with the
    mobile node.  But, if the MTU value of the access link shared with
    the mobile node is lower than the determined Path MTU value, then
    the MTU of the access link MUST be used in the MTU option.
 o  If the mobile access gateway detects a change in the MTU value for
    any of the paths (LMA-MAG) and at any point of time, the
    corresponding tunnel MTU value MUST be updated to reflect the
    change in Path MTU value.  The adjusted tunnel MTU value (lower of
    the Path MTU and the access link MTU) SHOULD be notified to the
    impacted mobile nodes by sending additional Router Advertisement
    messages.  Additionally, the adjusted tunnel MTU value MUST be
    used in all the subsequent Router Advertisement messages as well.

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
 interfaces.
               Proxy-CoA                   LMAA
                  |                          |
  +--+          +---+                      +---+          +--+
  |MN|----------|MAG|======================|LMA|----------|CN|
  +--+          +---+                      +---+          +--+
                          IPv6 Tunnel
                  Figure 13: Proxy Mobile IPv6 Tunnel

6.10.1. Transport Network

 As per this specification, the transport network between the local
 mobility anchor and the mobile access gateway is an IPv6 network.
 The document [IPV4-PMIP6] specifies the required extensions for
 negotiating IPv4 transport and the corresponding encapsulation mode.

Gundavelli, et al. Standards Track [Page 60] RFC 5213 Proxy Mobile IPv6 August 2008

6.10.2. Tunneling and Encapsulation Modes

 An IPv6 address that a mobile node uses from its home network
 prefix(es) 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 [RFC3775]
 defines the use of IPv6-over-IPv6 tunneling [RFC2473] between the
 home agent and the mobile node, and this specification extends the
 use of the same tunneling mechanism for use between the local
 mobility anchor and the mobile access gateway.
 On most operating systems, a tunnel is implemented as a virtual
 point-to-point interface.  The source and the destination address of
 the two endpoints 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 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 a global address on its egress interface
 (Proxy-CoA) and the destination address field set to the global
 address of the local mobility anchor (LMAA).
 The following is the supported packet encapsulation mode 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
    [RFC2473].
 The companion document [IPV4-PMIP6] specifies other encapsulation
 modes for supporting IPv4 transport.
 o  IPv6-In-IPv4 - IPv6 datagram encapsulation in an IPv4 packet.  The
    details on how this mode is negotiated are specified in
    [IPV4-PMIP6].
 o  IPv6-In-IPv4-UDP - IPv6 datagram encapsulation in an IPv4 UDP
    packet.  This mode is specified in [IPV4-PMIP6].
 o  IPv6-In-IPv4-UDP-TLV - IPv6 datagram encapsulation in an IPv4 UDP
    packet with a TLV header.  This mode is specified in [IPV4-PMIP6].

Gundavelli, et al. Standards Track [Page 61] RFC 5213 Proxy Mobile IPv6 August 2008

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 flag EnableMAGLocalRouting MAY be used for controlling
 this behavior.  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.  Considerations from
    [RFC2473] MUST be applied for IPv6 decapsulation.  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 an ICMP
    control message, the considerations from [RFC2473] MUST be
    applied.
 o  On receiving a packet from a correspondent node that is connected
    to the mobile access gateway as a regular IPv6 host (see Section
    6.14) destined to a mobile node that is also locally attached, the
    mobile access gateway MUST check the flag EnableMAGLocalRouting to
    determine if the packet can be delivered directly to the mobile
    node.  If the mobile access gateway is not allowed to route the

Gundavelli, et al. Standards Track [Page 62] RFC 5213 Proxy Mobile IPv6 August 2008

    packet directly, it MUST route the packet towards the local
    mobility anchor where the destination address is topologically
    anchored, else 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
    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 for a destination that is locally connected, the mobile
    access gateway MUST check the flag 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 MUST route
    the packet directly to the destination.
 o  On receiving a packet from a 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.
 o  The format of the tunneled packet is shown below.  Considerations
    from [RFC2473] MUST be applied for IPv6 encapsulation.  However,
    when using IPv4 transport, the format of the tunneled packet is as
    described in [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 14: Tunneled Packet from MAG to LMA
 o  The format of the tunneled packet is shown below, when payload
    protection using IPsec is enabled for the mobile node's data
    traffic.  However, when using IPv4 transport, the format of the
    packet is as described in [IPV4-PMIP6].

