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Network Mobility Working Group                                   C. W. Ng
Internet-Draft                                   Panasonic Singapore Labs
Expires: August 2003                                            T. Tanaka
                                          Panasonic Mobile Communications
                                                            February 2003

              Multi-Homing Issues in Bi-Directional Tunneling
                  draft-ng-nemo-multihoming-issues-00.txt

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026 [1].

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


Abstract

   This document describes deployment scenario of multi-homed NEMO and
   attempts to identify issues that arises when supporting multi-homing
   in NEMO.  This document also proposes an approach to facilitate
   multi-homing in NEMO.  However, it is not the objective of this memo
   to define a specification for multi-homing support in NEMO.


Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC-2119 [2].



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Table of Contents

   1. Introduction...................................................3
      1.1. Terms Used................................................5
      1.2. Organization..............................................5
   2. Multi-Homing in NEMO...........................................6
      2.1. Deployment Scenarios of Multi-homed NEMO..................6
         2.1.1. Single Mobile Router with Multiple Egress Interfaces
         Bound to a Single Home Agent................................6
         2.1.2. Single Mobile Router with Multiple Egress Interfaces
         Bound to Different Home Agents..............................7
         2.1.3. Multiple Mobile Routers..............................8
      2.2. Issues of Multi-Homing in NEMO............................9
   3. Using Multi-Homing Features in Bi-Directional Tunnels.........11
      3.1. Detecting Presence of Alternate Routes...................11
      3.2. Re-Establishment of Bi-Directional Tunnels...............12
         3.2.1. Using Alternate Egress Interface....................12
         3.2.2. Using Alternate Mobile Router.......................12
      3.3. To Avoid Tunneling Loop..................................13
      3.4. Other Considerations.....................................13
   4. Security Considerations.......................................14
   References.......................................................14
   Author's Addresses...............................................16























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1.  Introduction

   The problem of Network Mobility Support (NEMO) is identified in
   various previous works [3,4,5,6].  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 [7] in Internet Protocol version
   4 (IPv4) [8] and Mobile IPv6 [9] in Internet Protocol version 6
   (IPv6) [10].

   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 [7,9] 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 [11,12].

   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 [13,14,15,16,17].

   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


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   through the IP-in-IP tunnel.  The home agent then sends the packet
   out to the intended recipient.

   However, the simple approach of bi-directional tunnel does not cater
   well to other powerful features of IPv4 and IPv6, such as multi-
   homing.  A network in motion can be multi-homed if there exist a
   plurality of egress interfaces that offer independent routes to the
   global Internet.  If all of these interfaces belong to the same
   mobile router, then only the mobile router is multi-homed.  The
   mobile network nodes behind the mobile router see only one egress
   router, thus they are not multi-homed.  On the other hand, if these
   interfaces belong to separate routers, then the mobile network nodes
   will see different egress routers and can attach to more than one of
   these egress routers simultaneously.  These mobile network nodes are
   thus multi-homed themselves.

   Mobile networks typically have wireless connection to the global
   network.  Though wireless technology has improved tremendously over
   the recent years, it is still more prone to channel instability and
   noise when compared to wired networks.  One of the advantages of
   multi-homing is that mobile network nodes can use an alternative path
   to reach and be reached by the global Internet when one of its uplink
   is down.  This is extremely useful for wireless-based mobile nodes,
   as it provides a back up mechanism to the unstable wireless uplink.

   However, with bi-directional tunneling mechanism employed by mobile
   routers, nodes only chose one mobile router as their default router.
   When this mobile router loses its connection to the global Internet,
   it can no longer maintain a tunnel with its home agent.  Thus all
   nodes that made use of the mobile router will lose their connectivity
   to the global network as well, even though there may exits another
   mobile router on the same network that has an active link to the
   global Internet.

   Mobile network nodes may eventually realize that their default router
   no longer has a route to the global network, and select an alternate
   mobile router as their default router.  Such a scheme relies on the
   mobile network nodes to perform their own route discovery.  It adds
   processing load to mobile network nodes, which may have very limited
   processing powers (e.g. embedded devices), and incurs additional
   delays (for the mobile network nodes to realize their current default
   route is down). In addition, different mobile routers will advertise
   different subnet prefixes, and thus when mobile nodes eventually
   switch their default routers, they will have to use different care-
   of-addresses.  This requires sending of binding updates to their
   home-agents, further increasing the lag of recovery.




