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Distributed Mobility Anchoring
draft-chan-dmm-distributed-mobility-anchoring-07

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This is an older version of an Internet-Draft whose latest revision state is "Replaced".
Authors Anthony Chan , Xinpeng Wei , Jong-Hyouk Lee , Seil Jeon , Fred Templin
Last updated 2016-03-18
Replaced by draft-ietf-dmm-distributed-mobility-anchoring, RFC 8818
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draft-chan-dmm-distributed-mobility-anchoring-07
DMM                                                              H. Chan
Internet-Draft                                                    X. Wei
Intended status: Informational                       Huawei Technologies
Expires: September 20, 2016                                       J. Lee
                                                    Sangmyung University
                                                                 S. Jeon
                                           Instituto de Telecomunicacoes
                                                              F. Templin
                                          Boeing Research and Technology
                                                          March 19, 2016

                     Distributed Mobility Anchoring
            draft-chan-dmm-distributed-mobility-anchoring-07

Abstract

   This document defines distributed mobility anchoring.  Multiple
   anchors and nodes are configured with appropriate mobility functions
   and work together to enable mobility solutions.  Example solution is
   mid-session switching of the IP prefix anchor.  Without ongoing
   session requiring session continuity, a flow can be started or re-
   started using the new IP prefix which is allocated from the new
   network and is therefore anchored to the new network.  With ongoing
   session, the anchoring of the prior IP prefix may be relocated to the
   new network to enable session continuity.

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 September 20, 2016.

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Copyright Notice

   Copyright (c) 2016 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
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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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Terminology . . . . . . . . . . . . . . . . .   3
   3.  Distributed anchoring . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Distributed anchoring configurations  . . . . . . . . . .   5
     3.2.  Distributed anchoring behaviors and message information
           elements  . . . . . . . . . . . . . . . . . . . . . . . .   8
       3.2.1.  Location management behaviors and message information
               elements  . . . . . . . . . . . . . . . . . . . . . .   8
       3.2.2.  Forwarding management behaviors and message
               information elements  . . . . . . . . . . . . . . . .   9
   4.  Example mobility solutions with distributed anchoring . . . .  11
     4.1.  IP mobility support only when needed  . . . . . . . . . .  11
       4.1.1.  Not needed: Changing to the new IP prefix/address . .  12
       4.1.2.  Needed: Providing IP mobility support . . . . . . . .  13
     4.2.  IP prefix/address anchor switching to the new network . .  15
       4.2.1.  Centralized control plane . . . . . . . . . . . . . .  16
       4.2.2.  Hierarchical network  . . . . . . . . . . . . . . . .  19
       4.2.3.  Hierarchical network with anchoring change  . . . . .  21
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  22
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  23
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  23
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  23
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  23
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  25
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  25

1.  Introduction

   A key requirement in distributed mobility management [RFC7333] is to
   enable traffic to avoid traversing single mobility anchor far from
   the optimal route.  Distributed mobility management solutions do not

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   make use of centrally deployed mobility anchor
   [Paper-Distributed.Mobility].  As such, the traffic of a flow SHOULD
   be able to change from traversing one mobility anchor to traversing
   another mobility anchor as the mobile node moves, or when changing
   operation and management requirements call for mobility anchor
   switching, thus avoiding non-optimal routes.  This draft proposes
   distributed mobility anchoring to enable making such route changes.

   Distributed mobility anchoring employs multiple anchors in the data
   plane.  In general, the control plane function may co-located with
   the data plane function at these distributed anchors but may also be
   separate from the data plane functions and be centralized.  Different
   configurations (Section 3.1) of distributed anchoring are then
   possible.  Yet the distributed anchors need to have expected
   behaviors (Section 3.2).

   A mobile node (MN) attached to an access router of a network may be
   allocated an IP prefix which is anchored to that router.  It may then
   use the IP address configured from this prefix as the source IP
   address to run a flow with its correspondent node (CN).  When there
   are multiple anchors, the flow may need to select the anchor when it
   is initiated (Section 4).  Using an anchor in MN's network of
   attachment has the advantage that the packets can simply be forwarded
   according to the forwarding table.  Although the anchor is in the
   MN's network of attachment when the flow was initiated, the MN may
   later move another network, so that the IP address no longer belongs
   to the new network of attachment of the MN.  Whether the flow needs
   session continuity will determine how to ensure that the IP address
   of the flow will be anchored to the new network of attachment.  If
   the ongoing IP flow can cope with an IP prefix/address change, the
   flow can be reiniated with a new IP address anchored in the new
   network (Section 4.1.1).  On the other hand, if the ongoing IP flow
   cannot cope with such change, the IP address anchoring can be
   relocated from the original network to the new network (Section 4.2).

2.  Conventions and Terminology

   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].

   All general mobility-related terms and their acronyms used in this
   document are to be interpreted as defined in the Mobile IPv6 base
   specification [RFC6275], the Proxy Mobile IPv6 specification
   [RFC5213], and the DMM current practices and gap analysis [RFC7429].
   This includes terms such as mobile node (MN), correspondent node
   (CN), home agent (HA), home address (HoA), care-of-address (CoA),
   local mobility anchor (LMA), and mobile access gateway (MAG).

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   In addition, this document uses the following term:

   Home network of an application session (or of an HoA):  the network
      that has allocated the IP address (HoA) used for the session
      identifier by the application running in an MN.  An MN may be
      running multiple application sessions, and each of these sessions
      can have a different home network.

   IP prefix/address anchoring:  An IP prefix, i.e., Home Network Prefix
      (HNP), or address, i.e., Home Address (HoA), allocated to a mobile
      node is topologically anchored to a node when the anchor node is
      able to advertise a connected route into the routing
      infrastructure for the allocated IP prefix.