Gundavelli, et al. Standards Track [Page 63] RFC 5213 Proxy Mobile IPv6 August 2008

      IPv6 header (src= Proxy-CoA, dst= LMAA     /* Tunnel Header */
         ESP Header in tunnel mode               /* ESP Header */
            IPv6 header (src= MN-HoA, dst= CN )  /* Packet Header */
               Upper layer protocols             /* Packet Content*/
    Figure 15: Tunneled Packet from MAG to LMA with Payload Protection

6.11. Supporting DHCP-Based Address Configuration on the Access Link

 This section explains how Stateful Address Configuration using DHCP
 support can be enabled in a Proxy Mobile IPv6 domain.  It also
 identifies the required configuration in DHCP and mobility
 infrastructures for supporting this address configuration mode and
 also identifies the protocol interactions between these two systems.
 o  For supporting Stateful Address Configuration using DHCP, the DHCP
    relay agent [RFC3315] service MUST be supported on all the mobile
    access gateways in the Proxy Mobile IPv6 domain.  Further, as
    specified in Section 20 of [RFC3315], the DHCP relay agent should
    be configured to use a list of destination addresses, which MAY
    include unicast addresses, the All_DHCP_Servers multicast address,
    or other addresses as required in a given deployment.
 o  The DHCP infrastructure needs to be configured to assign addresses
    from each of the prefixes assigned to a link in that Proxy Mobile
    IPv6 domain.  The DHCP relay agent indicates the link to which the
    mobile node is attached by including an IPv6 address from any of
    the prefixes assigned to that link in the link-address field of
    the Relay Forward message.  Therefore, for each link in the Mobile
    IPv6 domain, the DHCP infrastructure will:
  • be configured with a list of all of the prefixes associated

with that link;

  • identify the link to which the mobile node is attached by

looking up the prefix for the link-address field in the Relay

       Forward message in the list of prefixes associated with each
       link;
  • assign to the host an address from each prefix associated with

the link to which the mobile node is attached.

    This DHCP infrastructure configuration requirement is identical to
    other IPv6 networks; other than receiving DHCP messages from a
    mobile node through different relay agents (MAGs) over time, the
    DHCP infrastructure will be unaware of the mobile node's
    capability with respect to mobility support.

Gundavelli, et al. Standards Track [Page 64] RFC 5213 Proxy Mobile IPv6 August 2008

 o  The local mobility anchor needs to have the same awareness with
    respect to the links along with the associated prefixes in a Proxy
    Mobile IPv6 domain.  When a local mobility anchor assigns
    prefix(es) to a mobile node, it MUST assign all the prefixes
    associated with a given link and all of those assigned prefixes
    will remain as the home network prefixes for that mobile node
    throughout the life of that mobility session.  The serving mobile
    access gateway that hosts these prefixes is physically connected
    to that link and can function as the DHCP relay agent.  This
    common understanding between DHCP and mobility entities about all
    the links in the domain along with the associated prefixes
    provides the required coordination for allowing mobility entities
    to perform prefix assignment dynamically to a mobile node and
    still allow the DHCP infrastructure to perform address assignment
    for that mobile node only from its home network prefixes.
 o  When a mobile node sends a DHCP request message, the DHCP relay
    agent function on the mobile access gateway will set the link-
    address field in the DHCP message to an address in the mobile
    node's home network prefix (any one of the mobile node's home
    network prefixes assigned to that mobile node's attached
    interface).  The mobile access gateway can generate an
    autoconfiguration address from one of the mobile node's home
    network prefixes [RFC4862] and can use this address link-address
    option, so as to provide a hint to the DHCP Server for the link
    identification.  The DHCP server, on receiving the request from
    the mobile node, will allocate addresses from all the prefixes
    associated with that link (identified using the link-address field
    of the request).
 o  Once the mobile node obtains address(es), moves to a different
    link, and sends a DHCP request (at any time) for extending the
    DHCP lease, the DHCP relay agent on the new link will set the
    link-address field in the DHCP Relay Forward message to one of the
    mobile node's home network prefixes.  The DHCP server will
    identify the client from the Client-DUID option and will identify
    the link from the link-address option present in the request and
    will allocate the same address(es) as before.
 o  For correct operation of the model of network-based mobility
    management in which the host does not participate in any mobility
    management, the mobile node MUST always be assigned an identical
    set of IPv6 addresses regardless of the access link to which the
    mobile node is attached.  For example, the mobile access gateways