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1.1.  Terms Used

   It is assumed that readers are familiar with the NEMO terminology
   described in [18].  In addition, the following definitions of terms
   are used in this memo:

      Alternate Mobile Router

         This term is used when discussing the behaviour of a mobile
         router.  It refers to another mobile router that is connected
         to the same mobile network and has an independent route to the
         global Internet.

      Alternate Egress Interface

         This term is used when discussing the behaviour of a mobile
         router with multiple egress interfaces.  It refers to another
         egress interface that is connected to the global Internet.

      Failed Egress Interface

         This term refers to the egress interface of a mobile router
         that has lost its connection to the global Internet.


1.2.  Organization

   In the remaining portions of this memo, we will first describe the
   motivations and scenarios for deploying multi-homed mobile networks
   in Section 2.  The issues in using bi-directional tunneling in a
   multi-homed mobile network will also be described.  In Section 3, we
   explore into possible solutions to the problems listed in Section 2,
   and investigate methods of optimizing bi-directional tunneling to
   employ features of multi-homing.

















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2.  Multi-Homing in NEMO

2.1.  Deployment Scenarios of Multi-homed NEMO

2.1.1.  Single Mobile Router with Multiple Egress Interfaces Bound to a
        Single Home Agent

   First type of multi-homed mobile network contains only one mobile
   router.  This mobile router have a plurality of egress interfaces,
   all of which bounds to the same home agent.  In such cases, the
   mobile router usually only advertise a single network prefix to the
   mobile network.  This is illustrated in Figure 2.1 below.

                                          +-------------------------+
                                          |       |  Binding Cache  |
                                          |       |  HoA       CoA  |
                                          |       |  1::1      2::1 |
                                          | Home  |  1::2      3::1 |
                                          | Agent |=================|
                                          |       |  Routing Table  |
                                          |       | Dest   Next-Hop |
                                          |       | 1:1::/96   1::1 |
                                          +-------------------------+
                                              |
                                              |
                  +-------------------------------------+
                  |                                     |
                  |              Internet               |
                  |                                     |
                  +-------------------------------------+
                               |        |
                   Interface 1 |        | Interface 2
                      CoA=2::1 |        | CoA=3::1
                      HoA=1::1 |        | HoA=1::2
                               |        |
                          +--------------------+
                          |    Mobile Router   |
                          +--------------------+
                                    | prefix=1:1::/96
                    ----------------?----------------
                                    |
                           +----------------+
                           | Mobile Network | address=1:1::x
                           |      Node x    |
                           +----------------+

    Figure 2.1 - Single MR with Multiple Egress Interfaces to a Single
                                Home Agent.



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   One example of this type of deployment scenario 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.


2.1.2.  Single Mobile Router with Multiple Egress Interfaces Bound to
        Different Home Agents

   The second type of multi-homed mobile network involves a single
   mobile router with more than one egress interfaces.  Each of these
   egress interfaces is bound to different home agents.  This is
   illustrated in Figure 2.2 below.  The mobile router can advertise a
   single network prefix and inject the appropriate routing update to
   the home agents (not shown in the figure).  In this case, the mobile
   router uses only one interface for bi-directional tunneling.
   Alternatively, the mobile router could also advertise two different
   network prefixes (as shown in the figure).  Both egress interfaces
   are then utilized, and the mobile router maintains two active bi-
   directional tunnels with both home agents.

   Example of this kind of deployment scenarios is when a mobile router
   subscribes to different ISPs.  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.






















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     +-------------------------+          +-------------------------+
     |  Binding Cache  |       |          |       |  Binding Cache  |
     |  HoA       CoA  |       |          |       |  HoA       CoA  |
     |  1::1      3::1 |  Home |          | Home  |  2::1      4::1 |
     |=================| Agent |          | Agent |=================|
     |  Routing Table  |   1   |          |   2   |  Routing Table  |
     | Dest   Next-Hop |       |          |       | Dest   Next-Hop |
     | 1:1::/96   1::1 |       |          |       | 2:1::/96   2::1 |
     +-------------------------+          +-------------------------+
                           |                  |
                           |                  |
                  +-------------------------------------+
                  |                                     |
                  |              Internet               |
                  |                                     |
                  +-------------------------------------+
                               |        |
                   Interface 1 |        | Interface 2
                      CoA=3::1 |        | CoA=4::1
                      HoA=1::1 |        | HoA=2::1
                               |        |
                          +--------------------+
                          |    Mobile Router   |
                          +--------------------+
                                    | prefix=1:1::/96, 2:1::/96
                    ----------------?----------------
                                    |
                           +----------------+
                           | Mobile Network | address=1:1::x
                           |      Node x    |    or 2:1::x
                           +----------------+

    Figure 2.2 - Single MR with Multiple Egress Interfaces to Different
                               Home Agents.


2.1.3.  Multiple Mobile Routers

   The third type of multi-homed mobile network involves multiple mobile
   routers on the same mobile network.  Each of these mobile routers
   advertise an egress route to the global Internet.  In such cases, two
   different network prefixes are advertised to the mobile network
   nodes.  This is illustrated in Figure 2.3 below.

   Example of this kind of deployment scenarios 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


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   Internet via GPRS services, and a Personal Digital Assistant (PDA) on
   the same W-PAN connects to the Internet via 802.11 public access.

     +-------------------------+          +-------------------------+
     |  Binding Cache  |       |          |       |  Binding Cache  |
     |  HoA       CoA  |       |          |       |  HoA       CoA  |
     |  1::1      3::1 |  Home |          | Home  |  2::1      4::1 |
     |=================| Agent |          | Agent |=================|
     |  Routing Table  |   1   |          |   2   |  Routing Table  |
     | Dest   Next-Hop |       |          |       | Dest   Next-Hop |
     | 1:1::/96   1::1 |       |          |       | 2:1::/96   2::1 |
     +-------------------------+          +-------------------------+
                           |                  |
                           |                  |
                  +-------------------------------------+
                  |                                     |
                  |              Internet               |
                  |                                     |
                  +-------------------------------------+
                            |                |
                   CoA=3::1 |                | CoA=4::1
                   HoA=1::1 |                | HoA=2::1
                            |                |
                      +----------+      +----------+
                      |  Mobile  |      |  Mobile  |
                      | Router 1 |      | Router 2 |
                      +----------+      +----------+
           prefix=1:1::/96 |                 | prefix=2:1::/96
                    -------?--------?--------?-------
                                    |
                           +----------------+
                           | Mobile Network | address=1:1::x
                           |      Node x    |    or 2:1::x
                           +----------------+

           Figure 2.3 - Multiple MRs on the Same Mobile Network.


2.2.  Issues of Multi-Homing in NEMO

   When a mobile network is multi-homed, mobile network nodes can choose
   to use different routes to send packets to the global Internet,
   either by way of using different global addresses, or by forwarding
   the packets to different routers.

   However, with bi-directional tunneling mechanism employed by mobile
   routers, mobile network nodes only chose one mobile router as their
   default router.  When this mobile router loses its connection to the
   global Internet, it can no longer maintain a tunnel with its home


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   agent.  Thus all mobile network nodes that made use of the mobile
   router will lose their connectivity to the global network as well.
   This is hardly desirable, since there may exits another mobile router
   on the same network that has an active link to the global Internet.

   Mobile network nodes may eventually realize that their default router
   no longer has a route to the global network, and select an alternate
   mobile router as their default router.  Such a scheme relies on the
   mobile network nodes to perform their own route discovery.  It adds
   processing load to mobile network nodes, which may have very limited
   processing powers (e.g. embedded devices), and incurs additional
   delays (for the mobile network nodes to realize their current default
   route is down). In addition, different mobile routers will advertise
   different subnet prefixes, and thus when mobile nodes eventually
   switch their default routers, they will have to use different care-
   of-addresses.  This requires sending of binding updates to their
   home-agents, further increasing the lag of recovery.


































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3.  Using Multi-Homing Features in Bi-Directional Tunnels

   In order to utilize the additional robustness provided by multi-
   homing, mobile routers that employ bi-directional tunneling with
   their home agents should dynamically change their tunnel exit points
   depending on the link status.  For instance, if a mobile router
   detects that one of its egress interface is down, it should detect if
   any other alternate route to the global Internet exists.  This
   alternate route may be provided by any other mobile routers connected
   to one of its ingress interfaces that has an independent route to the
   global Internet, or by another active egress interface the mobile
   router it self possess.  If such an alternate route exists, the
   mobile router should re-establish the bi-directional tunnel using
   this alternate route.

   In the remaining part of this section, we will attempt to investigate
   methods of performing such re-establishment of bi-directional
   tunnels.  It is not the objective of this memo to specify a new
   protocol specifically tailored to provide this form of re-
   establishments.  Instead, we will limit ourselves to currently
   available mechanisms specified in Mobile IPv6 and Neighbour Discovery
   in IPv6 [19].


3.1.  Detecting Presence of Alternate Routes

   To actively utilize the robustness provided by multi-homing, a mobile
   router must first be capable of detecting alternate routes.  This can
   be manually configured into the mobile router by the administrators
   if the configuration of the mobile network is relatively static.  It
   is however highly desirable for mobile routers to be able to discover
   alternate routes automatically for greater flexibility.

   The case where a mobile router possesses multiple egress interface
   (bound to the same home agent or otherwise) should be trivial, since
   the mobile router should be able to "realize" it has multiple routes
   to the global Internet.

   In the case where multiple mobile routers are on the mobile network,
   each mobile router has to detect the presence of other mobile router.
   A mobile router can do so by listening for Router Advertisement
   message on its *ingress* interfaces. When a mobile router receives a
   Router Advertisement message with a non-zero Router Lifetime field
   from one of its ingress interfaces, it knows that another mobile
   router which can provide an alternate route to the global Internet is
   present in the mobile network.




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3.2.  Re-Establishment of Bi-Directional Tunnels

   When a mobile router detects that the link be which its current bi-
   directional tunnel with its home agent is using is down, it needs to
   re-establish the bi-directional tunnel using an alternate route
   detected.  We consider two separate cases here: firstly, the
   alternate route is provided by another egress interface that belongs
   to the mobile router; secondly, the alternate route is provided by
   another mobile router connected to the mobile network.   We refer to
   the former case as an alternate route provided by an alternate egress
   interface, and the latter case as an alternate route provided by an
   alternate mobile router.

3.2.1.  Using Alternate Egress Interface

   When an egress interface of a mobile router loses the connection to
   the global Internet, the mobile router can make use of its alternate
   egress interface should it possess multiple egress interfaces. The
   most direct way to do so is for the mobile router to send a binding
   update to the home agent of the failed interface using the care-of-
   address assigned to the alternate interface in order to re-establish
   the bi-directional tunneling using the care-of-address on the
   alternate egress interface.  After a successful binding update, the
   mobile router encapsulates outgoing packets through the bi-
   directional tunnel using the alternate egress interface.

   The idea is to use the global address (most likely a care-of-address)
   assigned to an alternate egress interface as the new (back-up) care-
   of-address of the mobile router to re-establish the bi-directional
   tunneling with its home agent.

3.2.2.  Using Alternate Mobile Router

   When the mobile router loses a connection to the global Internet, the
   mobile router can utilize a route provided by an alternate mobile
   router (if one exists) to re-establish the bi-directional tunnel with
   its home agent.  First, the mobile router has to obtain a care-of-
   address from the alternate mobile router (i.e. attaches itself to the
   alternate mobile router).  Next, it sends binding update to its home
   agent using the care-of-address obtained from the alternate mobile
   router From then on, the mobile router can encapsulates outgoing
   packets through the bi-directional tunnel using via the alternate
   mobile router.

   The idea is to obtain a care-of-address from the alternate mobile
   router and use this as the new (back-up) care-of-address of the
   mobile router to re-establish the bi-directional tunneling with its
   home agent.



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   Note that every packet sent from/to mobile network nodes to/from
   their correspondent nodes will experience two levels of encapsulation.
   First level of tunneling is done between a mobile router which the
   mobile network node uses as its default router and the mobile
   router's home agent.  The second level of tunneling is done between
   the alternate mobile router and its home agent.


3.3.  To Avoid Tunneling Loop

   The method of re-establishing the bi-directional tunnel as described
   in Section 3.2 may lead to infinite loops of tunneling.  This happens
   when two mobile routers on a mobile network lose connection to the
   global Internet at the same time and each mobile router tries to re-
   establish bi-directional tunnel using the other mobile router.  We
   refer to this phenomenon as tunneling loop.

   One approach to avoid tunneling loop is for a mobile router that has
   lost connection to the global Internet to insert an option into the
   Router Advertisement message it broadcasts periodically.  This option
   serves to notify other mobile routers on the link that the sender no
   longer provides global connection.  Note that setting a zero Router
   Lifetime field will not work well since it will cause mobile network
   nodes that are attached to the mobile router to stop using the mobile
   router as an access router too  (in which case, things are back to
   square one).


3.4.  Other Considerations

   When a mobile network is multi-homed, mobile network nodes may
   receive Router Advertisements that advertise different network
   prefixes.  This is usually the case when the multi-homed mobile
   network has two or more mobile routers advertising different routes
   to the global Internet.  It may also occur when the mobile network
   has only one mobile router with multiple egress interfaces bound to
   different home agents.  In these situations, mobile network nodes
   typically only select one to form its global (possibly care-of)
   address.

   In view of this, it may be desirable for mobile network node to be
   able to acquire "preference" information on each mobile network
   prefix from the mobile routers.  This allows default address
   selection mechanism such as that specified in [20] to be used.
   Further exploration on setting such "preference" information in
   Router Advertisement based on performance of the bi-directional
   tunnel might prove to be useful.



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4.  Security Considerations

   Currently the following security threat is identified with multi-
   homing in NEMO:

    - A malicious node in a mobile network advertises an Router
      Advertisement message with a non-zero Router Lifetime field,
      tricking mobile network nodes and even mobile routers to forward
      all packets through it.

   This is not specific to the multi-homing approach described in this
   document.  However, an authentication mechanism that can authenticate
   a mobile router from mobile network node when it attaches may be able
   to prevent such attacks.


References

   [1]  Bradner, S., "The Internet Standards Process -- Revision 3",
        BCP 9, RFC 2026, October 1996.

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

   [3]  Soliman, H., and Pettersson, M., "Mobile Networks (MONET)
        Problem Statement and Scope", Internet Draft, draft-soliman-
        monet-statement-00.txt, Work In Progress, Feb 2002.

   [4]  Ernst, T. et. al., "Network Mobility Support Requirements",
        Internet Draft, draft-ietf-nemo-requirements-00.txt, Work In
        Progress, Feb 2003.

   [5]  Lach, H. et. al., "Mobile Networks Scenarios, Scope and
        Requirements", Internet Draft, draft-lach-monet-requirements-
        00.txt, Work In Progress, Feb 2002.

   [6]  Kniventon, T. J., and Yegin, A. E., "Problem Scope and
        Requirements for Mobile Networks Working Group", Internet
        Draft, draft-kniventon-monet-requiremetns-00.txt, Work In
        Progress, Feb 2002.

   [7]  Perkins, C. E. et. al., "IP Mobility Support", IETF RCF 2002,
        Oct 1996.

   [8]  DARPA, "Internet Protocol", IETF RFC 791, Sep 1981.




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   [9]  Johnson, D. B., Perkins, C. E., and Arkko, J., "Mobility
        Support in IPv6", Internet Draft: draft-ietf-mobileip-ipv6-
        19.txt, Work In Progress, Oct 2002.

   [10] Deering, S., and Hinden, R., "Internet Protocol, Version 6
        (IPv6) Specification", IETF RFC 2460, Dec 1998.

   [11] Simpson, W., "IP in IP Tunneling", IETF RFC 1853, Oct 1995.

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

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

   [14] 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, Oct
        2002.

   [15] Thubert, P., and Molteni, M., "IPv6 Reverse Routing Header and
        Its Application to Mobile Networks", Internet Draft: draft-
        thubert-nemo-reverse-routing-header-01.txt, Work In Progress,
        Oct 2002.

   [16] Ernst, T., Castelluccia, C., Bellier, L., Lach, H., and
        Olivereau, A., "Mobile Networks Support in Mobile IPv6 (Prefix
        Scope Binding Updates)", Internet Draft: draft-ernst-mobileip-
        v6-network-03.txt, Work In Progress, Mar 2002.

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

   [18] Ernst, T., and Lach, H., "Network Mobility Support
        Terminology", Internet Draft, draft-ernst-nemo-terminology-
        00.txt, Work In Progress, Oct 2002.

   [19] Narten, T., Nordmark, E., and Simpson, W., "Neighbour Discovery
        for IPv6", IETF RFC 2461, Dec 1998.

   [20] Draves, R., "Default Address Selection for IPv6", draft-ietf-
        ipv6-default-addr-select-09.txt, Work in progress.





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Internet-Draft       Multi-homing Issues in NEMO          February 2003


Author's Addresses

   Chan-Wah Ng
   Panasonic Singapore Laboratories Pte Ltd
   Blk 1022 Tai Seng Ave #04-3530
   Tai Seng Industrial Estate
   Singapore 534415
   Phone: (+65) 6554 5420
   Email: cwng@psl.com.sg

   Takeshi Tanaka
   R&D center
   Panasonic Mobile Communications Co., Ltd.
   5-3, Hikarinooka, Yokoshuka-shi, Kanagawa
   239-0847, Japan
   Phone: +81-46-840-5494
   Email: Takeshi.Tanaka@yrp.mci.mei.co.jp


































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