   Internetwork Location Management (LM) function:  managing and keeping
      track of the internetwork location of an MN.  The location
      information may be a binding of the IP advertised address/prefix,
      e.g., HoA or HNP, to the IP routing address of the MN or of a node
      that can forward packets destined to the MN.  It is a control
      plane function.

      In a client-server protocol model, location query and update
      messages may be exchanged between a Location Management client
      (LMc) and a Location Management server (LMs).

      With separation of control plane and data plane, the LM function
      is in the control plane.  It may be a logical function at the
      control plane node, control plane anchor, or mobility controller.

      It may be distributed or centralized.

   Forwarding Management (FM) function:  packet interception and
      forwarding to/from the IP address/prefix assigned to the MN, based
      on the internetwork location information, either to the
      destination or to some other network element that knows how to
      forward the packets to their destination.

      This function may be used to achieve indirection.  With separation
      of control plane and data plane, FM may split into a FM function
      in the data plane (FM-DP) and a FM function in the control plane
      (FM-CP).

      FM-DP may be distributed with distributed mobility management.  It
      may be a function in a data plane anchor or data plane node.

      FM-CP may be distributed or centralized.  It may be a function in
      a control plane node, control plane anchor or mobility controller.

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   Security Management (SM) function:  The security management function
      controls security mechanisms/protocols providing access control,
      integrity, authentication, authorization, confidentiality, etc.
      for the control plane and data plane.

      This function resides in all nodes such as control plane anchor,
      data plane anchor, mobile node, and correspondent node.

3.  Distributed anchoring

3.1.  Distributed anchoring configurations

   The mobility functions may be implemented in different configurations
   of distributed anchoring.  Some of these configurations are described
   in [I-D.sijeon-dmm-deployment-models].

   Figure 1 shows 4 configurations.  In each configuration, an MN is
   allocated an IP prefix/address IP1 and is using IP1 to communicate
   with a correspondent node (CN) not shown in the figure.  The flow of
   this communication session is shown as flow(IP1, ...) which uses IP1
   and other parameters.  The IP1 is anchored to the data plane anchor
   (DPA) which has IP prefix/address IPa1.  The data plane is
   distributed so that there may be multiple instances of the DPA (not
   shown).  The control plane may either be distributed or centralized.
   When the control plane anchor (CPA) co-locates with the distributed
   DPA there will be multiple instances of the co-located CPA and DPA
   (not shown).

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       (a)                (b)                (c)                (d)
                           +-----+                               +-----+
                           |LMs  |                               |LMs  |
                           +-----+                               +-----+

 +------------+     +------------+     +------------+     +------------+
 |CPA:        |     |CPA:        |     |CPA:        |     |CPA:        |
 |FM-CP, LM   |     |FM-CP, LMc  |     |FM-CP, LMs  |     |FM-CP, LMp  |
 +------------+     +------------+     +------------+     +------------+
 +------------+     +------------+     +------------+     +------------+
 |DPA(IPa1):  |     |DPA(IPa1):  |     |DPA(IPa1):  |     |DPA(IPa1):  |
 |anchors IP1 |     |anchors IP1 |     |anchors IP1 |     |anchors IP1 |
 |FM-DP       |     |FM-DP       |     |FM-DP       |     |FM-DP       |
 +------------+     +------------+     +------------+     +------------+

                                       +------------+     +------------+
                                       |CPN:        |     |CPN:        |
                                       |FM-CP, LMc  |     |FM-CP, LMc  |
                                       +------------+     +------------+
                                       +------------+     +------------+
                                       |DPN(IPn1):  |     |DPN(IPn1):  |
                                       |FM-DP       |     |FM-DP       |
                                       +------------+     +------------+

 +------------+     +------------+     +------------+     +------------+
 |MN(IP1)     |     |MN(IP1)     |     |MN(IP1)     |     |MN(IP1)     |
 |flow(IP1,..)|     |flow(IP1,..)|     |flow(IP1,..)|     |flow(IP1,..)|
 +------------+     +------------+     +------------+     +------------+

   Figure 1.  (a) FM-CP and LM at CPA, FM-DP at DPA; (b) Separate LMs,
   FM-CP and LMc at CPA, FM-DP at DPA; (c) FM-CP and LMs at CPA, FM-DP
   at DPA, FM-CP and LMc at CPN, FM-DP at DPN; (d) Separate LMs, FM-CP
   and LMp at CPA, FM-DP at DPA, FM-CP and LMc at CPN, FM-DP at DPN.

   In Figure 1(a), both LM and FM co-locate at the anchor.  FM-DP is at
   the DPA whereas LM and FM-CP are at the CPA.  Then LM may be
   distributed or centralized according to whether the CPA is
   distributed or centralized.

   Figure 1(b) differs from Figure 1(a) in that the LM function is split
   into a server LMs and a client LMc.  FM-DP is at the DPA whereas LMc
   and FM-CP are at the CPA.  The LMs may be centralized whereas the LMc
   may be distributed or centralized according to whether the CPA is
   distributed or centralized.

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   In Figure 1(c), FM-DP is at DPA whereas LMs and FM-CP are at the CPA.
   In addition, there is also FM-DP at a data plane node (DPN), and
   there are also FM-CP together with LMc at a control plane node (CPN).
   In the hierarchy, there may be multiple DPN's for each DPA.  Again,
   LMs may be distributed or centralized according to whether the CPA is
   distributed or centralized.  The DPA may co-locate with CPA or may be
   separated.  When separation of data plane and control plane, DPA may
   be distributed when CPA is centralized.

   Figure 1(d) differs from Figure 1(c) in that the LMs is separated
   out, and a proxy LMp is added between the LMs and LMc.  FM-DP is at
   the DPA whereas LMp and FM-CP are at the CPA.  Again, there is also
   FM-DP at a data plane node (DPN), and there are also FM-CP together
   with LMc at a control plane node (CPN).  The FMs may be centralized
   whereas the LMp may be distributed or centralized according to
   whether the CPA is distributed or centralized.

