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

Versions: 00 01 02 03

NEMO Working Group                                                 C. Ng
Internet-Draft                                  Panasonic Singapore Labs
Expires: November 24, 2003                                    J. Charbon
                                       Keio and Louis Pasteur University
                                                            May 26, 2003


            Multi-Homing Issues in Bi-directional Tunneling
                  draft-ng-nemo-multihoming-issues-01

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

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

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

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

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

   This Internet-Draft will expire on November 24, 2003.

Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.

Abstract

   This document describes deployment scenario of multi-homed Network in
   Motion (NEMO) and attempts to identify issues that arises when
   supporting multi-homing in NEMO. It is also the objective of this
   document to build a full taxonomy covering multi-homed scenarios in
   NEMO, so as to facilitate explorations into this aspect of NEMO.









Ng & Charbon           Expires November 24, 2003                [Page 1]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


Table of Contents

   1.    Motivations  . . . . . . . . . . . . . . . . . . . . . . . .  3

   2.    Taxonomy . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.1   Explanations of Terms and Illustrations  . . . . . . . . . .  5
   2.1.1 Abbreviations  . . . . . . . . . . . . . . . . . . . . . . .  5
   2.1.2 Illustrations  . . . . . . . . . . . . . . . . . . . . . . .  5
   2.2   Classifications of Multi-homed Mobile Network. . . . . . . .  7
   2.2.1 (0,0,0): Single MR, Single HA, Single Prefix . . . . . . . .  8
   2.2.2 (0,0,1): Single MR, Single HA, Multiple Prefixes . . . . . .  9
   2.2.3 (0,1,0): Single MR, Multiple HAs, Single Prefix  . . . . . .  9
   2.2.4 (0,1,1): Single MR, Multiple HAs, Multiple Prefixes  . . . . 10
   2.2.5 (1,0,0): Multiple MRs, Single HA, Single Prefix  . . . . . . 10
   2.2.6 (1,0,1): Multiple MRs, Single HA, Multiple Prefixes  . . . . 11
   2.2.7 (1,1,0): Multiple MRs, Multiple HAs, Single Prefix . . . . . 11
   2.2.8 (1,1,1): Multiple MRs, Multiple HAs, Multiple Prefixes . . . 12
   2.3   Alternative Classifications  . . . . . . . . . . . . . . . . 13

   3.    Deployment Scenarios . . . . . . . . . . . . . . . . . . . . 15

   4.    Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . 17

   5.    Security Considerations  . . . . . . . . . . . . . . . . . . 21

   6.    Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22

         References . . . . . . . . . . . . . . . . . . . . . . . . . 23

         Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 24

         Intellectual Property and Copyright Statements . . . . . . . 25



















Ng & Charbon           Expires November 24, 2003                [Page 2]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


1. Motivations

   The problem of Network Mobility Support (NEMO) is identified in
   various previous works [1].  In essence, the problem of network in
   motion is to provide continuous Internet connectivity to nodes in a
   network that moves as a whole.  Nodes within the network that moves
   may not be aware of the network changing its point of attachment to
   the Internet.  This differs from the traditional problem of mobility
   support as addressed by Mobile IPv4 [3] and Mobile IPv6 [4].

   In Mobile IP, each mobile node has a permanent home domain.  When the
   mobile node is attached to its home network, it is assigned a
   permanent global address known as a home-address (HoA).  When the
   mobile node is away, i.e. attached to some other foreign networks, it
   is usually assigned a temporary global address known as a
   care-of-address (CoA).  The idea of mobility support is such that the
   mobile node can be reached at the home-address even when it is
   attached to other foreign networks.  This is done in [3][4] with the
   introduction of an entity at the home network known as a home agent
   (HA). Mobile nodes register their care-of-addresses with the home
   agents using messages known as Binding Updates.  The home agent is
   responsible to intercept messages that are addressed to the mobile
   node's home-address, and forward the packet to the mobile node's
   care-of-address using IP-in-IP Tunneling [5].

