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Versions: (draft-yokota-mipshop-pfmipv6) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 RFC 5949

Network Working Group                                          H. Yokota
Internet-Draft                                                  KDDI Lab
Intended status: Standards Track                            K. Chowdhury
Expires: June 1, 2010                                          R. Koodli
                                                        Starent Networks
                                                                B. Patil
                                                                   Nokia
                                                                  F. Xia
                                                              Huawei USA
                                                       November 28, 2009


                  Fast Handovers for Proxy Mobile IPv6
                   draft-ietf-mipshop-pfmipv6-11.txt

Abstract

   Mobile IPv6 (MIPv6) [RFC3775] provides a mobile node with IP mobility
   when it performs a handover from one access router to another and
   fast handovers for Mobile IPv6 (FMIPv6) [RFC5568] are specified to
   enhance the handover performance in terms of latency and packet loss.
   While MIPv6 (and FMIPv6 as well) requires the participation of the
   mobile node in the mobility-related signaling, Proxy Mobile IPv6
   (PMIPv6) [RFC5213] provides IP mobility to mobile nodes that either
   have or do not have MIPv6 functionality without such involvement.
   Nevertheless, the basic performance of PMIPv6 in terms of handover
   latency and packet loss is considered not any different from that of
   MIPv6.

   When the fast handover is considered in such an environment, several
   modifications are needed to FMIPv6 to adapt to the network-based
   mobility management.  This document specifies the usage of Fast
   Mobile IPv6 (FMIPv6) when Proxy Mobile IPv6 is used as the mobility
   management protocol.  Necessary extensions are specified for FMIPv6
   to support the scenario when the mobile node does not have IP
   mobility functionality and hence is not involved with either MIPv6 or
   FMIPv6 operations.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

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




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Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   publication of this document.  Please review these documents
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   This document may contain material from IETF Documents or IETF
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   10, 2008.  The person(s) controlling the copyright in some of this
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   Without obtaining an adequate license from the person(s) controlling
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   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.












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Table of Contents

   1.  Requirements notation  . . . . . . . . . . . . . . . . . . . .  4
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  6
   4.  Proxy-based FMIPv6 Protocol Overview . . . . . . . . . . . . .  7
     4.1.  Protocol Operation . . . . . . . . . . . . . . . . . . . .  8
     4.2.  Inter-AR Tunneling Operation . . . . . . . . . . . . . . . 15
     4.3.  IPv4 Support Considerations  . . . . . . . . . . . . . . . 17
   5.  PMIPv6-related Fast Handover Issues  . . . . . . . . . . . . . 18
     5.1.  Manageability Considerations . . . . . . . . . . . . . . . 18
     5.2.  Expedited Packet Transmission  . . . . . . . . . . . . . . 18
   6.  Message Formats  . . . . . . . . . . . . . . . . . . . . . . . 20
     6.1.  Mobility Header  . . . . . . . . . . . . . . . . . . . . . 20
       6.1.1.  Handover Initiate (HI) . . . . . . . . . . . . . . . . 20
       6.1.2.  Handover Acknowledge (HAck)  . . . . . . . . . . . . . 22
     6.2.  Mobility Options . . . . . . . . . . . . . . . . . . . . . 24
       6.2.1.  Context Request Option . . . . . . . . . . . . . . . . 24
       6.2.2.  Local Mobility Anchor Address (LMAA) Option  . . . . . 25
       6.2.3.  Mobile Node Link-local Address Interface
               Identifier (MN LLA-IID) Option . . . . . . . . . . . . 26
       6.2.4.  Home Network Prefix Option . . . . . . . . . . . . . . 27
       6.2.5.  Link-local Address Option  . . . . . . . . . . . . . . 27
       6.2.6.  GRE Key Option . . . . . . . . . . . . . . . . . . . . 27
       6.2.7.  IPv4 Address Option  . . . . . . . . . . . . . . . . . 27
       6.2.8.  Vendor-Specific Mobility Option  . . . . . . . . . . . 27
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 28
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 29
   9.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 30
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 31
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 31
     10.2. Informative References . . . . . . . . . . . . . . . . . . 31
   Appendix A.  Applicable Use Cases  . . . . . . . . . . . . . . . . 32
     A.1.  PMIPv6 Handoff Indication  . . . . . . . . . . . . . . . . 32
     A.2.  Local Routing  . . . . . . . . . . . . . . . . . . . . . . 32
   Appendix B.  Change Log  . . . . . . . . . . . . . . . . . . . . . 34
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 40














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1.  Requirements notation

   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 [RFC2119].














































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2.  Introduction

   Proxy Mobile IPv6 [RFC5213] provides IP mobility to a mobile node
   that does not support Mobile IPv6 [RFC3775] mobile node
   functionality.  A proxy agent in the network performs the mobility
   management signaling on behalf of the mobile node.  This model
   transparently provides mobility for mobile nodes within a PMIPv6
   domain.  Nevertheless, the basic performance of PMIPv6 in terms of
   handover latency and packet loss is considered not any different from
   that of Mobile IPv6.

   Fast Handovers for Mobile IPv6 (FMIPv6) [RFC5568] describes the
   protocol to reduce the handover latency for Mobile IPv6 by allowing a
   mobile node to send packets as soon as it detects a new subnet link
   and by delivering packets to the mobile node as soon as its
   attachment is detected by the new access router.  This document
   describes necessary extensions to FMIPv6 to minimize handover delay
   and packet loss as well as to transfer network-resident context for a
   PMIPv6 handover.
































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3.  Terminology

   This document reuses terminology from [RFC5213], [RFC5568] and
   [RFC3775].  The following terms and abbreviations are additionally
   used in this document.

   Access Network (AN):
        A network composed of link-layer access devices such as access
        points or base stations providing access to an Access Router
        (AR) connected to it.

   Previous Access Network (P-AN):
        The access network to which the Mobile Node (MN) is attached
        before handover.

   New Access Network (N-AN):
        The access network to which the Mobile Node (MN) is attached
        after handover.

   Previous Mobile Access Gateway (PMAG):
        The MAG that manages mobility related signaling for the MN
        before handover.  In this document, the MAG and the Access
        Router are co-located.

   New Mobile Access Gateway (NMAG):
        The MAG that manages mobility related signaling for the MN after
        handover.  In this document, the MAG and the Access Router (AR)
        are co-located.

   Local Mobility Anchor (LMA)
        The topological anchor point for the mobile node's home network
        prefix(es) and the entity that manages the mobile node's binding
        state.  This specification does not alter any capability or
        functionality defined in [RFC5213].

   HO-Initiate:
        A generic signaling message, sent from the P-AN to the PMAG that
        indicates a MN handover.  While this signaling is dependent on
        the access technology, it is assumed that HO-Initiate can carry
        the information to identify the MN and to assist the PMAG
        resolve the NMAG and the new access point or the base station to
        which the MN is moving to.  The details of this message are
        outside the scope of this document.








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4.  Proxy-based FMIPv6 Protocol Overview

   This specification describes fast handover protocols for the network-
   based mobility management protocol called Proxy Mobile IP (PMIPv6)
   [RFC5213].  The core functional entities defined in PMIPv6 are the
   LMA and the MAG.  The LMA is the topological anchor point for the
   MN's home network prefix(es).  The MAG acts as an access router (AR)
   for the MN and performs the mobility management procedures on its
   behalf.  The MAG is responsible for detecting the MN's movements to
   and from the access link and for initiating binding registrations to
   the MN's LMA.  If the MAGs can be informed of the detachment and/or
   attachment of the MN in a timely manner via e.g., the lower layer
   signaling, it will become possible to optimize the handover
   procedure, which involves establishing a connection on the new link
   and signaling between mobility agents, compared to the baseline
   specification of PMIPv6.

   In order to further improve the performance during the handover, the
   PFMIPv6 protocol in this document specifies a bi-directional tunnel
   between the Previous MAG (PMAG) and the New MAG (NMAG) to tunnel
   packets meant for the mobile node.  In order to enable the NMAG to
   send the Proxy Binding Update (PBU), the Handover Initiate (HI) and
   Handover Acknowledge (HAck) messages in [RFC5568] are extended for
   context transfer, in which parameters such as MN's Network Access
   Identifier (NAI), Home Network Prefix (HNP), IPv4 Home Address, are
   transferred from the PMAG.  New flags 'P' and 'F' are defined for the
   HI and HAck messages to distinguish from those in [RFC5568] and to
   request packet forwarding, respectively.

   In this document, the Previous Access Router (PAR) and New Access
   Router (NAR) are interchangeable with the PMAG and NMAG,
   respectively.  The reference network is illustrated in Figure 1.  The
   access networks in the figure (i.e., P-AN and N-AN) are composed of
   Access Points (APs) defined in [RFC5568], which are often referred to
   as base stations in cellular networks.

   Since a MN is not directly involved with IP mobility protocol
   operations, it follows that the MN is not directly involved with fast
   handover procedures either.  Hence, the messages involving the MN in
   [RFC5568] are not used when PMIPv6 is in use.  More specifically, the
   Router Solicitation for Proxy Advertisement (RtSolPr), the Proxy
   Router Advertisement (PrRtAdv), Fast Binding Update (FBU), Fast
   Binding Acknowledgment (FBack) and the Unsolicited Neighbor
   Advertisement (UNA) messages are not applicable in the PMIPv6
   context.






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                                  +----------+
                                  |   LMA    |
                                  |          |
                                  +----------+
                                    /      \
                                   /        \
                                  /          \
                      +........../..+      +..\..........+
                      . +-------+-+ .______. +-+-------+ .
                      . |  PMAG   |()_______)|  NMAG   | .
                      . |  (PAR)  | .      . |  (NAR)  | .
                      . +----+----+ .      . +----+----+ .
                      .      |      .      .      |      .
                      .   ___|___   .      .   ___|___   .
                      .  /       \  .      .  /       \  .
                      . (  P-AN   ) .      . (  N-AN   ) .
                      .  \_______/  .      .  \_______/  .
                      .      |      .      .      |      .
                      .   +----+    .      .   +----+    .
                      .   | MN |  ---------->  | MN |    .
                      .   +----+    .      .   +----+    .
                      +.............+      +.............+

               Figure 1: Reference network for fast handover

4.1.  Protocol Operation

   There are two modes of operation in FMIPv6 [RFC5568].  In the
   predictive mode of fast handover, a bi-directional tunnel between the
   PMAG (PAR) and NMAG (NAR) is established prior to the MN's attachment
   to the NMAG.  In the reactive mode, this tunnel establishment takes
   place after the MN attaches to the NMAG.  In order to alleviate the
   packet loss during a MN's handover (especially when the MN is
   detached from both links), the downlink packets for the MN need to be
   buffered either at the PMAG or NMAG, depending on when the packet
   forwarding is performed.  It is hence required that all MAGs have the
   capability and enough resources to buffer packets for the MNs
   accommodated by them.  The buffer size to be prepared and the rate at
   which buffered packets are drained are addressed in Section 5.4 of
   [RFC5568].  Note that the protocol operation specified in the
   document is transparent to the LMA, hence there is no new functional
   requirement or change on the LMA.

   Unlike MIPv6, the MN in the PMIPv6 domain is not involved with IP
   mobility signaling; therefore, in order for the predictive fast
   handover to work effectively, it is required that the MN is capable
   of reporting lower-layer information to the AN at a short enough
   interval, and the AN is capable of sending the HO-initiate to the



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   PMAG at an appropriate timing.  The sequence of events for the
   predictive fast handover are illustrated in Figure 2.

                                            PMAG        NMAG
          MN         P-AN       N-AN        (PAR)       (NAR)     LMA
          |           |          |            |           |        |
          |  Report   |          |            |           |        |
     (a)  |-(MN ID,-->|          |            |           |        |
          | New AP ID)|          |            |           |        |
          |           |     HO Initiate       |           |        |
     (b)  |           |--(MN ID, New AP ID)-->|           |        |
          |           |          |            |           |        |
          |           |          |            |           |        |
     (c)  |           |          |            |----HI---->|        |
          |           |          |            |           |        |
          |           |          |            |           |        |
     (d)  |           |          |            |<---HAck---|        |
          |           |          |            |           |        |
          |           |          |            |           |        |
          |           |          |            |HI/HAck(optional)   |
     (e)  |           |          |            |<- - - - ->|        |
          |           |          |          #=|<===================|
     (f)  |           |          |          #====DL data=>|        |
          |           |          |            |           |        |
     (g) ~~~          |          |            |           |        |
         ~~~          |          |            |           |        |
          |   MN-AN connection   |    AN-MAG connection   |        |
     (h)  |<---establishment---->|<----establishment----->|        |
          |           |          |  (substitute for UNA)  |        |
          |           |          |            |           |        |
     (i)  |<==================DL data=====================|        |
          |           |          |            |           |        |
     (j)  |===================UL data====================>|=#      |
          |           |          |          #=|<============#      |
          |           |          |          #=====================>|
     /    |           |          |            |           |        | \
     |(k) |           |          |            |           |--PBU-->| |
     |    |           |          |            |           |        | |
     |(l) |           |          |            |           |<--PBA--| |
     |    |<==================DL data=====================|<=======| |
     |    |           |          |            |           |        | |
     \    |===================UL data====================>|=======>| /

       Figure 2: Predictive fast handover for PMIPv6 (PAR initiated)

   The detailed descriptions are as follows:





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   (a)  The MN detects that a handover is imminent and reports the
        identifications of itself (MN ID) and the New Access Point
        Identifier (New AP ID) [RFC5568] to which the MN is most likely
        to move.  The MN ID could be the NAI or a Link Layer Address
        (LLA), or any other suitable identifier.  This step is access
        technology specific.  In some cases, the P-AN will determine
        which AP ID the MN is moving to.

   (b)  The previous access network (P-AN), to which the MN is currently
        attached, indicates the handover of the MN to the PMAG (PMAG).
        Detailed definition and specification of this message are
        outside the scope of this document.

   (c)  The PMAG sends the HI to the NMAG.  The HI message MUST have the
        P flag set and include the MN ID, the HNP(s) and the address of
        the LMA that is currently serving the MN.  If there is a valid
        (non-zero) MN Link-layer Identifier (MN LL-ID), that information
        MUST also be included.  With some link layers, the MN Link-local
        Address IID (MN LLA-IID) can also be included (see
        Section 6.2.3).

   (d)  The NMAG sends the HAck back to the PMAG with the P flag set.

   (e)  If it is preferred that the timing of buffering or forwarding
        should be later than step (c), the NMAG may optionally request
        the PMAG at a later and appropriate time to buffer or forward
        packets by setting U flag [RFC5568] or F flag in the HI message,
        respectively.

   (f)  If the F flag is set in the previous step, a bi-directional
        tunnel is established between the PMAG and NMAG and packets
        destined for the MN are forwarded from the PMAG to the NMAG over
        this tunnel.  After decapsulation, those packets may be buffered
        at the NMAG.  If the connection between the N-AN and NMAG has
        already been established, those packets may be forwarded towards
        the N-AN, which then becomes responsible for them (e.g.,
        buffering or delivering depending on the condition of the MN's
        attachment); this is access technology specific.

   (g)  The MN undergoes handover to the New Access Network (N-AN).

   (h)  The MN establishes a physical link connection with the N-AN
        (e.g., radio channel assignment), which in turn triggers the
        establishment of a link-layer connection between the N-AN and
        NMAG if not yet established.  An IP layer connection setup may
        be performed at this time (e.g., PPP IPv6CP) or at a later time
        (e.g., stateful or stateless auto address configuration).  This
        step can be a substitute for the UNA in [RFC5568].  If the NMAG



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        acquires a valid new MN LL-ID via the N-AN and a valid old MN
        LL-ID from the PMAG at step (c), these IDs SHOULD be compared to
        determine whether the same interface is used before and after
        handover.  When the connection between the MN and NMAG is PPP
        and the same interface is used for the handover, the NMAG SHOULD
        confirm that the same interface identifier is used for the MN's
        link-local address (this is transferred from PMAG using the MN
        LLA-IID option at step (c), and sent to the MN during the
        Configure-Request/Ack exchange).

   (i)  The NMAG starts to forward packets destined for the MN via the
        N-AN.

   (j)  The uplink packets from the MN are sent to the NMAG via the N-AN
        and the NMAG forwards them to the PMAG.  The PMAG then sends the
        packets to the LMA that is currently serving the MN.

   (k)  The NMAG (NAR) sends the Proxy Binding Update (PBU) to the LMA,
        whose address is provided in (c).  Steps (k) and (l) are not
        part of the fast handover procedure, but shown for reference.

   (l)  The LMA sends back the Proxy Binding Acknowledgment (PBA) to the
        NMAG (NMAG).  From this time on, the packets to/from the MN go
        through the NMAG instead of the PMAG.

   According to Section 4 of [RFC5568], the PMAG establishes a binding
   between the Previous Care-of Address (PCoA) and New Care-of Address
   (NCoA) to forward packets for the MN to the NAR, and the NMAG creates
   a proxy neighbor cache entry to receive those packets for the NCoA
   before the MN arrives.  In the case of PMIPv6, however, the only
   address that is used by the MN is MN-HoA (Mobile Node's Home
   Address), so the PMAG forwards MN's packets to the NMAG instead of
   the NCoA.  The NMAG then simply decapsulates those packets and
   delivers them to the MN.  FMIPv4 [RFC4988] specifies forwarding when
   the MN uses the home address as its on-link address rather than the
   care-of address.  The usage in PMIPv6 is similar to that in FMIPv4,
   where the address(es) used by the MN is/are based on its HNP(s).
   Since the NMAG can obtain the Link-layer address (MN LL-ID) and
   HNP(s) via the HI message (also the interface identifier of the MN's
   link-local address (MN LLA-ID) if available), it can create a
   neighbor cache entry for the Link-local Address and the routes for
   the whole HNP(s) even before the MN performs Neighbor Discovery.  For
   the uplink packets from the MN after handover in (j), the NMAG
   forwards the packets to the PMAG through the tunnel established in
   step (f).  The PMAG then decapsulates and sends them to the LMA.

   The timing of the context transfer and that of packet forwarding may
   be different.  Thus, a new flag 'F' and Option Code values for it in



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   the HI and HAck messages are defined to request forwarding.  To
   request buffering, 'U' flag has already been defined in [RFC5568].
   If the PMAG receives the HI message with the F flag set, it starts
   forwarding packets for the MN.  The HI message with the U flag set
   may be sent earlier if the timing of buffering is different from that
   of forwarding.  If packet forwarding is completed, the PMAG MAY send
   the HI message with the F flag set and the Option Code value being 2.
   By this message, the ARs on both ends can tear down the forwarding
   tunnel synchronously.

   The IP addresses in the headers of those user packets are summarized
   below:

   In Step (f),

        Inner source address: IP address of the CN

        Inner destination address: HNP or Mobile Node's IPv4 Home
        Address (IPv4-MN-HoA)

        Outer source address: IP address of the PMAG (PAR)

        Outer destination address: IP address of the NMAG (NAR)

   In Step (i),

        Source address: IP address of the CN

        Destination address: HNP or IPv4-MN-HoA

   In Step (j),

   - from the MN to the NMAG,

        Source address: HNP or IPv4-MN-HoA

        Destination address: IP address of the CN

   - from the NMAG to the PMAG,

        Inner source address: HNP or IPv4-MN-HoA

        Inner destination address: IP address of the CN

        Outer source address: IP address of the NMAG (NAR)






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        Outer destination address: IP address of the PMAG (PAR)

   - from the PMAG to the LMA,

        Inner source address: HNP or IPv4-MN-HoA

        Inner destination address: IP address of the CN

        Outer source address: IP address of the PMAG (PAR)

        Outer destination address: IP address of the LMA






   In the case of the reactive handover for PMIPv6, since the MN does
   not send either the FBU or UNA, it would be more natural that the
   NMAG sends the HI to the PMAG after the MN has moved to the new link.
   The NMAG then needs to obtain the information of the PMAG beforehand.
   Such information could be provided, for example, by the MN sending
   the AP-ID on the old link and/or by the lower-layer procedures
   between the P-AN and N-AN.  The exact method is not specified in this
   document.  Figure 3 illustrates the reactive fast handover procedures
   for PMIPv6, where the bi-directional tunnel establishment is
   initiated by the NMAG.
























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                                         PMAG            NMAG
          MN       P-AN      N-AN        (PAR)           (NAR)     LMA
          |         |         |            |               |        |
     (a) ~~~        |         |            |               |        |
         ~~~        |         |            |               |        |
          |  MN-AN connection |       AN-MAG connection    |        |
     (b)  |<--establishment-->|<-------establishment------>|        |
          |(MN ID, Old AP ID) |     (MN ID, Old AP ID)     |        |
          |         |         |(substitute for UNA and FBU)|        |
          |         |         |            |               |        |
          |         |         |            |               |        |
     (c)  |         |         |            |<-----HI-------|        |
          |         |         |            |               |        |
          |         |         |            |               |        |
     (d)  |         |         |            |-----HAck----->|        |
          |         |         |            |               |        |
          |         |         |            |               |        |
     (e)  |         |         |          #=|<=======================|
          |         |         |          #================>|=#      |
          |<====================DL data======================#      |
          |         |         |            |               |        |
     (f)  |=====================UL data===================>|=#      |
          |         |         |          #=|<================#      |
          |         |         |          #=========================>|
          |         |         |            |               |        |
     /    |         |         |            |               |        | \
     |(g) |         |         |            |               |--PBU-->| |
     |    |         |         |            |               |        | |
     |(h) |         |         |            |               |<--PBA--| |
     |    |<====================DL data====================|<=======| |
     |    |         |         |            |               |        | |
     \    |=====================UL data===================>|=======>| /

        Figure 3: Reactive fast handover for PMIPv6 (NAR initiated)

   The detailed descriptions are as follows:

   (a)  The MN undergoes handover from the P-AN to the N-AN.  The AP-ID
        on the old link may be provided by the MN to help identify the
        PMAG on the new link.

   (b)  The MN establishes a connection (e.g., radio channel) with the
        N-AN, which triggers the establishment of the connection between
        the N-AN and NMAG.  The MN ID is transferred to the NMAG for the
        subsequent procedures.  The AP-ID on the old link may also be
        provided by the MN to help identify the PMAG on the new link.
        This can be regarded as a substitute for the UNA and FBU.




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   (c)  The NMAG sends the HI to the PMAG.  The HI message MUST have the
        P flag set and include the MN ID.  The Context Request Option
        MAY be included to request additional context information on the
        MN to the PMAG.

   (d)  The PMAG sends the HAck back to the NMAG with the P flag set.
        The HAck message MUST include the HNP(s) and/or IPv4-MN-HoA that
        is corresponding to the MN ID in the HI message and SHOULD
        include the MN LL-ID, only if it is valid (non zero), and the
        LMA address that is currently serving the MN.  The context
        information requested by the NMAG MUST be included.  If the
        requested context is not available for some reason, the PMAG
        MUST return the HAck with the Code value 131.  If the F flag is
        set in the HI at step (c) and forwarding is nevertheless not
        executable for some reason, the PMAG MUST return the HAck with
        the Code value 132.

   (e)  If the F flag in the HI is set at step (c), a bi-directional
        tunnel is established between the PMAG and NMAG and packets
        destined for the MN are forwarded from the PMAG to the NMAG over
        this tunnel.  After decapsulation, those packets are delivered
        to the MN via the N-AN.

   (f)  The uplink packets from the MN are sent to the NMAG via the N-AN
        and the NMAG forwards them to the PMAG.  The PMAG then sends the
        packets to the LMA that is currently serving the MN.

   Steps (g)-(h) are the same as (k)-(l) in the predictive fast handover
   procedures.

   In step (c), The IP address of the PMAG needs to be resolved by the
   NMAG to send the HI to the PMAG.  This information may come from the
   N-AN or some database that the NMAG can access.

4.2.  Inter-AR Tunneling Operation

   When the PMAG (PAR) or NMAG (NAR), depending on the fast handover
   mode, receives the HI message with the F flag set, it prepares to
   send/receive the MN's packets to/from the other MAG and returns the
   HAck message with the same sequence number.  The both MAGs SHOULD
   support the following encapsulation modes for the user packets, which
   are also defined for the tunnel between the LMA and MAG:

   o  IPv4-or-IPv6-over-IPv6 [IPv4PMIPv6]

   o  IPv4-or-IPv6-over-IPv4 [IPv4PMIPv6]





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   o  IPv4-or-IPv6-over-IPv4-UDP [IPv4PMIPv6]

   o  TLV-header UDP tunneling [GREKEY]

   o  GRE tunneling with or without GRE key(s) [GREKEY]

   The PMAG and the NMAG MUST use the same tunneling mechanism for the
   data traffic tunneled between them.  The encapsulation mode to be
   employed SHOULD be configurable.  This specification recommends the
   following:

   1.  As the default behavior, the inter-MAG tunnel uses the same
       encapsulation mechanism as that for the PMIPv6 tunnel between the
       LMA and the MAGs.  The PMAG and NMAG automatically start using
       the same encapsulation mechanism without a need for a special
       configuration on the MAGs or a dynamic tunneling mechanism
       negotiation between them.

   2.  Configuration on the MAGs can override the default mechanism
       specified in #1 above.  The PMAG and NMAG MUST be configured with
       the same mechanism and this configuration is most likely to be
       uniform throughout the PMIPv6 domain.  If the packets on the
       PMIPv6 tunnel cannot be uniquely mapped on to the configured
       inter-MAG tunnel, this scenario is not applicable and scenario #3
       below SHOULD directly be applied.

   3.  An implicit or explicit tunnel negotiation mechanism between the
       MAGs can override the default mechanism specified in #1 above.
       The employed tunnel negotiation mechanism is outside the scope of
       this document.

   The necessary information MUST be transferred in the HI/HAck messages
   to distinguish MN's packets for forwarding in advance or at this
   time.  Such information includes the HNP(s) (or IPv4-MN-HoA) and/or
   GRE key(s).  In the case of GRE tunneling with GRE keys being used,
   for each mobility session, the NMAG selects the GRE key for the
   downlink packets and the PMAG selects the GRE key for the uplink
   packets.  These GRE keys are exchanged between the PMAG and the NMAG
   using the GRE Key option as described in [GREKEY], e.g., In the case
   of the reactive mode as shown in Figure 3, the DL GRE key is
   communicated in the HI message while the UL GRE key is sent in the
   HAck message.  For the downlink packets, the PMAG redirects MN's
   packets from the LMA towards the NMAG and if the MN is ready to
   receive those packets or the N-AN can handle them regardless of the
   state of the MN, the NMAG should immediately send them towards the
   N-AN; otherwise it should buffer them until the MN is ready.  For the
   uplink packets, the NMAG SHOULD reverse-tunnel them from the MN
   towards the PMAG and the PMAG sends them to the LMA.



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   When the PMAG or NMAG receives the HI message with the U flag set, it
   prepares to buffer the MN's packets and returns the HAck message with
   the same sequence number.  It MUST be followed by another HI message
   with the F flag set at an appropriate time to forward the buffered
   packets.

   If the MAG that received the HI message encounters an erroneous
   situation (e.g., insufficient buffer space), it SHOULD immediately
   send the HAck message with the cause of the error and cancel all
   tunneling operation.

4.3.  IPv4 Support Considerations

   The motivation and usage scenarios of IPv4 protocol support by PMIPv6
   are described in [IPv4PMIPv6].  The scope of IPv4 support covers the
   following two features:

   o  IPv4 Home Address Mobility Support, and

   o  IPv4 Transport Support.

   As for IPv4 Home Address Mobility Support, the MN acquires IPv4 Home
   Address (IPv4-MN-HoA) and in the case of handover, the PMAG needs to
   transfer IPv4-MN-HoA to the NMAG, which is the inner destination
   address of the packets forwarded on the downlink.  For this purpose,
   IPv4 Address Option described in Section 6.2.7 is used.  In order to
   provide IPv4 Transport Support, the NMAG needs to know the IPv4
   address of the LMA (IPv4-LMAA) to send PMIPv6 signaling messages to
   the LMA in the IPv4 transport network.  For this purpose, a new
   option called LMA Address (LMAA) Option is defined in Section 6.2.2
   so as to convey IPv4-LMAA from the PMAG to NMAG.




















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5.  PMIPv6-related Fast Handover Issues

5.1.  Manageability Considerations

   This specification does not require any additional IP-level
   functionality on the LMA and the MN running in the PMIPv6 domain.  A
   typical network interface that the MN could be assumed to have is one
   with the cellular network, where the network controls the movement of
   the MN.  Different types of interfaces could be involved such as
   different generations (3G and 3.9G) or different radio access
   systems.  This specification supports a MN with the single radio
   mode, where only one interface is active at any given time.  The
   assigned IP address is preserved whether the physical interface
   changes or not and the MN can identify which interface should be used
   if there are multiple ones.

5.2.  Expedited Packet Transmission

   The protocol specified in this document enables the NMAG to obtain
   parameters which would otherwise be available only by communicating
   with the LMA.  For instance, the HNP(s) and/or IPv4-MN-HoA of a MN
   are made available to the NMAG through context transfer.  This allows
   the NMAG to perform some procedures that may be beneficial.  The
   NMAG, for example, could send a Router Advertisement (RA) with the
   HNP option to the MN as soon as its link attachment is detected
   (e.g., via receipt of a Router Solicitation message).  Such an RA is
   recommended, for example, in scenarios where the MN uses a new radio
   interface while attaching to the NMAG; since the MN does not have
   information regarding the new interface, it will not be able to
   immediately send packets without first receiving an RA with HNP(s).
   Especially, in the reactive fast handover, the NMAG gets to know the
   HNP(s) assigned to the MN on the previous link at step (d) in
   Figure 3.  In order to reduce the communication disruption time, the
   NMAG SHOULD expect the MN to keep using the same HNP and to send
   uplink packets before that step upon the MN's request.  However, if
   the HAck from the PMAG returns a different HNP or the subsequent
   PMIPv6 binding registration for the HNP fails for some reason, then
   the NMAG MUST withdraw the advertised HNP by sending another RA with
   zero prefix lifetime for the HNP in question.  This operation is the
   same as described in Section 6.12 of [RFC5213].

   The protocol specified in this document is applicable regardless of
   whether link-layer addresses are used between a MN and its access
   router.  A MN should be able to continue sending packets on the
   uplink even when it changes link.  When link-layer addresses are
   used, the MN performs Neighbor Unreachability Detection (NUD)
   [RFC4861], after attaching to a new link, probing the reachability of
   its default router.  The new router should respond to the NUD probe,



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   providing its link-layer address in the solicited Neighbor
   Advertisement, which is common in the PMIPv6 domain.  Implementations
   should allow the MN to continue to send uplink packets while it is
   performing NUD.















































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6.  Message Formats

   This document defines new Mobility Header messages for the extended
   HI and Hack and new mobility options for conveying context
   information.

6.1.  Mobility Header

6.1.1.  Handover Initiate (HI)

   This section defines extensions to the HI message in [RFC5568].  The
   format of the Message Data field in the Mobility Header 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
                                     +-------------------------------+
                                     |           Sequence #          |
     +-+-+-+-+-------+---------------+-------------------------------+
     |S|U|P|F|Resv'd |      Code     |                               |
     +-+-+-+-+-------+---------------+                               |
     |                                                               |
     .                                                               .
     .                       Mobility options                        .
     .                                                               .
     |                                                               |
     +---------------------------------------------------------------+
     (Note:P=1)

   IP Fields:

   Source Address

                       The IP address of PMAG or NMAG

   Destination Address

                       The IP address of the peer MAG

   Message Data:

   Sequence #  Same as [RFC5568].

   S flag      Defined in [RFC5568] and MUST be set to zero in this
               specification.






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   U flag      Buffer flag.  Same as [RFC5568].

   P flag      Proxy flag.  Used to distinguish the message from that
               defined in [RFC5568] and MUST be set in all new message
               formats defined in this document when using this protocol
               extension.

   F flag      Forwarding flag.  Used to request to forward the packets
               for the MN.

   Reserved    Same as [RFC5568].

   Code        [RFC5568] defines this field and its values 0 and 1.  In
               this specification, with the P flag set, this field can
               be set to zero by default or the following values:

                         2: Indicate the completion of forwarding

                         3: All available context transferred

               Code value 3 is set when the transfer of all necessary
               context information is completed with this message.  This
               Code value is used in both cases where the context
               information is fragmented into several pieces and the
               last fragment is contained in this message and where the
               whole information is transferred in one piece.

   Mobility options:

   This field contains one or more mobility options, whose encoding and
   formats are defined in [RFC3775].

   Requested option
             In order to uniquely identify the target MN, the MN
             Identifier MUST be contained in the Mobile Node Identifier
             Option.

   The transferred context MUST be for one MN per message.  In addition,
   the NMAG can request necessary mobility options by the Context
   Request Option defined in this document.

   Context Request Option

            This option MAY be present to request context information
            typically by the NMAG to the PMAG in the NAR-initiated fast
            handover.





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6.1.2.  Handover Acknowledge (HAck)

   This section defines extensions to the HAck message in[RFC5568].  The
   format of the Message Data field in the Mobility Header 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
                                     +-------------------------------+
                                     |           Sequence #          |
     +-+-+-+---------+---------------+-------------------------------+
     |U|P|F|Reserved |      Code     |                               |
     +-+-+-+---------+---------------+                               |
     |                                                               |
     .                                                               .
     .                       Mobility options                        .
     .                                                               .
     |                                                               |
     +---------------------------------------------------------------+
     (Note:P=1)

   IP Fields:

   Source Address

                       Copied from the destination address of the
                       Handover Initiate message to which this message
                       is a response.

   Destination Address

                       Copied from the source address of the Handover
                       Initiate message to which this message is a
                       response.

   Message Data:

   The usages of Sequence # and Reserved fields are exactly the same as
   those in [RFC5568].

   U flag      Same as defined in Section 6.1.1.

   P flag      Used to distinguish the message from that defined in
               [RFC5568] and MUST be set in all new message formats
               defined in this document when using this protocol
               extension.





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   F flag      Same as defined in Section 6.1.1.

   Code
               Code values 0 through 4 and 128 through 130 are defined
               in [RFC5568].  In this specification, the meaning of Code
               value 0 is modified, 128 through 130 are reused, and 5,
               6, 131 and 132 are newly defined.

                       0: Handover Accepted or Successful

                       5: Context Transfer Accepted or Successful

                       6: All available Context Transferred

                       128: Handover Not Accepted, reason unspecified

                       129: Administratively prohibited

                       130: Insufficient resources

                       131: Requested Context Not Available

                       132: Forwarding Not Available

   Mobility options:

   This field contains one or more mobility options, whose encoding and
   formats are defined in [RFC3775].  The mobility option that uniquely
   identifies the target MN MUST be copied from the corresponding HI
   message and the transferred context MUST be for one MN per message.

   Requested option(s)  All the context information requested by the
             Context Request Option in the HI message SHOULD be present
             in the HAck message.  The other cases are described below.

   In the case of the PAR-initiated fast handover, when the PMAG sends
   the HI message to the NMAG with the context information and the NMAG
   successfully receives it, the NMAG returns the HAck message with Code
   value 5.  In the case of the NAR-initiated fast handover, when the
   NMAG sends the HI message to the PMAG with or without Context Request
   Option, the PMAG returns the HAck message with the requested or
   default context information (if any).  If all available context
   information is transferred, the PMAG sets the Code value in the HAck
   message to 6.  If more context information is available, the PMAG
   sets the Code value in the HAck to 5 and the NMAG MAY send new HI
   message(s) to retrieve the rest of the available context information.
   If none of the requested context information is available, the PMAG
   returns the HAck message with Code value 131 without any context



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   information.

6.2.  Mobility Options

6.2.1.  Context Request Option

   This option is sent in the HI message to request context information
   on the MN.  If a default set of context information is defined and
   always sufficient, this option is not used.  This option is more
   useful to retrieve additional or dynamically selected context
   information.

   Context Request Option is typically used for the reactive (NAR-
   initiated) fast handover mode to retrieve the context information
   from the PMAG.  When this option is included in the HI message, all
   the requested context information SHOULD be included in the HAck
   message in the corresponding mobility option(s) (e.g., HNP, LMAA or
   MN LL-ID mobility options).

   The default context information to request is the Home Network Prefix
   Option.  If the Mobile Node link-layer is available and used, the
   Mobile Node Link-layer Identifier Option MUST also be requested.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +---------------+---------------+---------------+---------------+
     |  Option-Type  | Option-Length |           Reserved            |
     +---------------+---------------+-------------------------------+
     |  Req-type-1   | Req-length-1  |  Req-type-2   | Req-length-2  |
     +---------------------------------------------------------------+
     |  Req-type-3   | Req-length-3  |          Req-option-3         |
     +---------------------------------------------------------------+
     |                              ...                              |

   Option-Type    TBD1

   Option-Length  The length in octets of this option, not including the
                  Option Type and Option Length fields.

   Reserved       This field is unused.  It MUST be initialized to zero
                  by the sender and MUST be ignored by the receiver.

   Req-type-n     The type value for the n'th requested option.

   Req-length-n   The length of the n'th requested option excluding the
                  Req-type-n and Req-length-n fields.





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   Req-option-n   The optional data to uniquely identify the requested
                  context for the n'th requested option.

   In the case where there are only Req-type-n and Req-length-n fields,
   the value of the Req-length-n is set to zero.  If additional
   information besides the Req-type-n is necessary to uniquely specify
   the requested context, such information follows after the
   Req-length-n.  For example, when the requested contexts start with
   the HNP Option (type=22), the MN Link-layer ID Option (type=25) and
   the Vendor-Specific Option (type=19), the requested option format
   looks as follows:

     |                              ...                              |
     +---------------+---------------+---------------+---------------+
     |Option-Type=CRO| Option-Length |           Reserved            |
     +---------------+---------------+---------------+---------------+
     | Req-type-N=22 | Req-length-N=0| Req-type-N=25 | Req-length-N=0|
     +---------------+---------------+-------------------------------+
     | Req-type-N=19 | Req-length-N=5|           Vendor-ID           |
     +-------------------------------+---------------+---------------+
     |           Vendor-ID           |   Sub-Type    |               |
     +-----------------------------------------------+               |
     |                              ...                              |

   The first two options can uniquely identify the requested contexts
   (i.e., the HNP and MN Link-layer ID) by the Req-type, so the Req-
   length is set to zero; however, the subsequent Vendor-Specific Option
   further needs the Vendor-ID and Sub-type to identify the requested
   context, so these parameters follow and the Req-length is set to 5.
   Note that the exact values in the Vendor-ID ans Sub-Type follow
   [RFC5094].

6.2.2.  Local Mobility Anchor Address (LMAA) Option

   This option is used to transfer the Local Mobility Anchor IPv6
   Address (LMAA) or its IPv4 Address (IPv4-LMAA), with which the MN is
   currently registered.  The detailed definition of the LMAA is
   described in [RFC5213].

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Option-Type  | Option-Length |  Option-Code  |   Reserved    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |              Local Mobility Anchor Address ...                |






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   Option-Type    TBD2

   Option-Length  18 or 6

   Option-Code

                  0  Reserved

                  1  IPv6 address of the LMA (LMAA)

                  2  IPv4 address of the LMA (IPv4-LMAA)

   Reserved       This field is unused.  It MUST be initialized to zero
                  by the sender and MUST be ignored by the receiver.

   Local Mobility Anchor Address
                  If Option-Code is 1, the LMA IPv6 address (LMAA) is
                  inserted.  If Option-Code is 2, the LMA IPv4 address
                  (IPv4-LMA) is inserted.

6.2.3.  Mobile Node Link-local Address Interface Identifier (MN LLA-IID)
        Option

   This option is used to transfer the interface identifier of the MN's
   IPv6 Link-local Address that is used in the P-AN.  In deployments
   where the interface identifier is assigned by the network, or it is
   known to the network, this option is used to transfer this identifier
   from the PMAG to NMAG.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Option-Type   | Option-Length |            Reserved           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +                      Interface Identifier                     +
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Option-Type    TBD3

   Option-Length  10

   Reserved       This field is unused.  It MUST be initialized to zero
                  by the sender and MUST be ignored by the receiver.






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   Interface Identifier
                  The Interface Identifier value used for the MN's IPv6
                  Link-local address in the P-AN.

6.2.4.  Home Network Prefix Option

   This option is used to transfer the home network prefix that is
   assigned to the MN in the P-AN.  The Home Network Prefix Option
   defined in [RFC5213] is used for this.

6.2.5.  Link-local Address Option

   This option is used to transfer the link-local address of the PMAG
   (PMAG).  The Link-local Address Option defined in [RFC5213] is used
   for this.

6.2.6.  GRE Key Option

   This option is used to transfer the GRE Key for the MN's data flow
   over the bi-directional tunnel between the PMAG and NMAG.  The
   message format of this option follows the GRE Key Option defined in
   [GREKEY].  The GRE Key value uniquely identifies each flow and the
   sender of this option expects to receive packets of the flow from the
   peer AR with this value.

6.2.7.  IPv4 Address Option

   As described in Section 4.3, if the MN runs in IPv4-only mode or
   dual-stack mode, it requires IPv4 home address (IPv4-MN-HoA).  This
   option is used to transfer the IPv4 home address if assigned on the
   previous link.  The format of this option follows the IPv4 Home
   Address Request Option defined in [IPv4PMIPv6].

6.2.8.  Vendor-Specific Mobility Option

   This option is used to transfer any other information defined in this
   document.  The format and used values of this option follow the
   Vendor-Specific Mobility Option defined in [RFC5094].













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7.  Security Considerations

   Security issues for this document follow those for PMIPv6 [RFC5213]
   and FMIPv6 [RFC5568].  In PMIPv6, the MAG and LMA are assumed to
   share security associations.  In FMIPv6, the access routers (i.e.,
   the PMAG and NMAG in this document) are assumed to share security
   associations.

   The Handover Initiate (HI) and Handover Acknowledge (HAck) messages
   exchanged between the PMAG and NMAG MUST be protected using end-to-
   end security association(s) offering integrity and data origin
   authentication.  The PMAG and the NMAG MUST implement IPsec [RFC4301]
   for protecting the HI and HAck messages.  IPsec Encapsulating
   Security Payload (ESP) [RFC4303] in transport mode with mandatory
   integrity protection SHOULD be used for protecting the signaling
   messages.  Confidentiality protection SHOULD be used if sensitive
   context related to the mobile node is transferred.

   IPsec ESP [RFC4303] in tunnel mode SHOULD be used to protect the MN's
   packets at the time of forwarding if the link between the PMAG and
   NMAG exposes the MN's packets to more threats than if they had
   followed their normal routed path.





























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8.  IANA Considerations

   This document defines new flags and status codes in the HI and HAck
   messages as well as three new mobility options.  The Type values for
   these mobility options are assigned from the same numbering space as
   allocated for the other mobility options defined in [RFC3775].

    Mobility Options
    Value  Description                              Reference
    -----  -------------------------------------    -------------
    TBD1   Context Request Option                   Section 6.2.1
    TBD2   Local Mobility Anchor Address Option     Section 6.2.2
    TBD3   Mobile Node Link-local Address
                    Interface Identifier Option     Section 6.2.3

    Handover Initiate Flags
    Flag  Value  Description                        Reference
    ----  -----  -------------------------------    -------------
      P   0x20   Proxy flag                         Section 6.1.1
      F   0x10   Forwarding flag                    Section 6.1.1

    Handover Acknowledge Flags
    Flag  Value  Description                        Reference
    ----  -----  -------------------------------    -------------
      P   0x40   Proxy flag                         Section 6.1.2
      F   0x20   Forwarding flag                    Section 6.1.2

    Handover Initiate Status Codes
    Code  Description                               Reference
    ----  --------------------------------------    -------------
      2   Indicate the completion of forwarding     Section 6.1.1
      3   All available context transferred         Section 6.1.1

    Handover Acknowledge Status Codes
    Code  Description                               Reference
    ----  --------------------------------------    -------------
      0   Handover Accepted or Successful           Section 6.1.2
      5   Context Transfer Accepted or Successful   Section 6.1.2
      6   All available Context Transferred         Section 6.1.2
    131   Requested Context Not Available           Section 6.1.2
    132   Forwarding Not Available                  Section 6.1.2










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9.  Acknowledgments

   The authors would like to specially thank Vijay Devarapalli and Sri
   Gundavelli for their thorough reviews of this document.

   The authors would also like to thank Charlie Perkins, Desire Oulai,
   Ahmad Muhanna, Giaretta Gerardo, Domagoj Premec, Marco Liebsch, Fan
   Zhao, Julien Laganier and Pierrick Seite for their passionate
   discussions in the working group mailing list.










































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10.  References

10.1.  Normative References

   [RFC5213]  Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
              and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.

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

   [RFC5568]  Koodli, R., "Mobile IPv6 Fast Handovers", RFC 5568,
              July 2009.

   [RFC3775]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
              in IPv6", RFC 3775, June 2004.

   [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.

   [RFC5094]  Devarapalli, V., Patel, A., and K. Leung, "Mobile IPv6
              Vendor Specific Option", RFC 5094, December 2007.

   [IPv4PMIPv6]
              Wakikawa, R., Ed. and S. Gundavelli, "IPv4 Support for
              Proxy Mobile IPv6",
               draft-ietf-netlmm-pmip6-ipv4-support-17.txt,
              September 2009.

   [GREKEY]   Muhanna, A., Ed., "GRE Key Option for Proxy Mobile IPv6",
               draft-ietf-netlmm-grekey-option-09.txt, May 2009.

10.2.  Informative References

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              September 2007.

   [RFC4988]  Koodli, R. and C. Perkins, "Mobile IPv4 Fast Handovers",
              RFC 4988, October 2007.









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Appendix A.  Applicable Use Cases

A.1.  PMIPv6 Handoff Indication

   PMIPv6 [RFC5213] defines the Handoff Indicator Option and describes
   the type of the handoff and the values to set to the option.  This
   document proposes one approach to determining the handoff type by the
   NMAG when the handoff of the MN is executed.

   According to [RFC5213], the following handoff types are 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)

   Assuming that there is a valid MN Link-layer Identifier (MN LL-ID),
   the following solution can be considered.  When the NMAG receives the
   MN LL-ID from the PMAG in the MN LL-ID option via the HI or HAck
   message, the NMAG compares it with the new MN LL-ID that is obtained
   from the MN in the N-AN.  If these two MN LL-IDs are the same, the
   handoff type falls into 3) and the Handoff Indicator value is set to
   3.  If these two MN LL-IDs are different, the handoff is likely to be
   2) since the HI/HAck message exchange implies that this is a handoff
   not a multi-homing, therefore the Handoff Indicator value can be set
   to 2.  If there is no HI/HAck exchange performed prior to the network
   attachment of the MN in the N-AN, the NMAG may infer that this is a
   multi-homing case and set the Handoff Indicator value to 1.  In the
   case of re-registration, the MAG, to which the MN is attached, can
   determine if the handoff state is not changed, so the MAG can set the
   HI value to 5 without any additional information.  If none of them
   can be assumed or there is no valid MN LL-ID available, the NMAG may
   set the value to 4.

A.2.  Local Routing

   Section 6.10.3 in [RFC5213] describes that if EnableMAGLocalRouting
   flag is set, when two mobile nodes are attached to one MAG, the
   traffic between them may be locally routed.  If one mobile node moves
   from this MAG (PMAG) to another MAG (NMAG) and if the PMAG does not
   detect the MN's detachment, it will continue to forward packets



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   locally forever.  This situation is more likely to happen in the
   reactive fast handover with WLAN access, which does not have the
   capability to detect the detachment of the MN in a timely manner.
   PFMIPv6 can be applied to handle this case.  When the MN attaches to
   the NMAG, the NMAG sends the HI message to the PMAG with the 'F' flag
   set, which makes the PMAG realize the detachment of the MN and
   establish the inter-MAG tunnel.  The PMAG immediately stops the local
   routing and sends the packets for the MN to the NMAG via that tunnel,
   which are then delivered to the MN on the new link.










































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Appendix B.  Change Log

   Changes at -00

      *  Added separate sections for MH and ICMP.

      *  Clarified usage of HNP and IPv4-MN-HoA throughout the document.

      *  Added IANA Considerations.

      *  Added section on Other Considerations, including operation of
         uplink packets when using link-layer addresses, multiple
         interface usage and transmission of RA to withdraw HNP in the
         event of failure of PMIP6 registration.

      *  Revised Security Considerations.

   Changes from -00 to -01

      *  Removed ICMPv6-based message format.

      *  Clarified HI/HAck exchange in the predictive mode (step (e) in
         Figure 2).

      *  Clarified information retrieval about the PMAG in the reactive
         mode.

      *  Removed the extension to the GRE Key Option.

      *  Clarified the handoff type considerations in Appendix A.

      *  Home Network Prefix Option, Link-local Address Option and
         Vendor-Specific Mobility Option are added.

   Changes from -01 to -02

      *  Aligned HI/HAck message formats with
         draft-ietf-mipshop-rfc5268bis-00.txt.

      *  Revised Section 8 removing the request for the type assignment
         of HI/HAck Mobility Headers.

   Changes from -02 to -03

      *  Updated HI/HAck message formats according to
         draft-ietf-mipshop-rfc5268bis-01.txt.





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      *  Cleaned up Figure 2 and Figure 3.

      *  Moved PMIP domain boundary crossing situation in Section 4.1 to
         Appendix A.3.

      *  Removed the alternative protocol operation with an unsolicited
         HAck from Section 4.1.

      *  Modified Code values in the HAck message in order to avoid
         collision with those in draft-ietf-mipshop-rfc5268bis-01.txt.

      *  Clarified the usage scenarios of Context Request Option.

      *  Modified the description of Code values in the HAck message.

      *  Changed the container for the IPv4-LMAA from IPv4 Address
         option to the LMAA option.

      *  Made Confidentiality protection "SHOULD" for context transfer.

   Changes from -03 to -04

      *  Added more explanations about MIPv6, FMIPv6 and PMIPv6 in
         Abstract.

      *  Moved Figure 1 to Section 4.

      *  More clearly indicated the FMIPv6 messages that are not
         applicable in the PMIPv6 context.

      *  Mandated the support of IP Sec on the PMAG and NMAG in order to
         protect signaling and user packets and the context information.

      *  Added a new section for the inter-AR tunneling operation
         (Section 4.2).

      *  Added descriptions about the encapsulation type in Sections 4.1
         and 4.3.

      *  Added a description about buffering requirements on the MAG in
         Section 4.1.

      *  Added a description about the timing of L2 and L3 connection
         establishments in Section 4.1.

      *  Added a new section for PMIPv6-related fast handover issues
         (Section 5) and a description about preferable behaviors of the
         MN and MAG to reduce packet loss.



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      *  Added Acknowledgments section (Section 9).

      *  Added a new section for local routing in Appendix (A.2).

   Changes from -04 to -05

      *  Fixed Figure 2 (step (i)).

      *  Defined the Mobile Network Interface Identifier (MN-IID)
         mobility option in Section 6.2.4 (swapped with old Section
         6.2.5), and added it to IANA considerations (Section 8).

      *  Changed from SHOULD to MUST regarding the inclusion of the
         MN-ID, MN-HNP, MN-IID and the LMAA options in the HI message
         (step (c) in Section 4.1).

      *  The optional behavior of the NMAG that allows it to send uplink
         packets directly to the LMA before the PBU/PBA exchange was
         removed from section 4.2 (as out of scope).

      *  In Section A.3, the description about the HA address assignment
         from the NAR to the MN was removed (as out of scope).

   Changes from -05 to -06

      *  Added 'P' flag in the HI and Hack messages to distinguish them
         from those in FMIPv6.

      *  Made editorial corrections in Section 2 (Introduction), Section
         3 (Terminology), Section 4 (Protocol Overview) and Section 4.2
         (Inter-AR Tunneling Operation).

      *  Added a description on how forwarded packets should be handled
         in the access network at step (f) in Section 4.1.

      *  Added all types of encapsulation methods that should be
         supported in Section 4.1.

      *  Revised the Code values for the HI message in Section 6.1.1.

      *  Revised the Code values for the HAck message in Section 6.1.2
         and added a description of its usage at step (d) of the
         reactive handover mode in Section 4.1.

      *  Removed the definition of the IP Address Option in Section
         6.2.3 and moved to Section 6.2.7, which currently refers to the
         IPv4 Home Address Option defined by RFC5555.  Revised the IANA
         Consideration section accordingly.



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      *  Removed the Option-Code from the Mobile Node Identifier (MN
         IID) Option.

      *  Removed Appendix A.3 (Handling of PMIPv6/MIPv6 switching).

   Changes from -06 to -07

      *  Added explanations about defining and setting the 'P' flag for
         the HI and Hack messages in Sections 4 and 4.1.

      *  Corrected the references for the encapsulation types in Section
         4.1.

      *  Modified the Code values for the HI message in Section 6.1.1 to
         avoid overlapping with those in
         draft-ietf-mipshop-rfc5268bis-01.txt.

      *  Modified the reference for the IPv4 Address Option from RFC5555
         to [IPv4PMIPv6] in Section 6.2.7.

   Changes from -07 to -08

      *  Corrected the reference for the TLV-header UDP encapsulation in
         Section 4.1.

      *  Updated the version number of the reference document
         [IPv4PMIPv6] and the option name defined by that document in
         Section 6.2.7.

   Changes from -08 to -09

      *  Added a paragraph at the beginning of Section 4 describing the
         assumption related to the lower layer signaling.

      *  Added a new section on the manageability considerations in
         Section 5 describing the configurations on the network and the
         mobile node assumed in this document.

      *  Modified the assumed configuration of the MAG regarding its
         link-layer address in Section 5 (Section 5.2 in version -09).

      *  Specified the requested option to identify the target MN for
         the inter-AR tunneling in Section 6.1.1.

      *  Specified the default context information in the Context
         Request Option in Section 6.2.1.





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   Changes from -09 to -10

      *  Revised the document based on the comments from TSV-DIR, SEC-
         DIR, OPS-DIR and GEN-ART.

         +  Split the abstract section in half for readability.

         +  Added the definition of Localized Mobility Anchor (LMA) in
            Section 3.

         +  Added the purpose of this document at the beginning of
            Section 4 to make the paragraph more complete.

         +  Revised the third paragraph of the Security Consideration
            section for more precise expression.

         +  Moved the description about the requirement to set the 'P'
            flag in HI/HAck to Sections 6.1.1 and 6.1.2.  Also, noted
            the 'P' flag setting below the message formats.

         +  Described the both 'P' and 'F' flags as newly defined ones
            in Section 4.

         +  Clarified the usage of the Context Request Option if a
            default set of context information is defined in Section
            6.2.1 (changed from "not mandatory" to "not used").

         +  Modified the identifier for the interface on the MN to the
            MN's link-layer ID (MN LL-ID).

         +  Corrected the local routing operation of the PMAG in
            Appendix A.2.

      *  Revised the descriptions about the encapsulation mechanism for
         the inter-MAG tunnel in Section 4.2 and other related parts for
         clarification.

      *  Also listed the new flags and status codes for the HI/HAck
         messages in the IANA Considerations section.

      *  Elaborated on the example use of the Context Request Option in
         Section 6.2.1.

   Changes from -10 to -11

      *  Changed the term "MN Interface Identifier (MN-IID) option" to
         "MN Link-local Address Interface Identifier (MN LLA-IID)
         option" in Section 6.2.3.  Its usage is valid only when the



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         network assigns the interface identifier.

      *  Revised the description of the neighbor cache entry in Section
         4.1 to include the MN LLA-IID.















































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Authors' Addresses

   Hidetoshi Yokota
   KDDI Lab
   2-1-15 Ohara, Fujimino
   Saitama,  356-8502
   Japan

   Email: yokota@kddilabs.jp


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

   Email: kchowdhury@starentnetworks.com


   Rajeev Koodli
   Starent Networks
   30 International Place
   Tewksbury, MA  01876
   USA

   Email: rkoodli@starentnetworks.com


   Basavaraj Patil
   Nokia
   6000 Connection Drive
   Irving, TX  75039
   USA

   Email: basavaraj.patil@nokia.com


   Frank Xia
   Huawei USA
   1700 Alma Dr. Suite 500
   Plano, TX  75075
   USA

   Email: xiayangsong@huawei.com






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