Gundavelli, et al. Standards Track [Page 65] RFC 5213 Proxy Mobile IPv6 August 2008

    in the Proxy Mobile IPv6 domain should be configured so that DHCP
    messages from a mobile node will always be handled by the same
    DHCP server or by a server from the same group of coordinated DHCP
    servers serving that domain.  DHCP-based address configuration is
    not recommended for deployments in which the local mobility anchor
    and the mobile access gateway are located in different
    administrative domains.

6.12. Home Network Prefix Renumbering

 If the mobile node's home network prefix(es) gets renumbered or
 becomes invalid during the middle of a mobility session, the mobile
 access gateway MUST withdraw the prefix(es) by sending a Router
 Advertisement message on the access link with zero prefix lifetime
 for the prefix(es) that is being renumbered.  Also, the local
 mobility anchor and the mobile access gateway MUST delete the created
 routing state for the renumbered prefix(es).  However, the specific
 details on how the local mobility anchor notifies the mobile access
 gateway about the mobile node's home network prefix(es) 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 a 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:

Gundavelli, et al. Standards Track [Page 66] RFC 5213 Proxy Mobile IPv6 August 2008

 o  Link-layer event specific to the access technology
 o  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
 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
 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 to network-based mobility
 management service, then the mobile access gateway must ensure the
 mobile node does not detect any change with respect to its layer-3
 attachment, as explained in various sections of this specification.
 If the mobile node is not entitled to 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 a scenario, the normal IPv6 considerations
 apply.  If IPv6 access is enabled, the mobile node SHOULD be able to
 obtain IPv6 address(es) using the normal IPv6 address configuration
 procedures.  The obtained address(es) must be from a local visitor
 network prefix(es).  This essentially ensures that the mobile access
 gateway functions as a normal access router to a mobile node attached
 to its access link and without 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

Gundavelli, et al. Standards Track [Page 67] RFC 5213 Proxy Mobile IPv6 August 2008

 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 set up the forwarding for
 the mobile node's data traffic.
 When a mobile node attaches to the access link, it will typically
 send a Router Solicitation message [RFC4861].  The mobile access
 gateway on the access link will respond to the Router Solicitation
 message with a Router Advertisement message.  The Router
 Advertisement message will carry the mobile node's home network
 prefix(es), 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 completes the
 signaling with the mobile node's local mobility anchor, the mobile
 access gateway may not know the mobile node's home network prefix(es)
 and may not be able to emulate the mobile node's home link on the
 access link.  In such a scenario, the mobile node may notice a delay
 before it receives a Router Advertisement message.  This will also
 affect mobile nodes that would be capable of handling their own
 mobility, or mobile nodes that do not need to maintain the same IP
 address through movements.
 If the received Router Advertisement message has the Managed Address
 Configuration flag set, the mobile node, as it would normally do,
 will send a DHCP Request [RFC3315].  The DHCP relay service enabled
 on that access link will ensure the mobile node can obtain one or
 more addresses from its home network prefix(es).
 If the received Router Advertisement message does not have the
 Managed Address Configuration flag set and if the mobile node is
 allowed to use autoconfigured address(es), the mobile node will be
 able to obtain IPv6 address(es) from each of its home network
 prefixes using any of the standard IPv6 address configuration
 mechanisms permitted for that mode.
 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 [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.

Gundavelli, et al. Standards Track [Page 68] RFC 5213 Proxy Mobile IPv6 August 2008

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
 link is in the scope of that Proxy Mobile IPv6 domain, the mobile
 node will always detect the same router advertising itself as a
 default-router and advertising the mobile node's home network
 prefix(es) on each connected link.  If the mobile node has address
 configuration that it obtained using DHCP, it will be able to retain
 the address configuration and extend the lease lifetime.

8. Message Formats

 This section defines extensions to the Mobile IPv6 [RFC3775] protocol
 messages.

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 [RFC3775] and with the additional (R) and (M) flags, as
 specified in [RFC3963] and [RFC4140], respectively.