   Extending the concept of mobility support for individual hosts to
   mobility support for a network of nodes, the objective of a network
   in motion solution is to provide a mechanism where nodes in a mobile
   network can be reached by their permanent addresses, no matter where
   on the Internet the mobile network is attached to. There exist a few
   prior attempts to provide network mobility support, most of them
   based on using bi-directional tunnels between the mobile routers and
   the home agents of the mobile routers [6][7][8][9].

   In bi-directional tunnels between mobile routers and home agents, the
   mobile router controlling a mobile network performs routing of
   packets to and from the mobile network when it is in its home domain.
   When the mobile router and its mobile network move to a foreign
   domain, the mobile router registers its care-of-address with its home
   agent. An IP-in-IP tunnel is then set up between the mobile router
   and the home agent. Every packet going to the mobile network will be
   intercepted by the home agent and forwarded to the mobile router
   through the IP-in-IP tunnel.  The mobile router then forwards the
   packet to a host in its mobile network.  When a node in its mobile
   network wishes to send a packet out of the network, the mobile router
   intercepts the packet and forward the packet to the home agent
   through the IP-in-IP tunnel. The home agent then sends the packet out
   to the intended recipient.



Ng & Charbon           Expires November 24, 2003                [Page 3]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


   It is the interest of this memo to investigate if such a
   bi-directional tunneling approach can be extended to a mobile network
   that is multi-homed. More specifically, we wish to identify issues
   that may arise in bi-directional tunneling between mobile router and
   home agent when the mobile network is multi-homed.  To this end, this
   memo first builds up a taxonomy on multi-homed mobile network.
   Next, different deployment scenario are described for different
   configurations of the multi-homed mobile network.











































Ng & Charbon           Expires November 24, 2003                [Page 4]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


2. Taxonomy

2.1 Explanations of Terms and Illustrations

   This section describe items and abbreviations used in the
   illustrations of this Internet Draft.

2.1.1 Abbreviations

   Referring to the terminology of Network Mobility [2], the following
   abbreviations are used in figures illustrated throughout this draft:

      MR: Mobile Router

      HA: Mobile Network Home Agent

      AR: Access Router

      MNN: Mobile Network Node


2.1.2 Illustrations

   In all figures illustrated in this draft, the following convention
   will be used.

       _
     -|_|-

       R

   R is a router.


        p
     | <-_
     |--|_|-
     |
    L    R


   R advertised the Network Prefix p in the network link L.









Ng & Charbon           Expires November 24, 2003                [Page 5]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


       p1,p2
     | <-_
     |--|_|-
     |
    L

         R


   R advertised the Network Prefixes p1 and p2 in the network link L and
   p1 and p2 are different. [Todo: Different how ? 64 first bits
   different is enough or not ?]

       _  |
     -|_|=|
          |
       R

   R is a router with two or more global addresses on one interface, or
   with two or more interfaces on the same link, or two or more
   interfaces on different links.

   So the [=] symbol can be one of this cases:

    - Multi-Addressed MR.


                   AR2

                   p2
        _         <-_   _____
       |_|-|  _  |-|_|-|     |
        _  |-|_|-|  _  |     |
       |_|-|     |-|_|-|_____|
                  <-
                   p1

       MNNs  MR    AR1  Internet













Ng & Charbon           Expires November 24, 2003                [Page 6]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


    - Multi-Egress-Interfaced MR on the same link: [Todo: Add
   "Multi-Egress-Interfaced" term in the [Nemo-Term] ?]


        _        __|      _____
       |_|-|  _ /  |  _  |     |
        _  |-|_|   |-|_|-|     |
       |_|-|    \__|     |_____|
                   |
       MNNs   MR     AR  Internet


    - Multi-Egress-Interfaced MR on different links:


                     AR2
        _        __|  _   _____
       |_|-|  _ /  |-|_|-|     |
        _  |-|_|      _  |     |
       |_|-|    \__|-|_|-|_____|
                   |
       MNNs   MR     AR1 Internet