   A host-based variant of the mobility function configuration from
   Figure 1(c) and 1(d) is shown in Figure 2(a) and 2(b).

         (a)                (b)
                             +-----+
                             |LMs  |
                             +-----+

   +------------+     +------------+
   |CPA:        |     |CPA:        |
   |FM-CP, LMs  |     |FM-CP, LMp  |
   +------------+     +------------+
   +------------+     +------------+
   |DPA(IPa1):  |     |DPA(IPa1):  |
   |anchors IP1 |     |anchors IP1 |
   |FM-DP       |     |FM-DP       |
   +------------+     +------------+

   +------------+     +------------+
   |MN(IP1)     |     |MN(IP1)     |
   |flow(IP1,..)|     |flow(IP1,..)|
   |FM,    LMc  |     |FM,    LMc  |
   +------------+     +------------+

   Figure 2.  (a) FM-CP and LMs at CPA, FM-DP at DPA, FM and LMc at MN;
   (b) Separate LMs, FM-CP and LMp at CPA, FM-DP at DPA, FM and LMc at
   MN.

   In Figure 2(a), FM-DP is at DPA whereas LMs and FM-CP are at the CPA.
   In addition, there is FM and LMc at the MN.  The LMs may be

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   distributed or centralized according to whether the CPA is
   distributed or centralized.

   Figure 2(b) differs from Figure 2(a) in that the LMs is separated out
   and a proxy is added between the LMs and LMc.  FM-DP is at the DPA
   whereas LMp and FM-CP are at the CPA.  In addition, there is FM and
   LMc at the MN.  The FMs may be centralized whereas the LMp may be
   distributed or centralized according to whether the CPA is
   distributed or centralized.

3.2.  Distributed anchoring behaviors and message information elements

   The behaviors of distributed anchoring are defined in this section in
   order that they may work together in expected manners to produce a
   distributed mobility solution.  The needed information elements are
   passed as message parameters.

3.2.1.  Location management behaviors and message information elements

   It is seen in (Section 3.1) that

   (1)  LMs may be a separate server or may co-locate with CPA;
   (2)  LMc may be at CPA, CPN, or MN.

   Example LM design may consists of a distributed database of LMs
   servers in a pool of distributed servers.  The prefix of a MN is
   hosted at a given LMs as the primary location information for this
   prefix.  Peer LMs may exchange the location information with each
   other.  LMc may retrieve a given record or send a given update record
   to LMs.

   Location information bebaviors:

   (LM:1)  LMc queries LMs about location information for a prefix of MN
           (pull).
           Parameters:
           IP prefix of MN.

   (LM:2)  LMs replies to LMc query about location information for a
           prefix of MN (pull).
           Parameters:
           IP prefix of MN,
           IP address of FM-DP/DPA/DPN to forward the packets of the
           flow.

   (LM:3)  LMs informs LMc about location information for a prefix of MN
           (push).
           Parameters:

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           IP prefix of MN,
           IP address of FM-DP/DPA/DPN to forward the packets of the
           flow.

   (LM:4)  LMs joins a LMs pool.
           Parameters:
           IP address of the LMs,
           IP prefixes for which the LMs will host the primary location
           information.

   (LM:5)  LMs queries a peer LMs about location information for a
           prefix of MN.
           Parameters:
           IP prefix.

   (LM:6)  LMs replies to a peer LMs about location information for a
           prefix of MN (push).
           Parameters:
           IP prefix of MN,
           IP address of FM-DP/DPA/DPN to forward the packets of the
           flow.

3.2.2.  Forwarding management behaviors and message information elements

   It is seen in (Section 3.1) that

   (1)  FM-CP may be at CPA, CPN, MN;
   (2)  FM-DP may be at DPA, DPN, MN.

   The FM behaviors and message information elements are:

   (FM:1)  An anchor acts on packets on a per flow basis and performs
           the changes to the forwarding path upon a change of point of
           attachment of a MN:

           (FM:1-1)  FM filters the packets up to the granularity of a
                     flow.
                     Example matching parameters are the 5-tuple of a
                     flow.

           (FM:1-2)  FM makes the necessary changes to the forwarding
                     path of a flow.
                     Example mechanism is through forwarding table
                     update activated by DHCPv6-PD.

           (FM:1-3)  FM reverts the previously made changes to the
                     forwarding path of a flow when such changes are no

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                     longer needed, e.g., when an ongoing flow requiring
                     session continuity has closed.
                     Example mechanism is through expiration of
                     DHCPv6-PD.

   (FM:2)  An anchor may discover and be discovered such as through an
           anchor registration system:

           (FM:2-1)  FM registers and authenticates itself with a
                     centralized mobility controller.
                     Parameters:
                     IP address of DPA and its CPA;
                     IP prefix anchored to the DPA.

           (FM:2-2)  registration reply: acknowledge of registration and
                     echo the input parameters.

           (FM:2-3)  FM discovers the FM of another IP prefix by
                     querying the mobility controller based on the IP
                     prefix.
                     Parameters:
                     IP prefix of MN.

           (FM:2-4)  when making anchor discovery FM expects the answer
                     parameters as: IP address of DPA to which IP prefix
                     of MN is anchored; IP prefix of the corresponding
                     CPA.

   (FM:3)  With separation of control plane function and data plane
           function, these function must work together.

           (FM:3-1)  CPA/FM-CP sends forwarding table updates to DPA/FM-
                     DP.
                     Parameters:
                     new forwarding table entries to add;
                     expired forwarding table entries to delete.

           (FM:3-2)  DPA/FM-DP sends to CPA/FM-CP about its status and
                     load.
                     Parameters:
                     state of forwarding function being active or not;
                     loading percentage.