Gundavelli, et al. Standards Track [Page 69] RFC 5213 Proxy Mobile IPv6 August 2008

 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 of
    [RFC3775].  The local mobility anchor MUST ignore and skip any
    options that it does not understand.
    As per this specification, the following mobility options are
    valid in a Proxy Binding Update message.  These options can be
    present in the message in any order.  There can be one or more
    instances of the Home Network Prefix options present in the
    message.  However, there cannot be more than one instance of any
    of the following options.
       Mobile Node Identifier option
       Home Network Prefix option
       Handoff Indicator option
       Access Technology Type option
       Timestamp option
       Mobile Node Link-layer Identifier option
       Link-local Address option
    Additionally, there can be one or more instances of the Vendor-
    Specific Mobility option [RFC5094].
 For descriptions of other fields present in this message, refer to
 Section 6.1.7 of [RFC3775].

Gundavelli, et al. Standards Track [Page 70] RFC 5213 Proxy Mobile IPv6 August 2008

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
 [RFC3775] and with the additional (R) flag as specified in [RFC3963].
 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 to a value of 1 only if the
    corresponding Proxy Binding Update had the Proxy Registration Flag
    (P) set to value of 1.
 Mobility Options
    A 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 of
    [RFC3775].  The mobile access gateway MUST ignore and skip any
    options that it does not understand.
    As per this specification, the following mobility options are
    valid in a Proxy Binding Acknowledgement message.  These options
    can be present in the message in any order.  There can be one or

Gundavelli, et al. Standards Track [Page 71] RFC 5213 Proxy Mobile IPv6 August 2008

    more instances of the Home Network Prefix options present in the
    message.  However, there cannot be more than one instance of any
    of the following options.
       Mobile Node Identifier option
       Home Network Prefix option
       Handoff Indicator option
       Access Technology Type option
       Timestamp option
       Mobile Node Link-layer Identifier option
       Link-local Address option
    Additionally, there can be one or more instances of the Vendor-
    Specific Mobility option [RFC5094].
 Status
    An 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
    Proxy Binding Update message 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
 Section 6.1.8 of [RFC3775].

8.3. Home Network Prefix Option

 A new option, Home Network Prefix option is defined for use with 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.  There can be multiple Home Network
 Prefix options present in the message.
 The Home Network Prefix Option has an alignment requirement of 8n+4.
 Its format is as follows:

Gundavelli, et al. Standards Track [Page 72] RFC 5213 Proxy Mobile IPv6 August 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
         22
     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 use with 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, et al. Standards Track [Page 73] RFC 5213 Proxy Mobile IPv6 August 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
      23
  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)
      An 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 defined.
      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 use with
 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 by which the mobile node is currently attached to the
 mobile access gateway.

Gundavelli, et al. Standards Track [Page 74] RFC 5213 Proxy Mobile IPv6 August 2008

 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
      24
  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)
      An 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         ("Reserved")
      1: Virtual          ("Logical Network Interface")
      2: PPP              ("Point-to-Point Protocol")
      3: IEEE 802.3       ("Ethernet")
      4: IEEE 802.11a/b/g ("Wireless LAN")
      5: IEEE 802.16e     ("WIMAX")

Gundavelli, et al. Standards Track [Page 75] RFC 5213 Proxy Mobile IPv6 August 2008

8.6. Mobile Node Link-layer Identifier Option

 A new option, Mobile Node Link-layer Identifier option is defined for
 use with 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-layer identifier.
 The format of the Link-layer Identifier option is shown below.  Based
 on the size of the identifier, the option MUST be aligned
 appropriately, as per mobility option alignment requirements
 specified in [RFC3775].
   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             |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                                                               |
  +                        Link-layer Identifier                  +
  .                              ...                              .
  |                                                               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Type
       25
   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.
   Link-layer Identifier
       A variable length field containing the mobile node's link-layer
       identifier.
       The content and format of this field (including byte and bit
       ordering) is as specified in Section 4.6 of [RFC4861] for
       carrying link-layer addresses.  On certain access links, where
       the link-layer address is not used or cannot be determined,
       this option cannot be used.