2.2 Classifications of Multi-homed Mobile Network.

   There are various configurations of a multi-homed mobile network,
   depending on how many mobile routers are present, how many egress
   interfaces and home addresses the mobile routers have, how many
   subnet prefixes are advertised to the mobile network nodes, etc. In
   order to facilitate discussions on multi-homed mobile network, it is
   necessary to identify what kind of configuration the mobile network
   is in.  Here, we identify three key parameters differentiating
   different multi-homed configurations.  With these parameters, we can
   refer to each configuration by the 3-tuple (w,x,y), where 'w', 'x',
   'y' are defined as follows:

   o  'w' differentiates the case of single mobile router (with multiple
      egress interfaces or multiple home addresses) versus the case of
      multiple mobile routers, where

      w=0 implies a mobile network has only a single mobile router. In
         this case, the mobile router either has multiple egress
         interfaces or multiple home addresses bound to a single egress
         interface.





Ng & Charbon           Expires November 24, 2003                [Page 7]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


      w=1 implies a mobile network has more than one mobile router
         advertising an egress route.

   o  'x' differentiates the case of a single home agent for the mobile
      network   versus the case of multiple home agents for the mobile
      network, where

      x=0 implies that a single home agent is assigned to manage binding
         updates of the mobile network.

      x=1 implies that more than one home agents (possibly in different
         administrative domains) manage the binding updates of the
         mobile network.

   o  'y' differentiates the case of single mobile network prefix versus
      multiple mobile network prefixes that is/are advertised to the
      mobile network node, where

      y=0 implies that a single subnet prefix is advertised to the
         mobile network nodes.

      y=1 implies that more than one subnet prefixes are advertised to
         the mobile network nodes.

   It can be seen that the above three parameters are fairly orthogonal
   to one another.  Thus different values of 'w', 'x' and 'y' give rise
   to different combinations of the 3-tuple (w,x,y).  A total of 8
   possible configurations can be identified.  These are described
   further in the following sub-sections.

2.2.1 (0,0,0): Single MR, Single HA, Single Prefix

   The (0,0,0) mobile network has only one mobile router advertising a
   single subnet prefix.  In addition, the mobile router associates with
   only one home agent at any one time.  This makes the mobile network
   very similar to a non-multi-homed mobile network, except for the fact
   that the mobile router may either (i) use more than one egress links
   at the same time, or (ii) use more than one home address at the same
   time.

   Since only one subnet prefix is advertised, the mobile network nodes
   are (usually) not multi-homed.









Ng & Charbon           Expires November 24, 2003                [Page 8]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


                        _____
        _    p      _  |     |
       |_|-|<-_  |-|_|-|     |-|        _
        _  |-|_|=|     |_____| |  _  |-|_|
       |_|-|     |             |-|_|-|
                                     |

       MNNs   MR   AR  Internet  AR    HA



2.2.2 (0,0,1): Single MR, Single HA, Multiple Prefixes

   The (0,0,1) mobile network has only one mobile router, which
   associates to only one home agent at any one time.  However, two or
   more subnet prefixes are advertised to the mobile network nodes.  No
   associations is assumed between the subnet prefixes and the home
   addresses of the mobile router.

   Since a plurality of subnet prefixes are advertised, mobile network
   nodes can generally be multi-homed themselves, where each mobile
   network node is allocated one address in each subnet prefix.


                        _____
        _   p1,p2   _  |     |
       |_|-|<-_  |-|_|-|     |-|        _
        _  |-|_|=|     |_____| |  _  |-|_|
       |_|-|     |             |-|_|-|
                                     |

       MNNs   MR    AR Internet  AR    HA



2.2.3 (0,1,0): Single MR, Multiple HAs, Single Prefix

   The (0,1,0) mobile network has only one mobile router advertising a
   single subnet prefix.  The mobile router, however, associates to
   multiple home agents, possibly one home agent per home addresses. No
   assumption is made on whether or not the home agents belongs to the
   same administrative domain.

   Since only one subnet prefix is advertised, the mobile network nodes
   are (usually) not multi-homed.