   (FM:4)  An anchor can buffer packets of a flow in a mobility event:

           (FM:4-1)  CPA/FM-CP informs DPA/FM-DP to buffer packets of a
                     flow.
                     Trigger:

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                     MN leaves DPA in a mobility event.
                     Parameters:
                     IP prefix of the flow for which packets need to be
                     buffered.

           (FM:4-2)  CPA/FM-CP on behalf of a new DPA/FM-DP informs CPA/
                     FM-CP of the prior DPA/FM-DP that it is ready to
                     receive any buffered packets of a flow.
                     Parameters:
                     destination IP prefix of the flow's packets;
                     IP address of the new DPA.

4.  Example mobility solutions with distributed anchoring

   The IP prefix/address at the MN's side of a flow may be anchored at
   the access router to which the MN is attached.  For example, when an
   MN attaches to a network (Net1) or moves to a new network (Net2), it
   is allocated an IP prefix from that network.  It configures from this
   prefix an IP address which is typically a dynamic IP address.  It
   then uses this IP address when a flow is initiated.  Packets to the
   MN in this flow are simply forwarded according to the forwarding
   table.

   There may be multiple IP prefixes/addresses to choose from.  They may
   be from the same access network or different access networks.  The
   network may advertise these prefixes with cost options
   [I-D.mccann-dmm-prefixcost] so that the mobile node may choose the
   one with the least cost.  In addition, these IP prefixes/addresses
   may be of different types regarding whether mobility support is
   needed [I-D.dmm-ondemand-mobility-api].  A flow will need to choose
   the appropriate one according to whether it needs IP mobility
   support.

4.1.  IP mobility support only when needed

   IP mobility support may be provided only when needed instead of being
   provided by default.  The simplest configuration in this case is
   shown in Figures 1(a) and 1(b) in Section 3.1 for which the LM and FM
   functions are utilized only when needed.

   A straightforward choice of mobility anchoring is for a flow to use
   the IP prefix of the network to which the MN is attached when the
   flow is initiated [I-D.seite-dmm-dma].

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4.1.1.  Not needed: Changing to the new IP prefix/address

   When IP mobility support is not needed for a flow, the LM and FM
   functions are not utilized so that the configuration from Figures
   1(a) and 1(b) in Section 3.1 simplifies to that shown in Figure 3.

Net1                                                   Net2

+---------------+                                      +---------------+
|AR1            |                                      |AR2            |
+---------------+                                      +---------------+
|CPA:           |                                      |CPA:           |
|---------------|                                      |---------------|
|DPA(IPa1):     |                                      |DPA(IPa2):     |
|anchors IP1    |                                      |anchors IP2    |
+---------------+                                      +---------------+

+...............+                                      +---------------+
.MN(IP1)        .                 move                 |MN(IP2)        |
.flow(IP1,...)  .               =======>               |flow(IP2,...)  |
+...............+                                      +---------------+

   Figure 3.  Changing to the new IP prefix/address.  MN running a flow
   using IP1 in Net1 changes to running a flow using IP2 in Net2.

   When there is no need to provide IP mobility to a flow, the flow may
   use a new IP address acquired from a new network as the MN moves to
   the new network.

   Regardless of whether IP mobility is needed, if the flow has
   terminated before the MN moves to a new network, the flow may
   subsequently restart using the new IP address allocated from the new
   network.

   When session continuity is needed, even if a flow is ongoing as the
   MN moves, it may still be desirable for the flow to change to using
   the new IP prefix configured in the new network.  The flow may then
   close and then restart using a new IP address configured in the new
   network.  Such a change in the IP address of the flow may be enabled
   using a higher layer mobility support which is not in the scope of
   this document.

   In Figure 3, a flow initiated while the MN was in Net1 has terminated
   before the MN moves to a new network Net2.  After moving to Net2, the
   MN uses the new IP prefix anchored in Net2 to start a new flow.  The
   packets may then be forwarded without requiring IP layer mobility
   support.

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   The call flow is outlined in Figure 4.

 MN                    p-AR          n-AR                             CN
  |MN attaches to p-AR: |             |                                |
  |acquire MN-ID and profile          |                                |
  |--RS---------------->|             |                                |
  |                     |             |                                |
  |<----------RA(HNP1)--|             |                                |
  |                     |             |                                |
Allocated prefix HNP1
IP1 address configuration
  |                     |             |                                |
  |<-Flow(IP1,IPcn,...)-+--------------------------------------------->|
  |                     |             |                                |
  |MN detaches from p-AR|             |                                |
  |MN attaches to n-AR  |             |                                |
  |                     |             |                                |
  |--RS------------------------------>|                                |
  |                     |             |                                |
  |<--------------RA(HNP2)------------|                                |
  |                     |             |                                |
Allocated prefix HNP2
IP2 address configuration
  |                     |             |                                |
  |<-new Flow(IP2,IPcn,...)-----------+------------------------------->|
  |                     |             |                                |

   Figure 4.  A flow uses the IP allocated from the network at which the
   MN is attached when the flow is initiated.

   The security management function in the anchor node at a new network
   must allow to assign a valid IP prefix/address to a mobile node.

4.1.2.  Needed: Providing IP mobility support

   When IP mobility is needed for a flow, the LM and FM functions in
   Figures 1(a) and 1(b) in Section 3.1 are utilized.  The mobility
   support may be provided by IP prefix anchor switching to the new
   network to be described in Section 4.2 or by using other mobility
   management methods ([Paper-Distributed.Mobility.PMIP] and
   [Paper-Distributed.Mobility.Review]).  Then the flow may continue to
   use the IP prefix from the prior network.  Yet some time later, the
   user application for the flow may be closed.  If the application is
   started again, the new flow may not need to use the prior network's
   IP address to avoid having to invoke IP mobility support.  This may
   be the case where a permanent IP prefix/address is not used.  The
   flow may then use the new IP prefix in the network where the flow is

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   being initiated.  Routing is again kept simpler without employing IP
   mobility and will remain so as long as the MN has not moved away from
   that network.

