Network Working Group                                   J. Korhonen, Ed.
Internet-Draft                                    Nokia Siemens Networks
Intended status: Standards Track                           S. Gundavelli
Expires: April 2, 2011                                             Cisco
                                                               H. Yokota
                                                                KDDI Lab
                                                                  X. Cui
                                                     Huawei Technologies
                                                      September 29, 2010


          Runtime LMA Assignment Support for Proxy Mobile IPv6
                   draft-ietf-netext-redirect-04.txt

Abstract

   This document describes a runtime Local Mobility Anchor assignment
   functionality and corresponding mobility options for Proxy Mobile
   IPv6.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 2, 2011.

Copyright Notice

   Copyright (c) 2010 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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Requirements and Terminology . . . . . . . . . . . . . . . . .  5
     2.1.  Requirements . . . . . . . . . . . . . . . . . . . . . . .  5
     2.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Proxy Mobile IPv6 Domain Assumptions . . . . . . . . . . . . .  6
   4.  Mobility Options . . . . . . . . . . . . . . . . . . . . . . .  7
     4.1.  Redirect-Capability Mobility Option  . . . . . . . . . . .  7
     4.2.  Redirect Mobility Option . . . . . . . . . . . . . . . . .  7
   5.  Runtime LMA Assignment . . . . . . . . . . . . . . . . . . . . 10
     5.1.  Common Mobile Access Gateway Operation . . . . . . . . . . 10
     5.2.  Common Local Mobility Anchor Operation . . . . . . . . . . 10
     5.3.  Mobility Session Created During the Runtime Assignment . . 11
       5.3.1.  General Operation  . . . . . . . . . . . . . . . . . . 11
       5.3.2.  Mobile Access Gateway Operation  . . . . . . . . . . . 12
       5.3.3.  Local Mobility Anchor Operation  . . . . . . . . . . . 13
     5.4.  Mobility Session Created After the Runtime Assignment  . . 13
       5.4.1.  General Operation  . . . . . . . . . . . . . . . . . . 14
       5.4.2.  Mobile Access Gateway Operation  . . . . . . . . . . . 14
       5.4.3.  Local Mobility Anchor Operation  . . . . . . . . . . . 15
   6.  Multi-Homing Considerations  . . . . . . . . . . . . . . . . . 16
   7.  Configuration Variables  . . . . . . . . . . . . . . . . . . . 17
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 18
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 19
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 21
     11.2. Informative References . . . . . . . . . . . . . . . . . . 21
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22
















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1.  Introduction

   This document describes the Redirect-Capability and the Redirect
   mobility options, and the corresponding functionality for a runtime
   assignment of the Local Mobility Anchor (LMA) for Proxy Mobile IPv6
   (PMIPv6).  The runtime LMA assignment takes place during a Proxy
   Binding Update (PBU) and a Proxy Binding Acknowledgement (PBA)
   messages exchange between a Mobile Access Gateway (MAG) and a LMA.
   The runtime LMA assignment functionality defined in this
   specification can be used, for example, for load balancing purposes
   during the initial PBU/PBA messages exchange.  However, other use
   cases are also possible.  In case of load balancing, the runtime LMA
   assignment approach is just one implementation option.  MAGs and LMAs
   can implement other solutions that are, for example, completely
   transparent at PMIPv6 protocol level and do not depend on the
   functionality defined in this specification.

   The runtime LMA assignment functionality described in this
   specification does not depend on information provisioned to external
   entities, such as the Domain Name System (DNS) or the Authentication,
   Authorization and Accounting (AAA) infrastructure.  The trust
   relationship and coordination management between LMAs within a PMIPv6
   domain is deployment specific and not described in this
   specification.