Ng & Charbon           Expires November 24, 2003                [Page 9]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


                                 AR    HA2
                                  _  |
                               |-|_|-|  _
                        _____  |     |-|_|
        _    p      _  |     |-|
       |_|-|<-_  |-|_|-|     |
        _  |-|_|=|     |_____|-|        _
       |_|-|     |             |  _  |-|_|
                               |-|_|-|
                                     |
       MNNs  MR    AR  Internet  AR    HA1



2.2.4 (0,1,1): Single MR, Multiple HAs, Multiple Prefixes

   The (0,1,1) mobile network has only one mobile router.  However, the
   mobile router advertises more than one subnet prefix, and also
   associates to multiple home agents at the same time, possibly one
   home agent per home address.  No assumptions is made on whether or
   not the home agents belongs to the same administrative domain.

   Since a plurality of subnet prefixes are advertised, mobile network
   nodes can generally be multi-homed themselves, where each mobile
   network node is allocated one address in each subnet prefix.


                                 AR    HA2
                                  _  |
                               |-|_|-|  _
                        _____  |     |-|_|
        _   p1,p2   _  |     |-|
       |_|-|<-_  |-|_|-|     |
        _  |-|_|=|     |_____|-|        _
       |_|-|     |             |  _  |-|_|
                               |-|_|-|
                                     |
       MNNs  MR    AR  Internet  AR    HA1



2.2.5 (1,0,0): Multiple MRs, Single HA, Single Prefix

   The (1,0,0) mobile network has more than one mobile router
   advertising global routes.  These mobile routers, however, advertise
   the same subnet prefix and associate to the same home agent.  Since
   only one subnet prefix is advertised, the mobile network nodes are
   (usually) not multi-homed.



Ng & Charbon           Expires November 24, 2003               [Page 10]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


             MR2

             p
            <-_  |
        _  |-|_|-|  _____
       |_|-|     |-|     |
        _  |       |     |-|        _
       |_|-|  _  |-|_____| |  _  |-|_|
           |-|_|-|         |-|_|-|
            <-   |               |
             p

       MNNs  MR1   Internet  AR    HA



2.2.6 (1,0,1): Multiple MRs, Single HA, Multiple Prefixes

   The (1,0,1) mobile network has more than one mobile router
   advertising different global routes and different subnet prefixes.
   However, these mobile routers associate to the same home agents.

   Since a plurality of subnet prefixes are advertised, mobile network
   nodes can generally be multi-homed themselves, where each mobile
   network node is allocated one address in each subnet prefix.


             MR2

             p2
            <-_  |
        _  |-|_|-|  _____
       |_|-|     |-|     |
        _  |       |     |-|        _
       |_|-|  _  |-|_____| |  _  |-|_|
           |-|_|-|         |-|_|-|
            <-   |               |
             p1

       MNNs  MR1   Internet  AR    HA



2.2.7 (1,1,0): Multiple MRs, Multiple HAs, Single Prefix

   The (1,1,0) mobile network has more than one mobile router
   advertising different global routes.  The mobile routers are also
   associated to more than one home agents at any one time. No



Ng & Charbon           Expires November 24, 2003               [Page 11]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


   assumptions is made on whether or not the home agents belongs to the
   same administrative domain.  However, the mobile routers advertises
   the same subnet prefix.  Since only one subnet prefix is advertised,
   the mobile network nodes are (usually) not multi-homed.


             MR2             AR    HA2

             p                _  |
            <-_  |         |-|_|-|  _
        _  |-|_|-|  _____  |     |-|_|
       |_|-|     |-|     |-|
        _  |       |     |
       |_|-|  _  |-|_____|-|        _
           |-|_|-|         |  _  |-|_|
            <-   |         |-|_|-|
             p                   |

       MNNs  MR1   Internet  AR    HA1



2.2.8 (1,1,1): Multiple MRs, Multiple HAs, Multiple Prefixes

   The (1,1,1) mobile network has more than one mobile router
   advertising different global routes and different subnet prefixes.
   The mobile routers are also associated to more than one home agent at
   any one time.  No assumptions is made on whether or not the home
   agents belongs to the same administrative domain.

   Since a plurality of subnet prefixes are advertised, mobile network
   nodes can generally be multi-homed themselves, where each mobile
   network node is allocated one address in each subnet prefix.