Gundavelli, et al. Standards Track [Page 76] RFC 5213 Proxy Mobile IPv6 August 2008

8.7. Link-local Address Option

 A new option, Link-local Address option is defined for use with 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 link-local address
 of the mobile access gateway.
 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
         26
     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 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.
 The Timestamp option has an alignment requirement of 8n+2.  Its
 format is as follows:

Gundavelli, et al. Standards Track [Page 77] RFC 5213 Proxy Mobile IPv6 August 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      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                          Timestamp                            +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    Type
        27
    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 messages.  These values are to be
 allocated from the same number space, as defined in Section 6.1.8 of
 [RFC3775].
 Status values less than 128 indicate that the Proxy Binding Update
 message 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.
 PROXY_REG_NOT_ENABLED: 152
    Proxy registration not enabled for the mobile node

Gundavelli, et al. Standards Track [Page 78] RFC 5213 Proxy Mobile IPv6 August 2008

 NOT_LMA_FOR_THIS_MOBILE_NODE: 153
    Not local mobility anchor for this mobile node
 MAG_NOT_AUTHORIZED_FOR_PROXY_REG: 154
    The mobile access gateway is not authorized to send proxy binding
    updates
 NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX: 155
    The mobile node is not authorized for one or more of the
    requesting home network prefixes
 TIMESTAMP_MISMATCH: 156
    Invalid timestamp value (the clocks are out of sync)
 TIMESTAMP_LOWER_THAN_PREV_ACCEPTED: 157
    The timestamp value is lower than the previously accepted value
 MISSING_HOME_NETWORK_PREFIX_OPTION: 158
    Missing home network prefix option
 BCE_PBU_PREFIX_SET_DO_NOT_MATCH: 159
    All the home network prefixes listed in the BCE do not match all
    the prefixes in the received PBU
 MISSING_MN_IDENTIFIER_OPTION: 160
    Missing mobile node identifier option
 MISSING_HANDOFF_INDICATOR_OPTION: 161
    Missing handoff indicator option
 MISSING_ACCESS_TECH_TYPE_OPTION: 162
    Missing access technology type option

Gundavelli, et al. Standards Track [Page 79] RFC 5213 Proxy Mobile IPv6 August 2008

 Additionally, the following Status values defined in [RFC3775] can
 also be used in a Proxy Binding Acknowledgement message.
    0 Proxy Binding Update accepted
    128 Reason unspecified
    129 Administratively prohibited
    130 Insufficient resources

9. Protocol Configuration Variables

9.1. Local Mobility Anchor - Configuration Variables

 The local mobility anchor MUST allow the following variables to be
 configured by the system management.  The configured values for these
 protocol variables MUST survive server reboots and service restarts.
 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 a
    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.

Gundavelli, et al. Standards Track [Page 80] RFC 5213 Proxy Mobile IPv6 August 2008

 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.
    The default value for this variable is 1500 milliseconds.
    Note that there is a dependency between this value and the values
    used in the retransmission algorithm for Proxy Binding Updates.
    The retransmissions need to happen before
    MaxDelayBeforeNewBCEAssign runs out, as otherwise there are
    situations where a de-registration from a previous mobile access
    gateway may be lost, and the local mobility anchor creates,
    needlessly, a new mobility session and new prefixes for the mobile
    node.  However, this affects situations where there is no
    information from the lower layers about the type of a handoff or
    other parameters that can be used for identifying the mobility
    session.
 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.

9.2. Mobile Access Gateway - Configuration Variables

 The mobile access gateway MUST allow the following variables to be
 configured by the system management.  The configured values for these
 protocol variables MUST survive server reboots and service restarts.
 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.

Gundavelli, et al. Standards Track [Page 81] RFC 5213 Proxy Mobile IPv6 August 2008

    The default value for this flag is set to a value of 0, 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 a value of 1, 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.