   The call flow in this case is outlined in Figure 5.

 MN                    p-AR          n-AR                             CN
  |MN attaches to p-AR: |             |                                |
  |acquire MN-ID and profile          |                                |
  |--RS---------------->|             |                                |
  |                     |             |                                |
  |<----------RA(HNP1)--|             |                                |
  |                     |             |                                |
Allocated prefix HNP1
IP1 address configuration
  |                     |             |                                |
  |<-Flow(IP1,IPcn,...)-+--------------------------------------------->|
  |                     |             |                                |
  |MN detach from p-AR  |             |                                |
  |MN attach to n-AR    |             |                                |
  |                     |             |                                |
  |--RS------------------------------>|                                |

IP mobility support such as that described in next sub-section
  |<--------------RA(HNP2,HNP1)-------|                                |
  |                     |             |                                |
  |<-Flow(IP1,IPcn,...)---------------+------------------------------->|
  |                     |             |                                |
Allocated prefix HNP2
IP2 address configuration
  |                     |             |                                |
Flow(IP1,IPcn) teminates
  |                     |             |                                |
  |<-new Flow(IP2,IPcn,...)-----------+------------------------------->|
  |                     |             |                                |

   Figure 5.  A flow uses the IP allocated from the network at which the
   MN is attached when the flow is initiated.

   To provide IP mobility support with distributed anchoring, the
   distributed anchors may need to message with each other.  When such
   messaging is needed, the anchors may need to discover each other as
   described in the FM behaviors and information elements (FM:2) in
   Section 3.2.2.

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   Then the anchors need to properly forward the packets of the flows as
   described in the FM behaviors and information elements (FM:1) in
   Section 3.2.2.

   If there are in-flight packets toward the old anchor while the MN is
   moving to the new anchor, it may be necessary to buffer these packets
   and then forward to the new anchor after the old anchor knows that
   the new anchor is ready.  Such are described in the FM behaviors and
   information elements (FM:4) in Section 3.2.2.

4.2.  IP prefix/address anchor switching to the new network

   The IP prefix/address anchoring may move without changing the IP
   prefix/address of the flow.  Here the LM and FM functions in Figures
   1(a) and 1(b) in Section 3.1 are implemented as shown in Figure 6.

Net1                                                   Net2

+---------------+                                      +---------------+
|AR1            |                                      |AR2            |
+---------------+                                      +---------------+
|CPA:           |                                      |CPA:           |
|LM:IP1<-->IPa2 |                                      |LM:IP1<-->IPa2 |
|---------------|                                      |---------------|
|DPA(IPa1):     |                                      |DPA(IPa2):     |
|anchors IP1    |                 move                 |anchors IP2,IP1|
|FM:DHCPv6-PD   |               =======>               |FM:DHCPv6-PD   |
+---------------+                                      +---------------+

+...............+                                      +---------------+
.MN(IP1)        .                 move                 |MN(IP2,IP1)    |
.flow(IP1,...)  .               =======>               |flow(IP1,...)  |
+...............+                                      +---------------+

   Figure 6.  IP prefix/address anchor switching to the new network.  MN
   with flow using IP1 in Net1 continues to run the flow using IP1 as it
   moves to Net2.

   As an MN with an ongoing session moves to a new network, the flow may
   preserve session continuity by moving the anchoring of the original
   IP prefix/address of the flow to the new network.  An example is in
   the use of BGP UPDATE messages to change the forwarding table entries
   as described in [I-D.mccann-dmm-flatarch] and also for 3GPP Evolved
   Packet Core (EPC) network in [I-D.matsushima-stateless-uplane-vepc].
   However, the response time and scalability of using a distributed
   routing protocol to update forwarding tables may be controversial.

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   Use of a centralized routing protocol with a centralized control
   plane as described in Section 4.2.1 will be more scalable.

   The location management provides information about which IP prefix
   from an AR in the original network is being used by a flow in which
   AR in a new network.  Such information needs to be deleted or updated
   when such flows have closed so that the IP prefix is no longer used
   in a different network.  The LM behaviors are described in
   Section 3.2.1.

   The FM functions are implemented through the DHCPv6-PD protocol.
   Here the anchor behavior to properly forward the packets for a flow
   as described in the FM behaviors and information elements FM:1 in
   Section 3.2.2 is realized by changing the anchor with DHCPv6-PD and
   also by reverting such changes later after the application has
   already closed and when the DHCPv6-PD timer expires.  If there are
   in-flight packets toward the old anchor while the MN is moving to the
   new anchor, it may be necessary to buffer these packets and then
   forward to the new anchor after the old anchor knows that the new
   anchor is ready.  Such are described in the FM behaviors and
   information elements FM:4 in Section 3.2.2.  The anchors may also
   need to discover each other as described in the FM behaviors and
   information elements FM:2.

   The security management function in the anchor node at a new network
   must allow to assign the original IP prefix/address used by the
   mobile node at the previous (original) network.  As the assigned
   original IP prefix/address is to be used in the new network, the
   security management function in the anchor node must allow to
   advertise the prefix of the original IP address and also allow the
   mobile node to send and receive data packets with the original IP
   address.

   The security management function in the mobile node must allow to
   configure the original IP prefix/address used at the previous
   (original) network when the original IP prefix/address is assigned by
   the anchor node in the new network.  The security management function
   in the mobile node also allows to use the original IP address for the
   previous flow in the new network.

4.2.1.  Centralized control plane

   An example of IP prefix anchor switching is in the case where Net1
   and Net2 both belong to the same operator network with separation of
   control and data planes ([I-D.liu-dmm-deployment-scenario] and
   [I-D.matsushima-stateless-uplane-vepc]), where the controller may
   send to the switches/routers the updated information of the
   forwarding tables with the IP address anchoring of the original IP

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   prefix/address at AR1 moved to AR2 in the new network.  That is, the
   IP address anchoring in the original network which was advertising
   the prefix will need to move to the new network.  As the anchoring in
   the new network advertises the prefix of the original IP address in
   the new network, the forwarding tables will be updated so that
   packets of the flow will be forwarded according to the updated
   forwarding tables.  The configuration in Figures 1(a) and 1(b) in
   Section 3.1 for which FM-CP and LM are centralized and FM-DP's are
   distributed.  applies here.  Figure 7 shows its implementation where
   LM is a binding between the original IP prefix/address of the flow
   and the IP address of the new DPA, whereas FM uses the DHCPv6-PD
   protocol.

Net1                                                   Net2
+----------------------------------------------------------------------+
|                            CPA:                                      |
|                            LM:IP1<-->IPa2                            |
|                            FM-CP                                     |
+----------------------------------------------------------------------+

+---------------+                                      +---------------+
|AR1            |                                      |AR2            |
+---------------+                                      +---------------+
|DPA(IPa1):     |                                      |DPA(IPa2):     |
|anchors IP1    |                 move                 |anchors IP2,IP1|
|FM:DHCPv6-PD   |               =======>               |FM:DHCPv6-PD   |
+---------------+                                      +---------------+

+...............+                                      +---------------+
.MN(IP1)        .                 move                 |MN(IP2,IP1)    |
.flow(IP1,...)  .               =======>               |flow(IP1,...)  |
+...............+                                      +---------------+

   Figure 7.  IP prefix/address anchor switching to the new network with
   with LM and FM-CP in a centralized control plane whereas the FM-DP's
   are distributed.

   The call flow in Figure 8 shows that MN is allocated HNP1 when it
   attaches to the p-AR.  A flow running in MN may or may not need IP
   mobility.  If it does, it may continue to use the previous IP prefix.
   If it does not, it may use a new IP prefix allocated from the new
   network.

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 MN                    p-AR          n-AR              DHCP Servers   CN
  |MN attaches to p-AR: |             |                     |          |
  |acquire MN-ID and profile          |                     |          |
  |--RS---------------->|             |                     |          |
  |<----------RA(HNP1)--|             |                     |          |
  |                     |             |             Allocate MN-HNP1   |
IP addr config          |             |                     |          |
  |                     |             |                     |          |
  |<-Flow(IP1,IPcn,...)-+--------------------------------------------->|
  |                     |             |                     |          |
  |MN detach from p-AR  |             |                     |          |
  |MN attach to n-AR    |             |                     |          |
  |                     |             |                     |          |
  |--RS------------------------------>|                     |          |
  |                     |             |                     |          |
  |                     |------DHCPv6 release-------------->|          |
  |                     |             |                     |          |
  |                     |             |--DHCPv6 PD request->|          |
  |                     |             |<-DHCPv6 PD reply--->|          |
  |                     |             |                     |          |
  |                 forwarding table updates                |          |
  |                     |             |                     |          |
  |<--------------RA(HNP2,HNP1)-------|                     |          |
  |                     |             |             Allocate MN-HNP2   |
IP addr config          |             |                     |          |
  |                     |             |                     |          |
  |<-Flow(IP1,IPcn,...)---------------+------------------------------->|
  |                     |             |                     |          |
  |  Flow(IP1,IPcn,...) terminates    |                     |          |
  |                     |             |                     |          |
  |                     | DHCPv6-PD timeout                 |          |
  |                     |             |                     |          |
  |                 forwarding table updates                |          |
  |                     |             |                     |          |
  |                     |             |                     |          |
  |<-new Flow(IP2,IPcn,...)-----------+------------------------------->|
  |                     |             |                     |          |

   Figure 8.  DMM solution.  MN with flow using IP1 in Net1 continues to
   run the flow using IP1 as it moves to Net2.

   As the MN moves from p-AR to n-AR, the p-AR as a DHCP client may send
   a DHCP release message to release the HNP1.  It is now necessary for
   n-AR to learn the IP prefix of the MN from the previous network so
   that it will be possible for Net2 to allocate both the previous
   network prefix and the new network prefix.  The network may learn the
   previous prefix in different methods.  For example, the MN may

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   provide its previous network prefix information by including it to
   the RS message [I-D.jhlee-dmm-dnpp].

   Knowing that MN is using HNP1, the n-AR sends to a DHCP server a
   DHCPv6-PD request to move the HNP1 to n-AR.  The server sends to n-AR
   a DHCPv6-PD reply to move the HNP1.  Then BGP route updates will take
   place here.

   In addition, the MN also needs a new HNP in the new network.  The
   n-AR may now send RA to n-AR, with prefix information that includes
   HNP1 and HNP2.  The MN may then continue to use IP1.  In addition,
   the MN is allocated the prefix HNP2 with which it may configure its
   IP addresses.  Now for flows using IP1, packets destined to IP1 will
   be forwarded to the MN via n-AR.

   As such flows have terminated and DHCP-PD has timed out, HNP1 goes
   back to Net1.  MN will then be left with HNP2 only, which it will use
   when it now starts a new flow.

   The anchor behavior to properly forward the packets for a flow as
   described in the FM behaviors and information elements (FM:1) in
   Section 3.2.2 is realized by changing the anchor with DHCPv6-PD and
   undoing such changes later when its timer expires and the application
   has already closed.  With the anchors being separated in control and
   data planes with LMs and FM-CP centralized in the same control plane,
   messaging between anchors and the discovery of anchors become
   internal to the control plane.  However, the centralized FM-CP needs
   to communicate with the distributed FM-DP as described as described
   in the FM behaviors and information elements (FM:3).  Such may be
   realized by the appropriate messages in [I-D.ietf-dmm-fpc-cpdp].
   Again, if there are in-flight packets toward the old anchor while the
   MN is moving to the new anchor, it may be necessary to buffer these
   packets and then forward to the new anchor after the old anchor knows
   that the new anchor is ready.  The corresponding FM behaviors and
   information elements (FM:4) are however realized by the internal
   behavior in the control plane together with signaling between the
   control plane and distributed data plane.

4.2.2.  Hierarchical network

   The configuration for a hierarchical network is shown in Figures 1(c)
   and 1(d) in Section 3.1.  With centralized control and with a
   centralized anchor, LM, CPA, CPN are co-located at the centralized
   control, and there is an AR with the DPA function supporting multiple
   forwarding switches (FW's) each with a DPN function.  A mobility
   event in this configuration involving change of FW but not of AR is
   shown in Figure 9.

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   Here the IP prefix allocated to the MN is anchored at the access
   router (AR) supporting the old FW to which the MN was originally
   attached as well as the new FW to which the MN has moved.

   The realization of LM may bet the binding between the IP prefix/
   address of the flow used by the MN and the IP address of the DPN to
   which MN has moved.  The implementation of FM to enable change of FW
   without changing AR may be accomplished using tunneling between the
   AR and the FW as described in [I-D.korhonen-dmm-local-prefix] and in
   [I-D.templin-aerolink] or using some other L2 mobility mechanism.

Net1                                                   Net2
+----------------------------------------------------------------------+
|                            CPA,CPN:                                  |
|                            LM:IP1<-->IPn2                            |
|                            FM-CP                                     |
+----------------------------------------------------------------------+

                           +---------------+
                           |AR1            |
                           +---------------+
                           |DPA(IPa1):     |
                           |anchors IP1    |
                           |FM:DHCPv6-PD   |
                           +---------------+

+---------------+                                      +---------------+
|FW1            |                                      |FW2            |
+---------------+                 move                 +---------------+
|DPN(IPn1):     |               =======>               |DPN(IPn2):     |
+---------------+                                      +---------------+

+...............+                                      +---------------+
.MN(IP1)        .                 move                 |MN(IP2)        |
.flow(IP1,...)  .               =======>               |flow(IP1,...)  |
+...............+                                      +---------------+

   Figure 9.  Mobility without involving change of IP anchoring in a
   network with hierarchy in which the IP prefix allocated to the MN is
   anchored at an Edge Router supporting multiple access routers to
   which the MN may connect.

   Here, the LM behaviors and information elements described in
   Section 3.2.1 provides information of which IP prefix from its FW
   needs to be used by a flow using which new FW.  The anchor behaviors

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   to properly forward the packets of a flow described in the FM
   behaviors and information elements (FM:1) may be realized with PMIPv6
   protocol ([I-D.korhonen-dmm-local-prefix]) or with AERO protocol
   ([I-D.templin-aerolink]) to tunnel between the AR and the FW.

4.2.3.  Hierarchical network with anchoring change

   The configuration for a hierarchical network is still shown in
   Figures 1(c) and 1(d) in Section 3.1.  Again, with centralized
   control and with a centralized anchor, LM, CPA, CPN are co-located at
   the centralized control, and there is an AR with the DPA function
   supporting multiple forwarding switches (FW's) each with a DPN
   function.  However, the mobility event involving change of FW may
   also involve a change of AR.  Such configuration is shown in
   Figure 10.

   This deployment case involves both a change of anchor from AR1 to AR2
   and a network hierarchy AR-FW.  It can be realized by a combination
   of changing the IP prefix/address anchoring from AR1 to AR2 with the
   mechanism as described in Section 4.2.1 and then forwarding the
   packets with network hierarchy AR-FW as described in Section 4.2.2.

   To change AR, AR1 acting as a DHCP-PD client may exchange message
   with the DHCP server to release the prefix IP1.  Meanwhile, AR2
   acting as a DHCP-PD client may exchange message with the DHCP server
   to delegate the prefix IP1 to AR2.

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Net1                                                   Net2
+----------------------------------------------------------------------+
|                            CPA,CPN:                                  |
|                            LM:IP1<-->IPa2,IPn2                       |
|                            FM-CP                                     |
+----------------------------------------------------------------------+

                            +---------------+
                            |Aggregate Point|
                            |---------------|
                            |FM,    LM      |
                            +---------------+

+---------------+                                      +---------------+
|AR1            |                                      |AR2            |
+---------------+                                      +---------------+
|DPA(IPa1):     |                                      |DPA(IPa2):     |
|anchors IP1    |                 move                 |anchors IP2,IP1|
|FM:DHCPv6-PD   |               =======>               |FM:DHCPv6-PD   |
+---------------+                                      +---------------+

+---------------+                                      +---------------+
|FW1            |                                      |FW2            |
+---------------+                 move                 +---------------+
|DPN(IPn1):     |               =======>               |DPN(IPn2):     |
+---------------+                                      +---------------+

+...............+                                      +---------------+
.MN(IP1)        .                 move                 |MN(IP2,IP1)    |
.flow(IP1,...)  .               =======>               |flow(IP1,...)  |
+...............+                                      +---------------+

   Figure 10.  Mobility involving change of IP anchoring in a network
   with hierarchy in which the IP prefix allocated to the MN is anchored
   at an Edge Router supporting multiple access routers to which the MN
   may connect.

5.  Security Considerations

   TBD

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6.  IANA Considerations

   This document presents no IANA considerations.

7.  Contributors

   This document has benefited from other work on mobility solutions
   using BGP update, on mobility support in SDN network, on providing
   mobility support only when needed, and on mobility support in
   enterprise network.  These work have been referenced.  While some of
   these authors have taken the work to jointly write this document,
   others have contributed at least indirectly by writing these drafts.
   The latter include Philippe Bertin, Dapeng Liu, Satoru Matushima,
   Peter McCann, Pierrick Seite, Jouni Korhonen, and Sri Gundavelli.

   Valuable comments have also been received from John Kaippallimil,
   ChunShan Xiong, and Dapeng Liu.

8.  References

8.1.  Normative References

   [I-D.dmm-ondemand-mobility-api]
              Yegin, A., Kweon, K., Lee, J., Park, J., and D. Moses, "On
              Demand Mobility API", draft-dmm-ondemand-mobility-api-00
              (work in progress), May 2015.

   [I-D.ietf-dmm-fpc-cpdp]
              Liebsch, M., Matsushima, S., Gundavelli, S., and D. Moses,
              "Protocol for Forwarding Policy Configuration (FPC) in
              DMM", draft-ietf-dmm-fpc-cpdp-01 (work in progress), July
              2015.

   [I-D.jhlee-dmm-dnpp]
              Lee, J. and Z. Yan, "Deprecated Network Prefix Provision",
              draft-jhlee-dmm-dnpp-00 (work in progress), October 2015.

   [I-D.korhonen-dmm-local-prefix]
              Korhonen, J., Savolainen, T., and S. Gundavelli, "Local
              Prefix Lifetime Management for Proxy Mobile IPv6", draft-
              korhonen-dmm-local-prefix-01 (work in progress), July
              2013.

   [I-D.liu-dmm-deployment-scenario]
              Liu, V., Liu, D., Chan, A., Lingli, D., and X. Wei,
              "Distributed mobility management deployment scenario and
              architecture", draft-liu-dmm-deployment-scenario-05 (work
              in progress), October 2015.

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   [I-D.matsushima-stateless-uplane-vepc]
              Matsushima, S. and R. Wakikawa, "Stateless user-plane
              architecture for virtualized EPC (vEPC)", draft-
              matsushima-stateless-uplane-vepc-05 (work in progress),
              September 2015.

   [I-D.mccann-dmm-flatarch]
              McCann, P., "Authentication and Mobility Management in a
              Flat Architecture", draft-mccann-dmm-flatarch-00 (work in
              progress), March 2012.

   [I-D.mccann-dmm-prefixcost]
              McCann, P. and J. Kaippallimalil, "Communicating Prefix
              Cost to Mobile Nodes", draft-mccann-dmm-prefixcost-02
              (work in progress), October 2015.

   [I-D.seite-dmm-dma]
              Seite, P., Bertin, P., and J. Lee, "Distributed Mobility
              Anchoring", draft-seite-dmm-dma-07 (work in progress),
              February 2014.

   [I-D.sijeon-dmm-deployment-models]
              Jeon, S. and Y. Kim, "Deployment Models for Distributed
              Mobility Management", draft-sijeon-dmm-deployment-
              models-01 (work in progress), October 2015.

   [I-D.templin-aerolink]
              Templin, F., "Asymmetric Extended Route Optimization
              (AERO)", draft-templin-aerolink-66 (work in progress),
              February 2016.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC5213]  Gundavelli, S., Ed., Leung, K., Devarapalli, V.,
              Chowdhury, K., and B. Patil, "Proxy Mobile IPv6",
              RFC 5213, DOI 10.17487/RFC5213, August 2008,
              <http://www.rfc-editor.org/info/rfc5213>.

   [RFC6275]  Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
              Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
              2011, <http://www.rfc-editor.org/info/rfc6275>.

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   [RFC7333]  Chan, H., Ed., Liu, D., Seite, P., Yokota, H., and J.
              Korhonen, "Requirements for Distributed Mobility
              Management", RFC 7333, DOI 10.17487/RFC7333, August 2014,
              <http://www.rfc-editor.org/info/rfc7333>.

   [RFC7429]  Liu, D., Ed., Zuniga, JC., Ed., Seite, P., Chan, H., and
              CJ. Bernardos, "Distributed Mobility Management: Current
              Practices and Gap Analysis", RFC 7429,
              DOI 10.17487/RFC7429, January 2015,
              <http://www.rfc-editor.org/info/rfc7429>.

8.2.  Informative References

   [Paper-Distributed.Mobility]
              Lee, J., Bonnin, J., Seite, P., and H. Chan, "Distributed
              IP Mobility Management from the Perspective of the IETF:
              Motivations, Requirements, Approaches, Comparison, and
              Challenges",  IEEE Wireless Communications, October 2013.

   [Paper-Distributed.Mobility.PMIP]
              Chan, H., "Proxy Mobile IP with Distributed Mobility
              Anchors",  Proceedings of GlobeCom Workshop on Seamless
              Wireless Mobility, December 2010.

   [Paper-Distributed.Mobility.Review]
              Chan, H., Yokota, H., Xie, J., Seite, P., and D. Liu,
              "Distributed and Dynamic Mobility Management in Mobile
              Internet: Current Approaches and Issues", February 2011.

Authors' Addresses

   H Anthony Chan
   Huawei Technologies
   5340 Legacy Dr. Building 3
   Plano, TX 75024
   USA

   Email: h.a.chan@ieee.org

   Xinpeng Wei
   Huawei Technologies
   Xin-Xi Rd. No. 3, Haidian District
   Beijing, 100095
   P. R. China

   Email: weixinpeng@huawei.com

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   Jong-Hyouk Lee
   Sangmyung University
   708 Hannuri Building
   Cheonan 330-720
   Korea

   Email: jonghyouk@smu.ac.kr

   Seil Jeon
   Instituto de Telecomunicacoes
   Campus Universitario de Santiago
   Aveiro 3810-193
   Portugal

   Email: seiljeon@av.it.pt

   Fred L. Templin
   Boeing Research and Technology
   P.O. Box 3707
   Seattle, WA  98124
   USA

   Email: fltemplin@acm.org

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