             MR2             AR    HA2

             p2               _  |
            <-_  |         |-|_|-|  _
        _  |-|_|-|  _____  |     |-|_|
       |_|-|     |-|     |-|
        _  |       |     |
       |_|-|  _  |-|_____|-|        _
           |-|_|-|         |  _  |-|_|
            <-   |         |-|_|-|
             p1                  |

       MNNs  MR1   Internet  AR    HA1



Ng & Charbon           Expires November 24, 2003               [Page 12]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


2.3 Alternative Classifications

   In the mailing list, Pascal Thubert (Cisco System) proposed an
   alternative classification.  He has a set of 4 categories, based on
   two orthogonal parameters: the number of home agents, and the number
   of subnet prefixes advertised.  Since the two parameters are
   orthogonal, the categories are not mutually exclusive.  The four
   categories are:

   o  Tarzan: Single HA for Different Care-ofs of Same Prefix

      This is the case where one mobile router registers different
      care-of-addresses to the same home agent for the same subnet
      prefix.  This is equivalent to the case of x=0, i.e. the (0,0,*)
      mobile network.

   o  JetSet: Multiple HA for Different Care-ofs of Same Prefix

      This is the case where the mobile router registers different
      care-of-addresses to different home agents for the same subnet
      prefix.  This is equivalent to the case of x=1, i.e. the (0,1,*)
      mobile network.

   o  Shinkansen: Single Prefix Advertised by Mobile Router(s)

      This is the case where one subnet prefix is announced by different
      mobile routers.  This is equivalent to the case of y=0, i.e. the
      (1,*,0) mobile network.

   o  DoubleBed: Multiple Prefixes Advertised by Mobile Router(s)

      This is the case where more than one subnet prefixes are announced
      by the different mobile routers.  This is equivalent to the case
      of y=0, i.e. the (1,*,1) mobile network.

   Thubert's classifications is problem-oriented, as oppose to the 8
   classifications in this draft, which are configurations oriented. We
   see also that one can draw association between some of the 8
   classifications in this draft with the each of the 4 categories put
   forward by Thubert. Hence, in a rough manner, one can say the 4
   classes drawn by Thubert is actually a subset of the 8 configurations
   defined, though such an associations is a vague one since both
   partitioned the multi-homed mobile network differently
   (problem-oriented versus configuration-oriented).

   It is, however, the authors' belief that by analyzing each
   configurations, problems and issues of multi-homed mobile network can
   be more thoroughly identified.  It may well be that after analysis,



Ng & Charbon           Expires November 24, 2003               [Page 13]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


   we come to the same 4 specific problems Thubert has identified.  Even
   so, the exercise of analysis each configuration should be helpful to
   the understanding of each problem.
















































Ng & Charbon           Expires November 24, 2003               [Page 14]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


3. Deployment Scenarios

   [ To be re-organized -- cwng ]

   One example of the (0,0,*) mobile network is that a single Internet
   Service Provider (ISP) offers two different wireless public access
   methods such as IEEE 802.11 and GPRS.  A mobile router with both
   access interfaces (i.e. 802.11 and GPRS capabilities) may subscribe
   to the same ISP and is allowed to use both access methods.  The ISP
   will choose to provide a single home agent for the same mobile router
   for ease of management.

   This configuration is useful for maintaining connectivity between
   several interfaces.  An example will be to use 802.11 in town and
   GPRS in the country side.  In addition, it can also provide some
   multi-homing benefits (such as Fault-Tolerance / Policy Sharing) to
   MNNs without having to involve the MNNs.

   Extending the above example to a (0,1,*) mobile network, the mobile
   router may subscribe to different ISPs for different access
   technologies. For instance, it may subscribe to 802.11 public access
   services using one ISP, and subscribe to GPRS services from another
   ISP.  In this case, the two different ISPs will provide two different
   home agents for the same mobile router.  Since the two ISPs are
   independent, under normal situation, each ISP will delegates
   different subnet prefixes to the mobile network, thus forming a
   (0,1,1) mobile network.