9.3. Proxy Mobile IPv6 Domain - Configuration Variables

 All the mobile entities (local mobility anchors and mobile access
 gateways) in a Proxy Mobile IPv6 domain MUST allow the following
 variables to be configured by the system management.  The configured
 values for these protocol variables MUST survive server reboots and
 service restarts.  These variables MUST be globally fixed for a given
 Proxy Mobile IPv6 domain resulting in the same values being enforced
 on all the mobility entities in that domain.
 TimestampBasedApproachInUse
    This flag indicates whether or not the timestamp-based approach
    for message ordering is in use in that Proxy Mobile IPv6 domain.
    When the value for this flag is set to 1, all the mobile access
    gateways in that Proxy Mobile IPv6 domain MUST apply the
    timestamp-based considerations listed in Section 5.5.  When the
    value of this flag is set to 0, sequence-number-based
    considerations listed in Section 5.5 MUST be applied.  The default
    value for this flag is set to value of 1, indicating that the
    timestamp-based mechanism is in use in that Proxy Mobile IPv6
    domain.
 MobileNodeGeneratedTimestampInUse
    This flag indicates whether or not the mobile-node-generated
    timestamp approach is in use in that Proxy Mobile IPv6 domain.
    When the value for this flag is set to 1, the local mobility
    anchors and mobile access gateways in that Proxy Mobile IPv6
    domain MUST apply the mobile node generated timestamp
    considerations as specified in Section 5.5.
    This flag is relevant only when timestamp-based approach is in
    use.  The value for this flag MUST NOT be set to value of 1, if
    the value of the TimestampBasedApproachInUse flag is set to 0.

Gundavelli, et al. Standards Track [Page 82] RFC 5213 Proxy Mobile IPv6 August 2008

    The default value for this flag is set to value of 0, indicating
    that the mobile node generated timestamp mechanism is not in use
    in that Proxy Mobile IPv6 domain.
 FixedMAGLinkLocalAddressOnAllAccessLinks
    This variable indicates the link-local address value that all the
    mobile access gateways SHOULD use on any of the access links
    shared with any of the mobile nodes in that Proxy Mobile IPv6
    domain.  If this variable is initialized to ALL_ZERO value, it
    implies the use of fixed link-local address mode is not enabled
    for that Proxy Mobile IPv6 domain.
 FixedMAGLinkLayerAddressOnAllAccessLinks
    This variable indicates the link-layer address value that all the
    mobile access gateways SHOULD use on any of the access links
    shared with any of the mobile nodes in that Proxy Mobile IPv6
    domain.  For access technologies where there is no link-layer
    address, this variable MUST be initialized to ALL_ZERO value.

10. IANA Considerations

 This document defines six new Mobility Header options, the Home
 Network Prefix Option, Handoff Indicator Option, Access Technology
 Type Option, Mobile Node Link-layer Identifier Option, Link-local
 Address Option, and Timestamp Option.  These options are described in
 Section 8.  The Type value for these options has been assigned from
 the same numbering space as allocated for the other mobility options,
 as defined in [RFC3775].
 The Handoff Indicator Option, defined in Section 8.4 of this
 document, introduces a new Handoff Indicator (HI) numbering space,
 where the values from 0 to 5 have been reserved by this document.
 Approval of new Handoff Indicator type values are to be made through
 IANA Expert Review.
 The Access Technology Type Option, defined in Section 8.5 of this
 document, introduces a new Access Technology type (ATT) numbering
 space, where the values from 0 to 5 have been reserved by this
 document.  Approval of new Access Technology type values 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 [RFC3775].  The allocated values for each of these
 status values must be greater than 128.

Gundavelli, et al. Standards Track [Page 83] RFC 5213 Proxy Mobile IPv6 August 2008

 This document creates a new registry for the flags in the Binding
 Update message called the "Binding Update Flags".
 The following flags are reserved:
    (A) 0x8000 [RFC3775]
    (H) 0x4000 [RFC3775]
    (L) 0x2000 [RFC3775]
    (K) 0x1000 [RFC3775]
    (M) 0x0800 [RFC4140]
    (R) 0x0400 [RFC3963]
 This document reserves a new flag (P) as follows:
    (P) 0x0200
 The rest of the values in the 16-bit field are reserved.  New values
 can be assigned by Standards Action or IESG approval.
 This document also creates a new registry for the flags in the
 Binding Acknowledgment message called the "Binding Acknowledgment
 Flags".  The following values are reserved.
    (K) 0x80 [RFC3775]
    (R) 0x40 [RFC3963]
 This document reserves a new flag (P) as follows:
    (P) 0x20
 The rest of the values in the 8-bit field are reserved.  New values
 can be assigned by Standards Action or IESG approval.

11. Security Considerations

 The potential security threats against any network-based mobility
 management protocol are described in [RFC4832].  This section
 explains how Proxy Mobile IPv6 protocol defends itself against those
 threats.