   There are number of reasons, why the runtime LMA assignment is an
   useful addition to the PMIPv6 protocol.  The following list describes
   some identified ones:

   o  LMAs with multiple IP addresses: a cluster of LMAs or a blade
      architecture LMA may appear to the routing system as multiple LMAs
      with separate unicast IP addresses.  A MAG can initially select
      any of those LMA IP addresses as the LMA Address using e.g., DNS-
      and AAA-based solutions.  However, MAG's initial selection may be
      suboptimal from the LMA point of view and immediate runtime
      assignment to a "proper LMA" would be needed.  The LMA could use
      [RFC5142] based approach but that would imply unnecessary setting
      up of a mobility session in a "wrong LMA" with associated backend
      support system interactions, involve additional signaling between
      the MAG and the LMA, and re-establishing mobility session to the
      new LMA again with associated signaling.

   o  Bypassing a load balancer: a cluster of LMAs or a blade
      architecture LMA may have a load balancer in front of them or
      integrated in one of the LMAs.  The load balancer would represent
      multiple LMAs during the LMA discovery phase and only its IP
      address would be exposed to the MAG hiding possible individual LMA
      or LMA blade IP addresses from the MAG.  However, if all traffic



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      must always go through the load balancer it becomes quickly a
      bottleneck.  Therefore, a PMIPv6 protocol level support for
      bypassing the load balancer after the initial PBU/PBA exchange
      would greatly help scalability.  Also bypassing the load balancer
      as soon as possible allows implementing load balancers that do not
      maintain any MN specific state information.

   o  Independence from DNS: DNS-based load balancing is a common
      practise.  However, keeping MAGs up-to-date with LMA load status
      using DNS is hard e.g., due caching and unpredictable zone update
      delays [I-D.ietf-netlmm-lma-discovery].  Generally, LMAs
      constantly updating [RFC2136] zone's master DNS server might not
      feasible in a large PMIPv6 domain due to increased load on the
      master DNS server and additional background signaling.
      Furthermore, MAGs may do (LMA) destination address selection
      decisions that are not in-line what the DNS administrator actually
      wanted [RFC3484].

   o  Independence from AAA: AAA-based solutions have basically the same
      arguments as DNS-based solutions above.  It is also typical that
      AAA-based solutions offload the initial LMA selection to the DNS
      infrastructure [RFC5779].  The AAA infrastructure does not return
      an IP address or a Fully Qualified domain Name (FQDN) to a single
      LMA, rather a FQDN representing a group of LMAs.

   o  Support for IPv6 anycast addressing [RFC4291]: the current PMIPv6
      specification does not specify how the PMIPv6 protocol should
      treat anycast addresses assigned to mobility agents.  For example,
      a blade architecture LMA may appear to the routing system as
      multiple LMAs with separate unicast IP addresses and with one or
      more "grouping" anycast addresses.  A MAG could then initially
      send a PBU to an anycast LMA address and receive a PBA from an
      anycast LMA address.  Once the MAG receives the unicast address of
      the selected r2LMA through the initial PBU/PBA exchange, the MAG
      MUST immediately start using that unicast address for the mobility
      session.















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2.  Requirements and Terminology

2.1.  Requirements

   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].

2.2.  Terminology

   In addition to the terminology defined in [RFC5213], the following
   terminology is also used:

   rfLMA

      An LMA which receives a PBU from a MAG and decides to assign an IP
      mobility session with a new target LMA (r2LMA).

   r2LMA

      The LMA assigned to a MAG as a result of the runtime LMA
      assignment.

   Runtime Assignment Domain

      A group of LMAs that consist of at least one rfLMA and one or more
      r2LMAs.  A rfLMA is allowed to assign MAGs only with r2LMAs that
      belong to the same runtime assignment domain.  The rfLMA and one
      or more r2LMAs may consist of multiple blades in a single network
      element, multiple physical network elements, or multiple LMAs
      distributed geographically.




















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3.  Proxy Mobile IPv6 Domain Assumptions

   The runtime LMA assignment functionality has several assumptions on
   the PMIPv6 domain.  They are discussed here as they have an impact on
   PMIPv6 deployment.