   An example of the (1,*,*) mobile network is when a mobile network
   contains more than one device with independent routes to the global
   Internet.  An excellent illustration is the Wireless Personal Area
   Network (W-PAN) where a mobile phone on the W-PAN connects to the
   Internet via GPRS services, and a Personal Digital Assistant (PDA) on
   the same W-PAN connects to the Internet via 802.11 public access. If
   the ISPs provide both access technologies, then the subscriber can
   subscribes to a all-in-one package where the ISP provides a single
   home agent to manage the mobile network, and delegates a single
   subnet prefix to the mobile network.  This forms a (1,0,0) mobile
   network. Alternatively, the subscriber can subscribes to two ISPs for
   each access mechanism, thus giving a (1,1,1) mobile network.

   The (1,*,0) configuration provides easily a router redundancy and/or
   HA redundancy for big mobile networks, such as within a train or a
   plane, or critical mobile networks, such as those deployed in
   ambulances, fire engines, or military vehicles.






Ng & Charbon           Expires November 24, 2003               [Page 15]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


   Deployment example for (0,1,0) [~JetSet]


                                [The Jet]

         _                      |\_______           _
       -|_|-  <-------------->  |____~___\  <-->  -|_|-

        HA1                     MN inside the      HA2
                                plane.
       Paris                                      New York


   In this example, the MR sends the same PBU to both HAs in different
   cities, and communicates with both simultaneously. Thus a
   Correspondent Node near Paris can choose the Paris's HA to send its
   packets, and the MR inside the plane should send its packet to the
   New York's HA (which is nearer).

   Example for a (*,*,1) mobile network is a car network, where there
   may be different logical subnets:

   o  the User Network which provides Internet connectivity to
      passengers;

   o  the Control Network which exchanges car information (e.g.
      position, movement, intern constants) with the others cars, or
      with the society who use this car; and

   o  the Safeguard Network which shares state information of the car
      with the emergency/repairing companies, or the emergency agencies
      in case of accidents.

   Because of these differences it can be useful to attribute a
   different network prefix for each network to clearly separate each
   entity and each network prefix should be send to a different subnet
   link.














Ng & Charbon           Expires November 24, 2003               [Page 16]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


4. Analysis

   [ This section is hastily set up for the benefit of the solution
   design team. This section will be re-organized in the next version --
   cwng ]

   This section, we attempt to analyze what are the problems faced in
   each of the 8 categories.  It shouldn't matter if some of the
   categories share the same problem(s).

   o  (0,0,0) Mobile Network

      The (0,0,0) mobile network has only one mobile router registering
      more than one care-of-addresses to the same home agent, and
      advertising only one prefix.  The mobile router can either have
      more than one care-of-addresses bound to the same home-address, or
      it can have various care-of-address and home-address pairs.

      Either way, this is a MIPv6 problem.  Multiple pairs of different
      care-of-address and home-address is perfectly alright with MIPv6.
      The fact that they specify the same subnet prefix in binding
      updates shouldn't cause a problem either.  Having a home-address
      tied to multiple care-of-address may be a problem for MIPv6. This
      will require a solution like [10].

   o  (0,0,1) Mobile Network

      The (0,0,1) mobile network is similar to the (0,0,0) mobile
      network, and thus face the same problem when there is only one
      home-address bound to multiple care-of-addresses.  However, the
      (0,0,1) has one NEMO-specific problem if more than one subnet
      prefixes are being taken care-of by a single home-address and
      care-of-address pair. This is assuming prefix-scoped binding
      update is used, which does not allow more than one prefix be
      specified in a single binding update.

   o  (0,1,0) Mobile Network

      The (0,1,0) mobile network has one mobile router registering to
      multiple home agents.  There is the question of whether a mobile
      router can register the same home-address to different home agents
      simultaneously with the 'H' bit set.  If not, the mobile router
      can only register different home-address and care-of-address pairs
      to different home agents.  In any case, this is a MIPv6 issue.

      The NEMO-specific problem is the fact that a subnet prefix has a
      care-of in different home agents.  It might be possible that only
      one home-agent will actively advertise a route to the subnet



Ng & Charbon           Expires November 24, 2003               [Page 17]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


      prefix.  The case of multiple home agents at different domains
      advertising a route to the same subnet prefix may pose a problem
      in the routing infrastructure as a whole.  The implications of
      this aspect needs further exploration.

   o  (0,1,1) Mobile Network

      The (0,1,1) mobile network has one mobile router registering to
      multiple home agents multiple subnet prefixes.  The same question
      of whether the same home-address can be simultaneously registered
      to multiple home agents.

      This (0,1,1) network can avoid the problem of registering care-ofs
      for the same prefix to different home agents by registering
      care-of for one prefix at one home-agent.

   o  (1,0,0) Mobile Network

      The (1,0,0) mobile network has two or more active egress mobile
      routers, registering to same home agents, and advertising the same
      prefix. May not have any problem at all if the mobile routers are
      manually configured to announce the same prefix.  It is also
      possible that prefix delegation is used to ensure all routers
      advertise the same subnet prefix since all routers are handled by
      the same home agent. The home-agent will see two HoA-CoA pairs
      taking care of the same subnet prefix.

   o  (1,0,1) Mobile Network

      The (1,0,1) mobile network has multiple active egress mobile
      routers registering to the same home-agent, and advertising
      multiple prefixes. If a mobile router is advertising more than one
      prefix, we have the same problem as (0,0,1) as in how to register
      more than one subnet prefix to the same home-agent.

      On the other hand, if each mobile router take cares of a separate
      (and only one) subnet prefix, then there should not be any
      NEMO-specific problem.

   o  (1,1,0) Mobile Network

      The (1,1,0) mobile network has multiple mobile routers registering
      to different home agents, but advertising the same prefix.  There
      is the same issues as in (0,1,0) of a subnet prefix having a
      care-of in different home agents.  In addition, there is a
      question how to perform prefix delegation such that two home
      agents will delegate the same prefix to different mobile routers.
      Certain level of home-agent co-ordination may be required here.



Ng & Charbon           Expires November 24, 2003               [Page 18]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


   o  (1,1,1) Mobile Network

      The (1,1,1) mobile network has multiple mobile routers,
      registering to multiple home-agents and advertising prefixes.
      This may be a case of multiple non-multi-homed network
      superimposed together, i.e. each mobile router take cares of one
      prefix, and register to separate home agents.

      On the other hand, if one mobile router takes cares of more than
      one prefix, we have similar problems as (0,0,1) and (1,0,1).  In
      addition, if more than one mobile router takes care of the same
      prefix, we have similar issues as (1,1,0).  In any case, we see
      that the problems within this configurations can be decomposed
      into problems from other configurations.

   From the above analysis, we can identify the following problems
   relating to multi-homed mobile network:

   o  Multiple care-of-addresses to one home-address:

      *  How to register two care-of-address binding to one
         home-address?

      *  In single or multiple binding message(s)?

      *  How to selectively update a care-of-address?

      *  MIPv6 specific?

      *  Wakikawa's draft [10] specifically addresses this issue.

   o  Multiple prefixes taken care of by a single home-address:

      *  How to register multiple prefix scope under the same
         home-address?

      *  In single or multiple binding message(s)?

      *  How to selectively update the care-of of a subnet prefix?

      *  Similar to the 'Tarzan' problem illustrated by Thubert.

   o  A single home-address registered to multiple home agents:

      *  Is this allowed?

      *  MIPv6-specific?




Ng & Charbon           Expires November 24, 2003               [Page 19]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


   o  A single subnet prefix registered to multiple home agents:

      *  Is this allowed?

      *  Is this allowed if the prefix is bound to the same
         home-address?

      *  Any routing issue?

      *  If prefix delegation is used, possibility of requiring home
         agents co-ordination.

      *  Similar to the 'JetSet' problem illustrated by Thubert.

   o  A single prefix advertised by multiple mobile routers from
      multiple home agents:

      *  If prefix delegation is used, possibility of requiring home
         agents co-ordination.

      *  Similar to the 'Shinkansen' problem illustrated by Thubert.

   o  [TBD: anymore]




























Ng & Charbon           Expires November 24, 2003               [Page 20]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


5. Security Considerations

   This document is an on-going work to classify the taxonomy in
   multi-homing of mobile networks.  There should be a separate draft
   produced by the working group to analyze security threats for network
   in motion.  As such, no special security considerations is listed
   here.  However, since this memo also looks into the analysis of
   problems in a multi-homed mobile network, we will add problems
   related to security threat here as and when they are encountered.  We
   also encourage interested readers to contribute to this part.









































Ng & Charbon           Expires November 24, 2003               [Page 21]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


6. Acknowledgements

   The authors would like to thank people who have given valuable
   comments on various multi-homing issues on the mailing list, and also
   those who have suggested directions in the 56th IETF Meeting.














































Ng & Charbon           Expires November 24, 2003               [Page 22]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


References

   [1]   Ernst, T., et al, "Network Mobility Support Goals and
         Requirements", Internet Draft:
         draft-ietf-nemo-requirements-01.txt, Work In Progress, May
         2003.

   [2]   Ernst, T. and H. Lach, "Network Mobility Support Terminology",
         Internet Draft: draft-ietf-nemo-terminology-00.txt, Work In
         Progress, May 2003.

   [3]   Perkins, C., "IP Mobility Support for IPv4", RFC 3344, August
         2002.

   [4]   Johnson, D. B., Perkins, C. E. and Arkko, J., "Mobility Support
         in IPv6", Internet Draft: draft-ietf-mobileip-ipv6-21.txt, Work
         In Progress, February 2003.

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

   [6]   Kniveton, T. J., et al, "Mobile Router Tunneling Protocol",
         Internet Draft: draft-kniveton-mobrtr-03.txt, Work In Progress,
         November 2002.

   [7]   Petrescu, A., et al, "Issues in Designing Mobile IPv6 Network
         Mobility with the MR-HA Bidirectional Tunnel (MRHA)", Internet
         Draft: draft-petrescu-nemo-mrha-00.txt, Work In Progress,
         October 2002.

   [8]   Ng, C. W. and Tanaka, T., "Securing Nested Tunnels Optimization
         with Access Router Option", Internet Draft:
         draft-ng-nemo-access-router-option-00.txt, Work In Progress,
         October 2002.

   [9]   Wakikawa, R., et al, "Basic Network Mobility Support", Internet
         Draft: draft-wakikawa-nemo-basic-00.txt, Work In Progress,
         February 2003.

   [10]  Wakikawa, R., et al, "Multiple Care-of-Address Registration on
         Mobile IPv6", Internet Draft:
         draft-wakikawa-mobileip-multiplecoa-00.txt, Work In Progress,
         February 2003.








Ng & Charbon           Expires November 24, 2003               [Page 23]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


Authors' Addresses

   Chan-Wah Ng
   Panasonic Singapore Laboratories Pte Ltd
   Blk 1022 Tai Seng Ave #06-3530
   Tai Seng Industrial Estate
   Singapore  534415
   SG

   Phone: +65 65505420
   EMail: cwng@psl.com.sg


   Julien Charbon
   Keio University, Louis Pasteur University
   Keio University.
   5322 Endo
   Fujisawa-shi, Kanagawa  252-8520
   JP

   Phone: +81-466-49-1100
   Fax:   +81-466-49-1395
   EMail: julien@sfc.wide.ad.jp
   URI:   http://www.sfc.wide.ad.jp/~julien/



























Ng & Charbon           Expires November 24, 2003               [Page 24]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights. Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11. Copies of
   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to
   obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification can
   be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard. Please address the information to the IETF Executive
   Director.


Full Copyright Statement

   Copyright (C) The Internet Society (2003). All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works. However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assignees.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION



Ng & Charbon           Expires November 24, 2003               [Page 25]


Internet-Draft        Multi-homing Issues in NEMO               May 2003


   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.











































Ng & Charbon           Expires November 24, 2003               [Page 26]


Html markup produced by rfcmarkup 1.129d, available from https://tools.ietf.org/tools/rfcmarkup/