Gundavelli, et al. Standards Track [Page 84] RFC 5213 Proxy Mobile IPv6 August 2008

 Proxy Mobile IPv6 protocol recommends 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 mobility 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 Proxy Binding Update 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.
 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
 attached to the mobile access gateway that sent the Proxy Binding
 Update message.  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 Jari Arkko, Julien
 Laganier, Christian Vogt, Dave Thaler, Pasi Eronen, Pete McCann,
 Brian Haley, Ahmad Muhanna, JinHyeock Choi, and Elwyn Davies for
 their thorough reviews of this document.
 The authors would also like to thank Alex Petrescu, Alice Qinxia,
 Alper Yegin, Ashutosh Dutta, Behcet Sarikaya, Charles Perkins,
 Domagoj Premec, Fred Templin, Genadi Velev, George Tsirtsis, Gerardo
 Giaretta, Henrik Levkowetz, Hesham Soliman, James Kempf, Jean-Michel

Gundavelli, et al. Standards Track [Page 85] RFC 5213 Proxy Mobile IPv6 August 2008

 Combes, John Jason Brzozowski, Jun Awano, John Zhao, Jong-Hyouk Lee,
 Jonne Soininen, Jouni Korhonen, Kalin Getov, Kilian Weniger, Lars
 Eggert, Magnus Westerlund, Marco Liebsch, Mohamed Khalil, Nishida
 Katsutoshi, Pierrick Seite, Phil Roberts, Ralph Droms, Ryuji
 Wakikawa, Sangjin Jeong, Suresh Krishnan, Tero Kauppinen, Uri
 Blumenthal, 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 document
 to the current form and we acknowledge that!
 The authors would also like to thank Ole Troan, Akiko Hattori, Parviz
 Yegani, Mark Grayson, Michael Hammer, Vojislav Vucetic, Jay Iyer, Tim
 Stammers, Bernie Volz, and Josh Littlefield for their input on this
 document.

13. References

13.1. Normative References

 [RFC2119]     Bradner, S., "Key words for use in RFCs to Indicate
               Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2473]     Conta, A. and S. Deering, "Generic Packet Tunneling in
               IPv6 Specification", RFC 2473, December 1998.
 [RFC3168]     Ramakrishnan, K., Floyd, S., and D. Black, "The
               Addition of Explicit Congestion Notification (ECN) to
               IP", RFC 3168, September 2001.
 [RFC3315]     Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
               and M. Carney, "Dynamic Host Configuration Protocol for
               IPv6 (DHCPv6)", RFC 3315, July 2003.
 [RFC3775]     Johnson, D., Perkins, C., and J. Arkko, "Mobility
               Support in IPv6", RFC 3775, June 2004.
 [RFC4282]     Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The
               Network Access Identifier", RFC 4282, December 2005.
 [RFC4283]     Patel, A., Leung, K., Khalil, M., Akhtar, H., and K.
               Chowdhury, "Mobile Node Identifier Option for Mobile
               IPv6 (MIPv6)", RFC 4283, November 2005.
 [RFC4291]     Hinden, R. and S. Deering, "IP Version 6 Addressing
               Architecture", RFC 4291, February 2006.

Gundavelli, et al. Standards Track [Page 86] RFC 5213 Proxy Mobile IPv6 August 2008

 [RFC4301]     Kent, S. and K. Seo, "Security Architecture for the
               Internet Protocol", RFC 4301, December 2005.
 [RFC4303]     Kent, S., "IP Encapsulating Security Payload (ESP)",
               RFC 4303, December 2005.
 [RFC4861]     Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
               "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
               September 2007.

13.2. Informative References

 [RFC1981]     McCann, J., Deering, S., and J. Mogul, "Path MTU
               Discovery for IP version 6", RFC 1981, August 1996.
 [RFC2865]     Rigney, C., Willens, S., Rubens, A., and W. Simpson,
               "Remote Authentication Dial In User Service (RADIUS)",
               RFC 2865, June 2000.
 [RFC3588]     Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and
               J. Arkko, "Diameter Base Protocol", RFC 3588,
               September 2003.
 [RFC3963]     Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
               Thubert, "Network Mobility (NEMO) Basic Support
               Protocol", RFC 3963, January 2005.
 [RFC3971]     Arkko, J., Kempf, J., Zill, B., and P. Nikander,
               "SEcure Neighbor Discovery (SEND)", RFC 3971,
               March 2005.
 [RFC4140]     Soliman, H., Castelluccia, C., El Malki, K., and L.
               Bellier, "Hierarchical Mobile IPv6 Mobility Management
               (HMIPv6)", RFC 4140, August 2005.
 [RFC4306]     Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
               RFC 4306, December 2005.
 [RFC4330]     Mills, D., "Simple Network Time Protocol (SNTP) Version
               4 for IPv4, IPv6 and OSI", RFC 4330, January 2006.
 [RFC4372]     Adrangi, F., Lior, A., Korhonen, J., and J. Loughney,
               "Chargeable User Identity", RFC 4372, January 2006.
 [RFC4821]     Mathis, M. and J. Heffner, "Packetization Layer Path
               MTU Discovery", RFC 4821, March 2007.