   Each LMA in a runtime assignment domain MUST be reachable at an
   unicast IP address.  The rfLMA and the r2LMA MUST have a prior
   agreement, adequate means to secure their inter-LMA communication and
   an established trust relationship to perform the runtime LMA
   assignment.

   The rfLMA MUST NOT assign a MAG with a r2LMA, if the rfLMA knows the
   r2LMA cannot accept a mobility session from the MAG.  That is, the
   runtime assignment functionality is not enabled in the r2LMA, or the
   r2LMA does not belong to the same runtime assignment domain as the
   rfLMA, or the r2LMA is down or otherwise unreachable.  How the rfLMA
   learns and knows the capabilities of other r2LMAs in the runtime
   assignment domain, is not covered by this specification.

   Each LMA and MAG participating to the runtime LMA assignment is
   assumed to have required Security Associations (SA) already set up in
   advance.  Dynamic negotiation of the SAs using e.g., IKEv2 [RFC5996]
   SHOULD be supported but is out of scope of this specification.

   The LMA MUST NOT include the Redirect mobility option in the PBA and
   perform the runtime LMA assignment, unless the MAG indicated the
   runtime LMA assignment functionality support in the corresponding PBU
   using the Redirection-Capability mobility option.  The LMA MUST NOT
   include the Redirect mobility option unsolicited even if the MAG had
   earlier indicated support for the runtime LMA assignment
   functionality.  MAGs and LMAs implementing the runtime LMA assignment
   functionality MUST support the runtime LMA assignment during the
   initial PBU/PBA exchange which creates a new mobility session.  A
   mid-session LMA assignment may make use of [RFC5142]
















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4.  Mobility Options

4.1.  Redirect-Capability Mobility Option

   A PBU message SHOULD contain the Redirect-Capability mobility option
   as an indication to a LMA that a MAG supports the runtime LMA
   assignment functionality.  When this option is included, the MAG may
   be assigned with another LMA, and the assigned LMA may simultaneously
   create a Binding Cache Entry (BCE).  Hence, the MAG including this
   option MUST be able to support runtime LMA assignment with and
   without a creation of a BCE in the runtime assigned LMA.  The
   Redirect-Capability mobility option has the alignment requirement of
   4n.  There can zero or one Redirect-Capability mobility option in the
   PBU.  The format of the Redirect-Capability mobility option is shown
   below:


    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 |F|        Reserved             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Redirect-Capability Mobility Option

   o  Option Type: 8-bit identifier set to TBD1.

   o  Option Length: 8-bit unsigned integer, representing the length of
      the Redirect-Capability mobility option in octets, excluding the
      Option Type and Length fields.  The Option Length MUST be set to
      2.

   o  'F' flag: This bit is set (1) if the MAG supports IPv4 transport.
      Otherwise, the bit is unset (0).

   o  Reserved: This field is reserved for future use.  MUST be set to
      zero.

4.2.  Redirect Mobility Option

   The LMA MUST include the Redirect mobility option in a PBA only if
   the MAG indicated support for the runtime LMA assignment
   functionality and runtime LMA assignment took place.  The Redirect
   mobility option in the PBA MUST contain at least one unicast address
   of the r2LMA.  There can at most one Redirect mobility option in the
   PBA.

   The Redirect mobility option has the alignment requirement of 4n.



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   The format of the Redirect mobility option is shown below:


    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 |K|N|      Reserved             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                  Optional IPv6 r2LMA Address                  |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Optional IPv4 r2LMA Address                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                         Redirect Mobility Option

   o  Option Type: 8-bit identifier set to TBD2.

   o  Option Length: 8-bit unsigned integer, representing the length of
      the Redirect mobility option in octets, excluding the Option Type
      and Length fields.  If 'K' flag is set and 'N' is unset, then the
      length MUST be 18.  If 'K' flag is unset and 'N' is set, then the
      length MUST be 6.  If both 'K' and 'N' flags are set, then the
      length MUST be 22.

   o  'K' flag: This bit is set (1) if the 'Optional IPv6 r2LMA Address'
      is included in the mobility option.  Otherwise, the bit is unset
      (0).

   o  'N' flag: This bit is set (1) if the 'Optional IPv4 r2LMA Address'
      is included in the mobility option.  Otherwise, the bit is unset
      (0).

   o  Reserved: This field is reserved for future use.  MUST be set to
      zero.

   o  Optional IPv6 r2LMA Address: the unicast IPv6 address of the
      r2LMA.  This value is present if the r2LMA IPv6 address is
      available.

   o  Optional IPv4 r2LMA Address: the IPv4 address of the r2LMA.  This
      value is present if the r2LMA IPv4 address is available and the
      'F' flag was set in the corresponding Redirect-Capability mobility
      option.




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   Both 'K' and 'N' flags MUST NOT be unset at the same time.


















































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5.  Runtime LMA Assignment

5.1.  Common Mobile Access Gateway Operation

   In the base PMIPv6 protocol [RFC5213] a MAG sends a PBU to an LMA,
   which results in a BCE creation at the LMA and the LMA sending a PBA
   sent back to the MAG.  The MAG in turn creates an entry in its
   Binding Update List (BUL).  This specification extends the base
   protocol with the runtime LMA assignment functionality.

   Backwards compatibility is maintained in a deployment wherein some
   MAGs may have the ability to support runtime LMA assignment while
   others do not.  This is accomplished by the use of the Redirect-
   Capability mobility option that a MAG includes in the PBU.  If the
   runtime LMA assignment functionality is supported and also enabled,
   then the MAG SHOULD include the Redirect-Capability mobility option
   in a PBU that establishes a new mobility session.  The Redirect-
   Capability mobility option in the PBU is also an indication to an LMA
   that the MAG supports the runtime LMA assignment functionality and is
   prepared to be assigned with a different LMA.  The runtime LMA
   assignment concerns always one mobility session at time.

   If the MAG receives a PBA that contains the Redirect mobility option
   without first including the Redirect-Capability mobility option in
   the corresponding PBU, then the MAG MUST treat the PBA as if the
   binding update failed and SHOULD log the event.

5.2.  Common Local Mobility Anchor Operation

   The text in the following sections refers to a 'LMA' when it means
   the combination of the rfLMA and the r2LMA i.e., the entity where
   runtime LMA assignment is possible.  When the text points to a
   specific LMA role during the runtime assignment, it uses either the
   'rfLMA' or the 'r2LMA'.

   If the runtime assignment functionality is enabled in the LMA but the
   LMA assignment is not going to take place for a reason or other, and
   the rfLMA is not willing to serve (or capable of) as a normal RFC
   5213 LMA for the MAG, then the rfLMA MUST reject the PBU and send
   back a PBA with Status Value set to 130 (Insufficient resources)
   error code.  Otherwise, the rfLMA MUST act as a normal RFC 5213
   defined LMA for the MAG.

   The rfLMA MUST only assign the MAG with a new r2LMA that it knows the
   MAG has a SA with or the MAG and the r2LMA are able to create it
   dynamically.  The rfLMA MUST NOT assign the MAG with a r2LMA that the
   rfLMA and the r2LMA do not have a prior agreement and an established
   trust relationship for the runtime LMA assignment.  These SA related



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   knowledge issues and trust relationships are deployment specific in a
   PMIPv6 domain and in a runtime assignment domain, and out of scope of
   this specification.  Possible context transfer and other coordination
   management between the rfLMA and the r2LMA, are again deployment
   specific for LMAs in a runtime assignment domain.

   The rfLMA MUST NOT assign a MAG using IPv6 transport with a new r2LMA
   using IPv4 transport, if the MAG does not indicate support for IPv4
   in the Redirect-Capability mobility option, as there is no guarantee
   that the MAG supports switching from IPv6 transport to IPv4
   transport.  The same also applies for assigning a MAG using IPv4
   transport with a r2LMA supporting only IPv6 transport.  If the r2LMA
   has IPv4 support enabled and the 'F' flag was set in the
   corresponding Redirect-Capability mobility option, then the PBA
   returned to the MAG SHOULD include the IPv4 address of the r2LMA in
   the Redirect mobility option even if IPv6 transport is used.

   As a result of a successful runtime LMA assignment, the PBA MUST
   contain the Redirect mobility option with a valid r2LMA Address and
   the PBA Status Value indicating success.

   In general the r2LMA may be a normal RFC 5213 LMA without any runtime
   LMA assignment functionality.  The r2LMA MAY also include rfLMA
   functionality in which case the consideration described in the
   following sections for the rfLMA apply.  If the runtime LMA
   assignment functionality is implemented but not enabled in a LMA,
   then the LMA MUST ignore the Redirect-Capability mobility option
   received in PBUs and act as a LMA defined in RFC 5213.

5.3.  Mobility Session Created During the Runtime Assignment

5.3.1.  General Operation

   During the runtime LMA assignment, the PBA is returned from the LMA
   Address where the PBU was sent to i.e., from the rfLMA.  After the
   runtime LMA assignment all PMIPv6 communication continues directly
   between the MAG and the r2LMA.  The overall runtime LMA assignment
   flow sequence is shown in Figure 1.













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     MAG     rfLMA    r2LMA
      |        |        |
   1) |--PBU-->|  ~ ~ ~ | (LMA assignment takes place, BCE gets created
   2) |<--PBA--| ~ ~ ~  |  in r2LMA, PBA contains r2LMA information and
      |        |        |  Status Value set to
      |        |        |  Accepted_and_Redirected_with_Binding)
   3) |<=====data======>|
      |        |        |
   4) |-------PBU------>| (lifetime extension,
   5) |<------PBA-------|  de-registration, etc.)
      |        |        |

   Figure 1: Runtime LMA assignment from rfLMA to r2LMA and setting up a
     mobility session in the r2LMA within a runtime assignment domain

   The assumption in the signaling flow step 1) shown in Figure 1 is
   that the mobility session gets created in the r2LMA, although the
   rfLMA is responsible for interfacing with the MAG.  The interaction
   between the rfLMA and the r2LMA in the runtime assignment domain is
   not defined in this specification.  There are several possible
   solutions for the rfLMA and the r2LMA interaction depending on e.g.
   the collocation properties of the rfLMA and the r2LMA, and whether
   the rfLMA and the r2LMA just use base PMIPv6 protocol between each
   other.

5.3.2.  Mobile Access Gateway Operation

   In addition to MAG operations described in Section 5.1, the following
   considerations has to taken into account during the runtime LMA
   assignment.

   If the MAG receives a PBA that contains the Redirect mobility option
   and the Status Value set to TBD3
   (Accepted_and_Redirected_with_Binding), and the MAG had included the
   Redirect-Capability mobility option in the corresponding PBU, then
   the MAG MUST perform the following steps in addition to the normal
   RFC 5213 PBA processing:

   o  If there is no SA between the MAG and the r2LMA, the MAG MAY treat
      the PBA as if the binding update failed and log the event.  The
      MAG SHOULD initiate a dynamic creation of the SA between the MAG
      and the r2LMA (note that the dynamic creation of the SA is outside
      of the scope of this specification).

   If the runtime LMA assignment was successful, the MAG updates the BUL
   to correspond the r2LMA Address included in the received Redirect
   mobility option.  There is no need to resend any PBUs to the r2LMA
   after a successful runtime assignment.  The mobility session has



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   already been established in the r2LMA as indicated by the Status
   Value TBD3 (Accepted_and_Redirected_with_Binding).  The MAG MUST send
   subsequent binding refreshing PBUs and user traffic to the new r2LMA
   Address.

5.3.3.  Local Mobility Anchor Operation

   If the runtime LMA assignment functionality is enabled in the LMA and
   the received PBU contains the Redirect-Capability mobility option,
   then the rfLMA MAY assign the MAG with a new r2LMA.  In the case of
   runtime LMA assignment, the PBA returned to the MAG MUST always
   include the unicast IP address (IPv6, IPv4 or both) of the r2LMA in
   the Redirect mobility option and the Status Value set to TBD3
   (Accepted_and_Redirected_with_Binding).  If the rfLMA did not assign
   the MAG with a new r2LMA or the runtime LMA assignment failed, then
   the PBA MUST NOT contain the Redirect mobility option.

   If the runtime LMA assignment was successful, the mobility session
   MUST be established in the r2LMA.  The actual PBU processing that
   creates the mobility session and the corresponding BCE takes place in
   the r2LMA.  However, depending on the LMA's implementation of the
   PMIPv6 security framework, the security processing (such as IPsec) of
   the PBU may take place in the rfLMA before the PBU is transferred
   from the rfLMA to the r2LMA.  Whenever the runtime assignment
   processing has involved the r2LMA, the PBA sent by the rfLMA to the
   MAG MUST reflect the information the r2LMA would include in its PBA
   (such as mobility options, Status Value and so on).  The only
   exceptions are possible security related options that the rfLMA MAY
   need to modify or remove.  The rfLMA is always allowed to add more
   mobility options to the PBA.

   During the runtime LMA assignment process, the rfLMA MAY need to
   maintain a temporary MAG-rfLMA-r2LMA state and may even act as a
   "proxy MAG" to the r2LMA.  This, however, depends on the collocation
   properties of the rfLMA and the r2LMA, and how the rfLMA interact
   with the r2LMA.  The interaction may happen as a PBU/PBA packet
   forwarding/proxying in a conventional sense or as an inter-blade
   communication using some LMA architecture specific communication
   method.  Once the runtime LMA assignment has completed successfully
   from the rfLMA point of view and it has sent the PBA to the MAG, the
   rfLMA can remove all state information regarding the recent runtime
   LMA assignment.

5.4.  Mobility Session Created After the Runtime Assignment







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5.4.1.  General Operation

   During the runtime LMA assignment the PBA is returned from the LMA
   Address where the PBU was sent to i.e., from the rfLMA.  After the
   runtime LMA assignment, the MAG has to initiate another PBU/PBA
   exchange with the r2LMA and after that all PMIPv6 communication
   continues between the MAG and the r2LMA.  The overall runtime LMA
   assignment flow sequence is shown in Figure 2.


     MAG     rfLMA    r2LMA
      |        |        |
   1) |--PBU-->|        | (assignment takes place, PBA contain
   2) |<--PBA--|        |  r2LMA information, Status Value set
      |        |        |  to Rejected_but_Redirected)
      |        |        |
   3) |-------PBU------>| (BCE gets created in r2LMA)
   4) |<------PBA-------|
      |        |        |
   5) |<=====data======>|
      |        |        |
   6) |-------PBU------>| (lifetime extension,
   7) |<------PBA-------|  de-registration, etc.)
      |        |        |

   Figure 2: Runtime LMA assignment from rfLMA to r2LMA within a runtime
                             assignment domain

   The assumption in the signaling flow steps 1) and 2) shown in
   Figure 2 is that the MAG is only assigned with the r2LMA.  The
   mobility session creation with the r2LMA requires a new PBU/PBA
   exchange with the r2LMA using the normal RFC 5213 procedures.

5.4.2.  Mobile Access Gateway Operation

   The MAG operation is exactly the same as described in Section 5.1 and
   Section 5.3.2 except for two aspects:

   o  The Status Value in the received PBA is set to TBD4
      (Rejected_but_Redirected).  This indicates to the MAG that there
      is no mobility session (i.e.  BCE) created in the r2LMA and not in
      the rfLMA either.  The MAG was only assigned with a new r2LMA
      Address information.

   o  The MAG MUST initiate a new PBU/PBA exchange with the r2LMA in
      order to establish a mobility session.  Only after a successful
      PBU/PBA exchange with the r2LMA, the runtime assignment has
      completed.  The initial PBU sent to the r2LMA SHOULD NOT contain



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      the Redirect-Capability mobility option in order to avoid possible
      immediate new runtime LMA assignment.

5.4.3.  Local Mobility Anchor Operation

   If the runtime LMA assignment functionality is enabled in the LMA and
   the received PBU contains the Redirect-Capability mobility option,
   then the rfLMA MAY assign the MAG with a new r2LMA.  In the case of
   runtime LMA assignment, the PBA returned to the MAG MUST always
   include the unicast IP address (IPv6, IPv4 or both) of the r2LMA in
   the Redirect mobility option and the Status Value set to TBD4
   (Rejected_but_Redirected).  If the rfLMA did not assign the MAG with
   a new r2LMA or the runtime assignment failed, then the PBA MUST NOT
   contain the Redirect mobility option and the PBA is processed
   according to RFC 5213.




































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6.  Multi-Homing Considerations

   A MN can be multi-homed.  A single LMA entity should have the control
   over all possible multi-homed mobility sessions the MN has.  All
   mobility sessions a multi-homed MN may have SHOULD be anchored in the
   single LMA entity.  Therefore, once the MN has established one
   mobility session with one LMA, the subsequent mobility sessions of
   the same MN SHOULD be anchored to the LMA that was initially
   assigned.

   One possible solution already supported by this specification is
   applying the runtime LMA assignment only for the very first initial
   attach a multi-homed MN does towards a PMIPv6 domain.  After the
   initial attach, the assigned r2LMA Address has been stored in the
   policy profile.  For the subsequent mobility sessions of the multi-
   homed MN, the same assigned r2LMA Address would be used and there is
   no need to contact the rfLMA.

   MAGs have a control over selectively enabling and disabling the
   runtime assignment of the LMA.  If the multi-homed MN is attached to
   a PMIPv6 domain via multiple MAGs, the assigned r2LMA Address should
   be stored in the remote policy store and downloaded as a part of the
   policy profile download to a MAG.  Alternatively, MAGs can share
   policy profile information using other means.  In both cases, the
   actual implementation of the policy profile information sharing is
   specific to a PMIPv6 deployment and out of scope of this
   specification.
























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7.  Configuration Variables

   This specification defines three configuration variables that control
   the runtime LMA assignment functionality within a PMIPv6 domain.

   EnableLMARedirectFunction

      This configuration variable is available in both a MAG and in a
      rfLMA.  When set to TRUE (i.e., enabled), the PMIPv6 node enables
      the runtime LMA assignment functionality.  The default value is
      FALSE (i.e., disabled).

   EnableLMARedirectAcceptFunction

      This configuration variable is available in a r2LMA.  When set to
      TRUE (i.e., enabled), the r2LMA is able to accept runtime LMA
      assignment mobility sessions from a rfLMA.  The default value is
      FALSE (i.e., disabled).

































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8.  Security Considerations

   The security considerations of PMIPv6 signaling described in RFC 5213
   apply to this document.  An incorrectly configured LMA may cause
   unwanted runtime LMA assignment attempts to non-existing LMAs or to
   other LMAs that do not have and will not have a SA with the MAG.
   Consequently, the MAG will experience failed binding updates or
   unsuccessful creation of mobility sessions.  An incorrectly
   configured LMA may also cause biased load distribution within a
   PMIPv6 domain.  This document also assumes that the LMAs that
   participate to runtime LMA assignment have adequate prior agreement
   and trust relationship between each other.

   If the SAs between MAGs and LMAs are manually keyed (as it may be
   needed by the scenario described in Section 5.3), then the anti-
   replay service of ESP protected PMIPv6 traffic cannot typically be
   provided.  This is, however, deployment specific to a PMIPv6 domain.

   If a PMIPv6 domain deployment with a runtime LMA assignment requires
   that a rfLMA has to modify a PBU/PBA in any way e.g., by changing the
   source and destination IP address or any other field of the
   encapsulating IP packet, then the security mechanism (such as
   possible authentication options) used to protect the PBU/PBA MUST NOT
   cover the outer IP packet on those parts that might get modified.
   Alternatively, the rfLMA can do all required security processing on
   the PBU/PBA, and the communication between the rfLMA and the r2LMA
   would be unprotected at the PMIPv6 protocol level.  In this case the
   runtime assignment domain MUST implement adequate level of security
   using other means, such as layer-2 VPNs.






















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9.  IANA Considerations

   Two new mobility options for the use with PMIPv6 are defined in the
   [RFC3775] "Mobility Options" registry.  The mobility options are
   defined in Section 4:

       Redirect-Capability Mobility Option   is set to TBD1
       Redirect Mobility Option              is set to TBD2

   This document defines the following new Status values for use in PBA
   messages.  The values are to be allocated from the same number space,
   as defined in Section 6.1.8 of [RFC3775].

   The value below MUST be less than 128 indicating that the PBU was
   accepted by the LMA:

       Accepted_and_Redirected_with_Binding  is set to TBD3

   The value below MUST be greater than 128 indicating that the PBU was
   rejected by the LMA:

       Rejected_but_Redirected               is set to TBD4





























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10.  Acknowledgements

   The author would like to thank Basavaraj Patil, Domagoj Premec, Ahmad
   Muhanna, Vijay Devarapalli and Qin Wu for their reviews and comments
   on this document.  The authors also thank Yungui Wang for his
   comments and discussion on this document.













































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11.  References

11.1.  Normative References

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

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

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

11.2.  Informative References

   [I-D.ietf-netlmm-lma-discovery]
              Korhonen, J. and V. Devarapalli, "LMA Discovery for Proxy
              Mobile IPv6", draft-ietf-netlmm-lma-discovery-06 (work in
              progress), September 2010.

   [RFC2136]  Vixie, P., Thomson, S., Rekhter, Y., and J. Bound,
              "Dynamic Updates in the Domain Name System (DNS UPDATE)",
              RFC 2136, April 1997.

   [RFC3484]  Draves, R., "Default Address Selection for Internet
              Protocol version 6 (IPv6)", RFC 3484, February 2003.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.

   [RFC5142]  Haley, B., Devarapalli, V., Deng, H., and J. Kempf,
              "Mobility Header Home Agent Switch Message", RFC 5142,
              January 2008.

   [RFC5779]  Korhonen, J., Bournelle, J., Chowdhury, K., Muhanna, A.,
              and U. Meyer, "Diameter Proxy Mobile IPv6: Mobile Access
              Gateway and Local Mobility Anchor Interaction with
              Diameter Server", RFC 5779, February 2010.

   [RFC5996]  Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
              "Internet Key Exchange Protocol Version 2 (IKEv2)",
              RFC 5996, September 2010.









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Authors' Addresses

   Jouni Korhonen (editor)
   Nokia Siemens Networks
   Linnoitustie 6
   FI-02600 Espoo
   FINLAND

   Email: jouni.nospam@gmail.com


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

   Email: sri.gundavelli@cisco.com


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

   Email: yokota@kddilabs.jp


   Xiangsong Cui
   Huawei Technologies
   KuiKe Bld., No.9 Xinxi Rd.
   Shang-Di Information Industry Base
   Hai-Dian District, Beijing, P.R. China, 100085

   Email: Xiangsong.Cui@huawei.com















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