Gundavelli, et al. Standards Track [Page 87] RFC 5213 Proxy Mobile IPv6 August 2008

 [RFC4830]     Kempf, J., "Problem Statement for Network-Based
               Localized Mobility Management (NETLMM)", RFC 4830,
               April 2007.
 [RFC4831]     Kempf, J., "Goals for Network-Based Localized Mobility
               Management (NETLMM)", RFC 4831, April 2007.
 [RFC4832]     Vogt, C. and J. Kempf, "Security Threats to Network-
               Based Localized Mobility Management (NETLMM)",
               RFC 4832, April 2007.
 [RFC4862]     Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
               Address Autoconfiguration", RFC 4862, September 2007.
 [RFC4941]     Narten, T., Draves, R., and S. Krishnan, "Privacy
               Extensions for Stateless Address Autoconfiguration in
               IPv6", RFC 4941, September 2007.
 [RFC5094]     Devarapalli, V., Patel, A., and K. Leung, "Mobile IPv6
               Vendor Specific Option", RFC 5094, December 2007.
 [IPV4-PMIP6]  Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
               Mobile IPv6", Work in Progress, May 2008.
 [DNAV6]       Narayanan, S., Ed., "Detecting Network Attachment in
               IPv6 Networks (DNAv6)", Work in Progress,
               February 2008.

Gundavelli, et al. Standards Track [Page 88] RFC 5213 Proxy Mobile IPv6 August 2008

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(es) on a per-interface basis,
 permitted address configuration modes, roaming policy, and other
 parameters that are essential for providing network-based mobility
 management service.  This information is typically configured in AAA.
 In some cases, the home network prefix(es) may be dynamically
 assigned to the mobile node's interface, after its initial attachment
 to the Proxy Mobile IPv6 domain over that interface and may not be
 configured in the mobile node's policy profile.
 The network entities in the proxy Mobile IPv6 domain, while serving a
 mobile node, will have access to the mobile node's policy profile and
 these entities can query this information using RADIUS [RFC2865] or
 DIAMETER [RFC3588] protocols.

Appendix B. Routing State

 The following section explains the routing state created 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, et al. Standards Track [Page 89] RFC 5213 Proxy Mobile IPv6 August 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            |
 +------------------------------------------------------------------+
                  Example - Policy-Based Route Table
 +==================================================================+
 | Interface | Source Address | Destination Address | Encapsulation |
 +==================================================================+
 | Tunnel0   |   Proxy-CoA    |        LMAA1         | IPv6-in-IPv6 |
 +------------------------------------------------------------------+
 | Tunnel1   |   Proxy-CoA    |        LMAA2         | IPv6-in-IPv6 |
 +------------------------------------------------------------------+
                   Example - Tunnel Interface Table

Gundavelli, et al. Standards Track [Page 90] RFC 5213 Proxy Mobile IPv6 August 2008

Authors' Addresses

 Sri Gundavelli (editor)
 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
 Vijay Devarapalli
 Wichorus
 3590 North First Street
 San Jose, CA  95134
 USA
 EMail: vijay@wichorus.com
 Kuntal Chowdhury
 Starent Networks
 30 International Place
 Tewksbury, MA
 EMail: kchowdhury@starentnetworks.com
 Basavaraj Patil
 Nokia
 6000 Connection Drive
 Irving, TX  75039
 USA
 EMail: basavaraj.patil@nokia.com

Gundavelli, et al. Standards Track [Page 91] RFC 5213 Proxy Mobile IPv6 August 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.

Gundavelli, et al. Standards Track [Page 92]

/data/webs/external/dokuwiki/data/pages/rfc/rfc5213.txt · Last modified: 2008/08/11 22:14 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki