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Versions: 00 01 02 03                                                   
Internet Draft                                         A. Petrescu, ed.
Document: draft-petrescu-nemo-mrha-00.txt           M. Catalina-Gallego
Expires: April 2003                                        C. Janneteau
                                                             H. Y. Lach
                                                           A. Olivereau
                                                               Motorola

                                                           October 2002


           Issues in Designing Mobile IPv6 Network Mobility
              with the MR-HA Bidirectional Tunnel (MRHA)
                 <draft-petrescu-nemo-mrha-00.txt>


Status of this Nemo

   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.

Abstract

   This document presents various issues related to designing a
   network mobility solution with Mobile IPv6 and the MRHA
   bidirectional tunnel.  Several scenarios are presented with the MR
   at home and in a visited network, from which an argumentation is
   made that all routing information is available in the HA (when BR
   and HA are co-located) or can be communicated by ICMP Redirect
   (when the BR and HA are separated).  This raises questions on when
   does the adding of more information than the 'R' bit into the
   Mobile IPv6 BUs is necessary.  Other generic issues with an MRHA
   solution, like link-local addresses in Mobile IPv6, router
   renumbering, or ND for the MR are presented.  Route Optimization
   and security aspects are only briefly touched.









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Table of Contents

   Status of this Memo................................................i
   Abstract...........................................................i
   Conventions used in this document..................................1
   1. Introduction....................................................1
     1.1 Prior descriptions...........................................3
   2. Definitions.....................................................3
   3. Data structures.................................................4
   4. Description of a Home Network...................................5
   5. Scenarios.......................................................6
     5.0 Manual mobile networks.......................................6
     5.1 Scenarios with co-located HA and BR..........................7
     5.2 Scenarios with HA and BR separated..........................11
     5.3 MR Redirects to BR..........................................15
   6. Informing the HA about the route to MR.........................16
     6.1 ICMP Redirect from BR to HA.................................16
     6.2 Static route method.........................................17
     6.3 Dynamic route method........................................18
   7. Other Issues...................................................18
     7.1 Link-local addresses........................................18
     7.2 MR as an MN.................................................19
     7.3 Prefix-based routing and host-based routing.................19
     7.4 Multicast subscriptions of the MR...........................19
     7.5 Neighbour Discovery for MR..................................19
     7.6 Separation of routing and mobility for MR...................20
     7.7 Router Renumbering..........................................20
   8. Mobile Router behaviour........................................21
     8.1 CoA Configuration...........................................21
     8.2 Discovering HA..............................................21
     8.3 Sending BUs to HA...........................................22
     8.4 Search order in various tables..............................22
   9. Home Agent behaviour...........................................22
   10. Route Optimization............................................22
   11. Security Considerations.......................................23
     11.1 Security of the MRHA tunnel................................23
     11.2 Security for Route Optimization............................23
   Acknowledgements..................................................24
   Changes...........................................................24
   References........................................................24
   Authors' Addresses................................................26

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 [1].

1. Introduction

   This document identifies issues when designing an enhancement of
   the Mobile IPv6 protocol to support mobile networks.  The
   background is the extensive use of the bidirectional tunnel between
   MR and HA.  The HA acts on behalf of the link-local address of the

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   moving interface of the Mobile Router when the MR is in a foreign
   network.

   The Mobile Router is using BUs and BAcks with the Home Agent to
   maintain the MRHA bidirectional tunnel.  The modifications to
   Mobile IPv6 HA and MN are minimal.  The BU format contains, in
   addition to all Mobile IPv6 fields, an additional bit 'R' that
   informs the HA that this is a mobile router instead of a mobile
   host.  The 'R' bit is used by the HA to perform certain tasks
   differently for this home address than if it were a host.

   Traffic coming from outside the home link, or from other hosts on
   the home link, and directed to hosts behind the mobile router
   normally only need to go through the L2 address of the mobile
   router's correspoinding to its L3 address.  With Proxy ND [19], it
   is the HA that pretends to own MR's L3 address by advertising new
   associations of of the MR's L3 address to the HA's L2 address, thus
   intercepting MR's home traffic and forwarding it to the current CoA
   of the MR.

   When the MR is in a foreign network, traffic coming from the mobile
   network and towards anywhere to the Internet, is first forwarded by
   the MR through the reverse tunnel MRHA to the HA.  Then HA
   decapsulates and forwards to the specific host on the home link or
   outside the home link.

   When the MR acts as a mobile host, vanilla Mobile IPv6 is used.  MR
   can send both BUs with the R bit set and without the R bit set.
   Depending on what is decided for the home address to be like
   (link-local or other), the HA could deduce both.

   A nemo solution with the MRHA tunnel should allow for a clean
   separation between routing maintenance and mobility bindings
   maintenance.  The route maintenance is done unmodified between MR
   and BR, while the mobility bindings are done unmodified between MR
   and HA.

   Much of the argumentation made around routing can be considered as
   operator, or administrative issues, which seen otherwise can
   discard some of the conclusions, but not all.

   The document is organized as follows: the next sections present a
   description of the home network, where the HA could be co-located
   with the BR, or separated.  Then a set of simple scenarios are
   presented describing the normal routing behaviour of the MR when it
   is at home, and the desired behaviour of routing and of ND
   messaging at home, when the MR is in a foreign network.  These
   scenarios are presented such that they expose the need for new
   behaviours only in the case where the HA is separated from the BR;
   otherwise (HA/BR co-located), all routing information is already
   present in the HA.  The following section presents possible
   approaches for adding to HA routing information related to MR, one
   based on ICMP Redirects, one based on static or dynamic routes
   (from previous documents) and a third approach as a slight


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   modifications of dynamic routing where the HA "only listens" to
   route updates but doesn't advertise.

   Additional sections present other issues related to maintaining
   normal MR behaviour when it is not at home (e.g. renumbering or
   multicast subscriptions) and then detailed behaviour of the HA and
   of the MR.  The Route Optimization problem and the Security
   Considerations are briefly touched at the end.

1.1 Prior descriptions of mobile network support with Mobile IPv6

   A complete description of the previous proposals to support mobile
   networks or mobile routers with Mobile IP bi-directional tunnel can
   not be made here due to space constraints.

   The closest description to mobile network support in Mobile IPv6
   with the MRHA tunnel can be found in [13].  The approach described
   in that document relies on the bidirectional tunnel between MR and
   HA.  The solution proposed is valid for Mobile IPv6 as for Mobile
   IPv4.  The MR and HA behaviours still represent a sensitive
   departure from the Mobile IPv6 protocol in that MR informs its HA
   directly about the tunnel interface and dynamically triggers
   additions of routing table entries in the HA's routing table for
   the MR's tunnel.  In addition, the most recent version of the draft
   proposes usage of the PSBUs in order to inform the HA about the
   prefix of the mobile network (thus a combination with the PSBU
   approach).  Moreover, the considerations about dynamic routing in
   this draft refer only to how dynamic routing would work with a MR,
   but not about the necessity of running a routing protocol between
   HA and MR.  See sections 6.2 and 6.3 for an overview of the methods
   presented in these documents.

   Using PSBUs as proposed in [8] and [13] has many other side-effects
   not considered until recently.  When the mobile network is assigned
   several prefixes instead of one, then it is not clear whether
   several BUs are being sent or only one with several prefixes
   inside.  Remark that in the vanilla Mobile IPv6 case, only one CoA
   can be sent with a BU (the alternative CoA is only an alternative
   not a substitute).

   In the Mobile IPv4 case, the network mobility support with the MRHA
   tunnel has been reported at least by various teams at Cisco [4] and
   NASA [14].



2. Definitions

   Many relevant definitions for network mobility with the MRHA (could
   me spelled emra) tunnel can be found in [9].  In addition to those
   definitions:

   MRHA bidirectional tunnel, sometimes referred to as a reverse
   tunnel.  As described in [6], [12], [17], [20].


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   MIMR: the Mobile Interface of the Mobile Router: the interface that
   connects MR to the home link and that changes its Care-of Address
   when away from home.

   MR_HoA: mobile router's Home Address, or the home address of the
   MIMR.

   MNP: mobile network prefix, or the prefix of the link of the mobile
   network that will move away.  Note that in the most general case a
   single MR may route multiple prefixes, in which case there would be
   multiples MNPs per one mobile network.

   FN: fixed node on the home link.  It doesn't stand for fixed
   network.

3. Data structures

   A home agent that supports mobile networks maintains the following
   structures: destination cache [19], binding cache [12] and routing
   table [11].  The binding cache is modified from Mobile IPv6, such
   that.  The Home Agent also maintains the MRHA Tunnel Table.

   A Mobile Router contains an on-link prefix list, a neighbour cache,
   a destination cache, routing table, a binding update list, a home
   agents list and so on.

   Additionally, it contains an MRHA Tunnel Table with the following
   fields:
         -interface number
         -address of the tunnel endpoint corresponding to the mobile
          router.  This is normally a CoA.
         -address of the tunnel endpoint corresponding to the home
          agent.  This is normally the HA address.
         -list of entries present in the neighbour cache.
         -list of entries present in the destination cache.
         -list of entries present in the prefix list.
         -list of entries present in the default router list.
         -list of entries present in every other structure.

   The idea behind the MRHA tunnel table is to have as little
   modifications as possible to the other ND and Mobile IPv6 tables
   such that the MR acts as if it were at home, but across the MR-HA
   tunnel.


   All the mechanisms related to ND and classic routing are being
   subjected to this tunnel table, such as to allow for mobility of
   the mobile network.  One example is to stop doing ND for the home
   address of the MR's interface that acquired a new CoA.  It also
   prevents the MR to have routing interactions with the visited
   domain, but it alows it to continue having "normal" routing
   interactions with its home domain, including exchanging of normal
   dynamic routing messages, multicast routing messages, ICMP
   redirects and others.


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4. Description of a Home Network

   When designing a NEMO solution with the MRHA tunnel, the first
   steps are to carefully consider the actual behaviour of the home
   network when the mobile network is at home, employing normal
   routing.  Then this behaviour should be maintained as much as
   possible when the MR is not at home (e.g. MR should be able to send
   redirects through the MRHA tunnel); reciprocically, the normal
   behaviour of an FR at home should change when that FR is an MR and
   is at home (e.g. when MR at home, the MRHA tunnel should be torn
   down).  When the MR is in a foreign network, its presence at home
   is simulated by the HA (as in Mobile IPv6 for hosts).

   Let us consider a simple case of a home network that supports
   movement of one of its links.  The home network is made up of a
   home link and a mobile network link, separated by the Mobile
   Router.  The home network is connected to the Internet via the
   Border Router, as presented in the figure:
                             ----
                            | FN |
                             ----
                               |               -------
                 home link -------------------| HA/BR |---> Internet
                               |               -------
                             ----    -----
                            | MR |  | LFN |
                             ----    -----
                               |       |
                   mobile link ---------

   Current specification for Mobile IPv6 implies that the HA can be
   either co-located with the BR, or it can act as a separate
   one-interface machine (this is advantageous for deploying Mobile
   IPv6 without changing BRs).  For mobile networks, the latter mode
   can be pictured like this:
                             ----    ----
                            | FN |  | HA |
                             ----    ----
                               |       |       ----
                 home link -------------------| BR |------> Internet
                               |               ----
                             ----    -----
                            | MR |  | LFN |
                             ----    -----
                               |       |
           mobile network link ---------

   It is assumed that routes outside the home link are managed by BR
   and MR, either in a static manner (operator fills in routing
   tables) or dynamic manner (application software partially manages
   routing tables).  Remark that even when the dynamic style is used,
   it is still true that operator fills initial routing configuration
   files, where she/he puts the image of the network as being what the
   operator believes it to be.  The dynamic behaviour of routing
   protocols intervenes when certain links come down or up due to

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   failures, the operator view is no longer true, and the routers
   manage to find alternative paths.  Also, the dynamic behaviour
   helps obtaining shortest paths over large networks, relying on
   several local operator's views of smaller sized networks.  Addition
   of mobility should not change this.

   If static routing is used instead of dynamic routing, then static
   routes are added manually both on MR and on the BR.  When
   considering adding *static* routes in a *dynamic* manner for
   prefixes shorter than /128 by Mobile IP, authors of this document
   realize (in truth, hopefully) that Mobile IP starts using semantics
   that are traditionally belonging to routing protocols.

5. Scenarios

   For the sake of completetess, we first describe a simple "manual"
   scenario for mobile networks based on the MRHA tunnel, that exposes
   relative simplicity, that uses static routing and doesn't use
   Mobile IP.

   Then, adding the Mobile IP behaviour, we present detailed scenarios
   of communication between an FN on the home link and an LFN on the
   mobile network link and a CN on the Internet, when the mobile
   network is at home and away from home in a visited network, and
   when the HA is co-located with the BR and separated from the BR.
   All in all, 16 simple scenarios are presented.

   The scenarios where HA is co-located with BR (1 up to 8) expose
   that there is no need for MR to communicate prefixes to its HA via
   BUs.  In a normal routing function, when the MR is at home, it
   exchanges routing information with the BR (co-located with the HA)
   and thus those prefixes are communicated by e.g. RIP or OSPF.  When
   the MR is not at home, this behaviour continues, but through the
   MRHA tunnel.

   The scenarios where HA and BR are separated (9 up to 16) expose
   that HA needs an entry in its routing table in order to be capable
   of forwarding packets to the MR (when it is not at home).

   An additional scenario is then presented where MR at home is using
   ICMP Redirect, a functionality that might be needed even when the
   MR is not at home.


5.0 Manual mobile networks

   Authors of this draft have experimented with "manual" mobile
   networks in IPv4, where the addition of routes and tunnels on the
   MR and on the BR are done manually, by operators talking on the
   phone.

   A home network was used that contains about 10 routers and about 12
   subnets.  That home network is connected to the Internet with a BR.
   All routers have static routes among them.


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   Then, one slice of that home network (the mobile network)
   containing one "MR", one normal router and 6 subnets, was
   disconnected from home, and moved across the Atlantic.  Once the
   "MR" was connected on the other side, it was manually configured
   with a new IPv4 address, mask and default route.  Then a tunnel
   interface and a route were manually set up on the MR, a tunnel
   interface and a route were manually set up on the BR.  All other
   routes on all other routers where not touched.  Mobile IP software
   was not used.

   The entire network (the home and the mobile network) looked, and
   acted, as if the mobile slice were at home.  During this, several
   applications were tested between hosts in the mobile network, hosts
   in the home network and hosts on the Internet (incidentally, one of
   the applications was relying on Mobile IPv4 for hosts, but in no
   relation with the mobile network moving).

   Again, this "manual" mobile networks scenario was not using any
   dynamic routing protocol, and the tunnel was not supporting any
   form of broadcast of multicast.

5.1 Scenarios with co-located HA and BR

   1. FN sends packet to LFN, mobile network home, HA/BR colocated
                             ----
                            | FN |
                             ----
                               |               -------
                 home link -------------------| HA/BR |---> Internet
                               |               -------
                             ----    -----
                            | MR |  | LFN |
                             ----    -----
                               |       |
                   mobile link ---------

   -FN scans its routing table for LFN's address, and finds default
    route towards BR (if towards MR, see section 6.1).
   -FN sends NS for L2 address of BR.
   -BR replies NA.
   -FN sends packet to BR.
   -BR scans its routing table for LFN's address, and finds route
    through MR;
   -BR sends NS for MR.
   -MR replies NA with its L2 address.
   -BR forwards packet to MR and sends ICMP Redirect to FN such that
    subsequent packets from FN to LFN go straight through MR and not
    through BR.
   -MR forwards packet to FN.

   The sensitive issue exposed here is the way in which initially the
   packet travels from FN to BR to MR, the dynamic addition of an
   entry in the routing table of the FN (even if FN doesn't run a
   routing protocol) and that subsequent packets will not go through
   BR, but from FN to MR to LFN.

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   2. FN sends packet to LFN, mobile network visits, HA/BR colocated
     ----                                   /
    | FN |                                 /
     ----                       ----------/
       |            -------    |          |
   ----------------| HA/BR |---| Internet |
         home link  -------    |          |
                                ----------\
                                           \
                                            \   ----  Visited link
                                             --| AR |------
                                                ----     |
                                                         |
                                                       ----    -----
                                                      | MR |  | LFN |
                                                       ----    -----
                                                         |       |
                                                         ---------
                                                         mobile net

   -FN scans its routing table for LFN's address, and finds default
    route towards BR.
   -FN sends NS for L2 address of BR.
   -BR replies NA.
   -FN sends packet to BR.
   -BR scans its routing table for LFN's address, and finds route
    through MR;
   -BR (being an HA) scans its BC and its routing table and finds it
    needs to encapsulate this packet towards MR's CoA.
   -BR encapsulates through the MRHA tunnel to MR's CoA.
   -MR decapsulates and forwards to LFN.

   3. LFN sends packet to FN, mobile network home, HA/BR colocated
                             ----
                            | FN |
                             ----
                               |               -------
                 home link -------------------| HA/BR |---> Internet
                               |               -------
                             ----    -----
                            | MR |  | LFN |
                             ----    -----
                               |       |
                   mobile link ---------

   -LFN scans its routing table for FN's address, and finds default
    route towards MR.
   -LFN sends NS for L2 address of MR.
   -MR replies NA.
   -LFN sends packet to MR.
   -MR scans its routing table for LFN's address, and finds route
    'on-link';
   -MR sends NS for FN.
   -FN replies NA with its L2 address.
   -MR forwards packet to FN.

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   4. LFN sends packet to FN, mobile network visits, HA/BR colocated
     ----                                   /
    | FN |                                 /
     ----                       ----------/
       |            -------    |          |
   ----------------| HA/BR |---| Internet |
         home link  -------    |          |
                                ----------\
                                           \
                                            \   ----  Visited link
                                             --| AR |------
                                                ----     |
                                                         |
                                                       ----    -----
                                                      | MR |  | LFN |
                                                       ----    -----
                                                         |       |
                                                         ---------
                                                         mobile net

   -LFN scans its routing table for FN's address, and finds default
    route towards MR.
   -LFN sends NS for L2 address of MR.
   -MR replies NA.
   -LFN sends packet to MR.
   -MR encapsulates this packet through the MRHA tunnel and sends to
    HA.
   -HA receives this packet and decapsulates.
   -HA scans its routing table for FN's address, and finds route
    'on-link';
   -HA sends NS for FN.
   -FN replies NA with its L2 address.
   -HA forwards packet to FN (on behalf of the MR).

   5. CN sends packet to LFN, mobile network home, HA/BR co-located
                                                ----  CN link
                                             --| BR1|------
                                            /   ----     |
                                           /             |
                                ----------/            ----
                    -------    |          |           | CN |
   ----------------| HA/BR |---| Internet |            ----
       | home link  -------    |          |
     ----    -----              ----------\
    | MR |  | LFN |                        \
     ----    -----                          \
       |       |
       ---------
     mobile net link

   -BR receives packet from CN towards LFN.
   -BR scans its routing table and finds dest through MR.
   -BR sends NS for L2 address of MR and MR replies NA.
   -BR forwards packet to MR.
   -MR forwards packet to LFN.

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   6. CN sends packet to LFN, mobile network visits, HA/BR colocated

                                                 ----  CN link
                                              --| BR1|------
                                             /   ----     |
                                            /             |
                                 ----------/            ----
                     -------    |          |           | CN |
                 ---| HA/BR |---| Internet |            ----
                     -------    |          |
                                 ----------\
                                            \
                                             \   ----  Visited link
                                              --| AR |------
                                                 ----     |
                                                          |
                                                        ----    -----
                                                       | MR |  | LFN |
                                                        ----    -----
                                                          |       |
                                                          ---------
                                                          mobile net
   -BR receives packet from CN towards LFN.
   -BR scans its routing table and finds dest through MR.
   -BR scans its routing table and its BC and realizes it needs to
    send this through the MRHA tunnel.
   -BR sends the packet through the MRHA tunnel to MR.
   -MR decapsulates and forwards to LFN.

   (this is sometimes referred to as triangular routing, since the
    packet from CN to LFN travels artificially through BR)


   7. LFN sends packet to CN, mobile network home, HA/BR colocated


                                                ----  CN link
                                             --| BR1|------
                                            /   ----     |
                                           /             |
                                ----------/            ----
                    -------    |          |           | CN |
   ----------------| HA/BR |---| Internet |            ----
       | home link  -------    |          |
     ----    -----              ----------\
    | MR |  | LFN |                        \
     ----    -----                          \
       |       |
       ---------
     mobile net link

   -MR receives packet from LFN towards CN.
   -MR scans its routing table to and finds dest through BR.
   -BR forwards packet to Internet towards CN.
   -BR1 forwards packet to CN.

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   8. LFN sends packet to CN, mobile network visits, HA/BR colocated
                                                 ----  CN link
                                              --| BR1|------
                                             /   ----     |
                                            /             |
                                 ----------/            ----
                     -------    |          |           | CN |
                 ---| HA/BR |---| Internet |            ----
                     -------    |          |
                                 ----------\
                                            \
                                             \   ----  Visited link
                                              --| AR |------
                                                 ----     |
                                                          |
                                                        ----    -----
                                                       | MR |  | LFN |
                                                        ----    -----
                                                          |       |
                                                          ---------
                                                          mobile net
   -MR receives packet from LFN towards CN.
   -MR scans its tables and finds it needs to send it through the MRHA
    tunnel.
   -BR receives this packet, decapsulates and forwards to Internet.
   -BR1 forwards this packet to CN.

   (this is sometimes referred to as triangular routing, since the
    packet from LFN to CN travels artificially through BR)

5.2 Scenarios with HA and BR separated

   9. FN sends packet to LFN, mobile network home, HA separated BR
                             ----    ----
                            | FN |  | HA |
                             ----    ----
                               |       |       ----
                 home link -------------------| BR |------> Internet
                               |               ----
                             ----    -----
                            | MR |  | LFN |
                             ----    -----
                               |       |
           mobile network link ---------


   -FN scans its routing table for LFN's address, and finds default
    route towards BR.
   -FN sends NS for L2 address of BR.
   -BR replies NA.
   -FN sends packet to BR.
   -BR scans its routing table for LFN's address, and finds route
    through MR;
   -BR sends NS for MR.
   -MR replies NA with its L2 address.

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   -BR forwards packet to MR and sends ICMP Redirect to FN such that
    subsequent packets from FN to LFN go straight through MR and not
    through BR.
   -MR forwards packet to FN.


   10. FN sends packet to LFN, mobile network visits, HA separated BR


     ----    ----                           /
    | FN |  | HA |                         /
     ----    ----               ----------/
       |       |       ----    |          |
   -------------------| BR |---| Internet |
         home link     ----    |          |
                                ----------\
                                           \
                                            \   ----  Visited link
                                             --| AR |------
                                                ----     |
                                                         |
                                                       ----    -----
                                                      | MR |  | LFN |
                                                       ----    -----
                                                         |       |
                                                         ---------
                                                         mobile net


   -FN scans its routing table for LFN's address, and finds default
    route towards BR.
   -FN sends NS for L2 address of BR.
   -BR replies NA.
   -FN sends packet to BR.
   -BR scans its routing table for LFN's address, and finds route
    through MR;
   -BR sends NS for MR.
   -HA replies NA with its L2 address (on behalf of MR).
   -BR forwards packet to HA and sends ICMP Redirect to FN such that
    subsequent packets from FN to LFN go straight through MR and not
    through BR.  BR also sends ICMP Redirect to HA, such that HA knows
    a route through MR.  The logic of this last ICMP Redirect is
    described in section 6.1.
   -HA scans its routing table for LFN's address, and finds through MR;
   -HA scans binding cache and finds 'through MRHA tunnel';
   -HA encapsulates and sends packet to MR.
   -MR decapsulates and forwards to LFN.


   The problem in the above case is how to inform the HA about the
   route towards MR.  When MR at home, and HA being a host, normally
   HA doesn't have a route towards MR.  See discussion in section 6.1.




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   11. LFN sends packet to FN, mobile network home, HA separated BR
                             ----    ----
                            | FN |  | HA |
                             ----    ----
                               |       |       ----
                 home link -------------------| BR |------> Internet
                               |               ----
                             ----    -----
                            | MR |  | LFN |
                             ----    -----
                               |       |
           mobile network link ---------

   -LFN scans its routing table for FN's address, and finds default
    route towards MR.
   -LFN sends NS for L2 address of MR.
   -MR replies NA.
   -LFN sends packet to MR.
   -MR scans its routing table for LFN's address, and finds route
    'on-link';
   -MR sends NS for FN.
   -FN replies NA with its L2 address.
   -MR forwards packet to FN.

   12. LFN sends packet to FN, mobile network visits, HA separated BR
     ----    ----                           /
    | FN |  | HA |                         /
     ----    ----               ----------/
       |       |       ----    |          |
   -------------------| BR |---| Internet |
         home link     ----    |          |
                                ----------\
                                           \
                                            \   ----  Visited link
                                             --| AR |------
                                                ----     |
                                                         |
                                                       ----    -----
                                                      | MR |  | LFN |
                                                       ----    -----
                                                         |       |
                                                         ---------
                                                         mobile net

   -LFN scans its routing table for FN's address, and finds default
    route towards MR.
   -LFN sends NS for L2 address of MR. MR replies NA.
   -LFN sends packet to MR.
   -MR encapsulates this packet through the MRHA tunnel and sends to
    HA.
   -HA receives this packet and decapsulates.
   -HA scans its routing table for FN's address, and finds route
    'on-link';
   -HA sends NS for FN.  FN replies NA with its L2 address.
   -HA forwards packet to FN (on behalf of the MR).

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   13. CN sends packet to LFN, mobile network home, HA separated BR

                                                ----  CN link
                                             --| BR1|------
             ----                           /   ----     |
            | HA |                         /             |
             ----               ----------/            ----
               |       ----    |          |           | CN |
     -----------------| BR |---| Internet |            ----
       | home link     ----    |          |
     ----    -----              ----------\
    | MR |  | LFN |                        \
     ----    -----                          \
       |       |
       ---------
     mobile net link

   -BR receives packet from CN towards LFN.
   -BR scans its routing table to and finds dest through MR.
   -BR sends NS for L2 address of MR.
   -MR replies NA.
   -BR forwards packet to MR.
   -MR forwards packet to LFN.

   14. CN sends packet to LFN, mobile network visits, HA separated BR

                                                 ----  CN link
                                              --| BR1|------
              ----                           /   ----     |
             | HA |                         /             |
              ----               ----------/            ----
                |       ----    |          |           | CN |
              ---------| BR |---| Internet |            ----
                        ----    |          |
                                 ----------\
                                            \
                                             \   ----  Visited link
                                              --| AR |------
                                                 ----     |
                                                          |
                                                        ----    -----
                                                       | MR |  | LFN |
                                                        ----    -----
                                                          |       |
                                                          ---------
                                                          mobile net
   -BR receives packet from CN towards LFN.
   -BR scans its routing table to and finds dest through MR.
   -BR sends NS for L2 address of MR.  HA replies NA on behalf of MR.
   -BR sends Redirect to HA informing it about a route towards MR.
    See section 6.1 on a discussion about this ICMP Redirect.
   -Simultaneously with previous packet, BR forwards packet to HA.
   -HA scans its routing table and finds an entry to MR (added as a
    result to ICMP redirect), it also has a BC entry for MR, so it
    sends the packet through the MRHA tunnel.

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   The problem in the above case is how to inform the HA about the
   route towards MR.  When MR at home, and HA being a host, normally
   HA doesn't have a route towards MR.  See discussion in section 6.1.

   15. LFN sends packet to CN, mobile network home, HA separated BR

                                                ----  CN link
                                             --| BR1|------
             ----                           /   ----     |
            | HA |                         /             |
             ----               ----------/            ----
               |       ----    |          |           | CN |
   -------------------| BR |---| Internet |            ----
       | home link     ----    |          |
     ----    -----              ----------\
    | MR |  | LFN |                        \
     ----    -----                          \
       |       |
       ---------
     mobile net link

   -MR receives packet from LFN towards CN.
   -MR scans its routing table and finds dest through BR.
   -BR sends packet to CN

   16. LFN sends packet to CN, mobile network visits, HA separated BR
                                                 ----  CN link
                                              --| BR1|------
              ----                           /   ----     |
             | HA |                         /             |
              ----               ----------/            ----
                |       ----    |          |           | CN |
             ----------| BR |---| Internet |            ----
                        ----    |          |
                                 ----------\
                                            \
                                             \   ----  Visited link
                                              --| AR |------
                                                 ----     |
                                                          |
                                                        ----    -----
                                                       | MR |  | LFN |
                                                        ----    -----
                                                          |       |
                                                          ---------
                                                          mobile net
   -MR receives packet from LFN towards CN.
   -MR encapsulates this packet through the MRHA tunnel.
   -HA receives this packet, decapsulates and sends to CN.

5.3 MR Redirects to BR

   Also, consider the scenario where the FN has a default route
   towards the MR instead of the BR, and sending packets to a CN on
   the Internet.  This might very well happen when the MR is at home

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   and sending RAs, in addition to the RAs sent by the BR.  FN might
   configure a default route through the MR instead of the BR.  If MR
   is at home, MR will redirect the FN towards the BR.  So, even if
   this looks like a wrong configuration on the FN (its default route
   should point to BR and not MR), packets will still travel correctly
   when MR is at home.  This should be maintained when the MR is not
   at home.  There are two possibilities: either the HA (replacing the
   MR) redirects the FN towards the BR, or it is the MR itself that
   sends the respective ICMP redirect message to the FN (through the
   MRHA tunnel).  The first case supposes that HA maintains a routing
   table, which contains routes towards the mobile network.  This is
   less desirable if the HA is not co-located with BR, and where we
   prefer not to have routing interactions with the HA.  The latter
   case is more plausible, keeping the default routing behaviour to
   the MR.

6. Informing the HA about the route to MR

   In certain scenarios presented previously, with the HA dissociated
   from the BR and the MR in the visited network, there is a need for
   the HA to maintain in its routing table an entry towards the MR.  A
   scenario where packets from CN towards LFN are looping between MR
   and HA has been described in detail in section 3.2.4 of [8].
   Several solutions exist to avoid this looping, described below.

6.1 ICMP Redirect from BR to HA

   One alternative for avoiding the loop problem is by using ICMP
   Redirects [19] sent by BR to HA in order to communicate to HA the
   route it misses towards the MR.  ICMP Redirects are deployed and
   used in existing networks.  The classic behaviour of ICMP Redirects
   is presented in scenario 1.  Scenarios 10 and 14 with
   MR-not-at-home and BR dissociated from HA, present the fact that
   classic ICMP Redirects are not triggered normally and thus
   modifications are needed.

   In addition to the normal behaviour with ICMP Redirects, described
   in [19], it could be modified according to the following.  The
   decision by BR to send ICMP Redirect towards HA can be taken in at
   least three ways:

     -allow a number of iterations of a packet looping between HA and
      BR and after this fixed number decide to send the Redirect to HA
      such as the looping stops.  This modifies the normal behaviour
      of BR.

     -another possibility is for BR to react at the moment it receives
      the proxy NA from HA (on behalf of the MR), compare to the
      current entry it has in the Neighbour Cache for MR, and then
      decide that, because MR has moved away, send Redirect to HA to
      inform HA about the route to MR.  This is the route (or set of
      routes) normally maintained by the BR with the MR, doesn't
      contain any form of the new position (CoA) of the MR.  This
      route, or set of routes (in which case a set of Redirects are
      sent), is copied from MR's routing table.  All routes that have

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      destination the MR's home address need to be communicated to HA
      with ICMP Redirects.  This modifies the normal behaviour of BR.

     -yet another possibility is to consider modifications on HA (from
      vanilla Mobile IPv6), but don't touch BR, such that HA generates
      a new packet, thus obtaining a classic ICMP Redirect from BR.

      When the HA receives a packet that is not for itself, it
      encapsulates it with an IP-in-IP tunnel, having the src address
      its own address and the destination address copied from the dst
      address of the original packet.  Then try to route this packet
      and find the default route towards BR.  Then BR sends a normal
      ICMP Redirect informing HA there is a better route for this
      packet towards MR.  Thus HA acquires the MR route dynamically.
      The packet will be passed on by BR to HA again, and further
      details are needed here.  Remark that this is equivalent to one
      iteration of the loop (a particular case of the fixed iterations
      loop mentioned previously).

6.2 Static route method

   This is proposed by [4] and [13], where operator statically
   introduces a route in the HA, for MR's prefix, towards MR's
   address, or towards the specific MRHA tunnel.

   The first approach proposed in [4] suggests to configure a new
   static tunnel on the MR's HA towards MR_HoA.  This static tunnel,
   that we call here MR_HoA_tunnel, is to be used as output interface
   of a new static entry added in the routing table of HA for MR's
   prefix: MR prefix -> MR_HoA_tunnel.  Upon reception of a data
   packet from CN addressed to a LFN, MR's HA will consult its routing
   table and find a match for that packet for this static route since
   LFN address matches MR's prefix.  As a results it will encapsulate
   the packet with an additional header that will have MR's HA as
   source address and MR_HoA as destination address.  In order to
   forward this packet, now addressed to MR's Home Address, the MR
   will first consult its binding cache and discover MR's Care-of
   address.  It will thus send the packet through the MRHA tunnel
   towards MR's current location.  It is worth mentionning that this
   approach introduces a double encapsulation of an incoming packet to
   be forwarded to the MR: the first is due to the MR_HoA_tunnel, the
   second to the MRHA tunnel.

   The second approach proposed in [13] suggests a similar method but
   avoids the overhead introduced by the two tunnels.  It consists in
   configuring a static route in MR's HA routing table for MR's prefix
   towards MR's Home Address: MR prefix -> MR_HoA.  Upon reception of
   a data packet from CN addressed to a LFN, MR's HA will consult its
   routing table and, again, find a match for that packet for this
   static route since LFN address matches MR's prefix. This indicates
   the MR's HA that the packet should be routed towards MR_HoA.  From
   its binding cache it discovers MR's CoA and as a consequence
   forwards the incoming packet for CN directly through the MRHA
   tunnel.  This approach reduces the overhad of the MR_HoA_tunnel but
   requires a suitable coordination of the routing table and binding
   cache on the HA.
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   Analyzed from the perspective where HA is separated from BR, and
   where MR doesn't normally maintain routes with HA, then this
   addition might seem superfluous.  Consider a situation where MR and
   BR maintain routing information and where that manual route is
   added on HA.  When the MR is not at home, consider that
   administrator decides to add a new fixed subnet at home, with its
   own router neighbouring with BR on the home link.  Consider the new
   subnet's prefix being a longer prefix derived from the prefix
   assigned to the MR's subnet.  This is perfectly feasible by
   changing configurations on the MR and BR.  That can work perfectly
   even if MR is not at home.  But if HA doesn't participate in this
   exchange (which is the case if HA separated from BR) then the
   manual route added previously in the HA is no longer valid.  Thus,
   a potential issue.

   Further explanation or simplification needed here.

6.3 Dynamic route method

   It is possible for the HA, being either separated or co-located
   with the BR, to run a specific routing protocol, participating in
   the routing interactions between BR and all other neighbouring
   routers on the home link.  Thus, the HA always has the necessary
   route it needs to join the MR's network.

   If the HA is a one-interface machine, and separated from the BR, it
   seems that it maintains information that is not always necessary to
   its well working as a HA.  For example, it will maintain routes to
   all neighbouring routers, be it fixed or mobile.  The routes to the
   fixed neighbouring routers are not necessary for its working as a
   host, since it suffices to only have a default route towards a BR,
   that will normally dynamically Redirect it towards the other fixed
   routers.  Moreover, if HA runs a dynamic routing protocol, its
   route updates will never be taken into account by other routers,
   since they will always be one hop further than the routes already
   known by them.  Thus it might be possible to have the HA as a
   silent routing, only receiving route updates from the neighbouring
   routers, but never sending route updates, since it does not have a
   network behind it (it is a "host") whose reachability it needs to
   advertise.

   RIP [11] supports having a silent host that only listens to update
   messages, but does not advertise new routes.  With OSPF [18] the
   "listening only" requirement is complicated by the fact that the HA
   would needs to participate in OSPF's HELLO protocol.

   The advantage of using this solution is that it does not require
   additional changes to Mobile IPv6, and PSBUs are not needed.  The
   disadvantage is that if the MR does not run a routing protocol then
   we still need some way of telling the HA the routes to the MNPs,
   which gets us back to sections 6.1 and 6.2.

   Further explanation or simplification needed here.

7. Other Issues

7.1 Link-local addresses

   When the MR is at home, and if it runs a dynamic routing protocol,
   it exchanges routing information with BR, by using its link-local
   address and BR's link-local address.  When the MR is not at home,
   and HA defends the MR's home address, the HA is normally doing this
   for any type of addresses except link-locals.  The immediate
   necessity would be for the HA to defend a link-local address of the
   MR, instead of a global-scoped home address.  However, this is in
   conflict with the necessity of dynamic routing protocols to use
   link-local addresses only.

   If Mobile IPv6 spec is to be followed, then the HA will not allow
   re-direction of traffic of a Home Address towards a CoA, when that
   Home Address is link-local.

   Another issue concerning link local addresses: the MR has routes to
   the BR using BR's link local address.  When the MR is away from
   home: how does the MR reach BR's link local address?

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   How does it tell the difference between a link local address on the
   home link and a link local address on the visited link?

7.2 MR as an MN

   If the MR is at home and it has an address configured on the moving
   interface other than a link-local address, then the MR can act as
   an MH too, and send normal Mobile IPv6 BUs, binding that Home
   Address to a newly configured CoA; thus allowing the MR to be an MH
   for itself only, ignoring the LFNs.  If the MR at home doesn't have
   other addresses than link-local on the mobile interface then the MR
   can not send normal Mobile IPv6 BUs and can not be an MH.  It can
   however be an MR for the hosts on the mobile network.

7.3 Prefix-based routing and host-based routing

   Prefix-based hierarchical routing (where the mobile network link
   has a prefix that is a subset of the home-network link) is the
   preferred type of routing for IPv6.  Practically though, it is
   possible for the BR to have a routing table entry containing the
   prefix of the mobile network, as well as a host-based entry that
   points to a certain LFN also in the mobile network.  Those two
   entries might or might not have the same common sub-prefix.  With a
   MR at home, being a normal router, BR will know how to forward to
   all hosts behind the MR as well as only to the specific LFN of the
   host-based route.  This behaviour should be maintained when the MR
   is no longer at home and when it has a bidirectional tunnel MRHA.

7.4 Multicast subscriptions of the MR

   When the MR is at home, it normally joins certain multicast groups
   related to routing (e.g. all-routers multicast group with site
   scope).  This is assumed by dynamic routing protocols, or by
   renumbering mechanisms.  When the MR is no longer at home, its
   multicast subscription should continue as if it were at home.  This
   can be achieved by "home subscription" techniques considered in
   relation with Mobile IPv6.

7.5 Neighbour Discovery for MR

   When MR is at home and sends RA towards the home link, it should
   not advertise itself as being capable of being a default router
   (Router Lifetime should be 0).

   When the MR is visiting, it should not respond to RSs sent on the
   visited link and it should not send RAs on the visited link.

   When the MR is at home, it doesn't normally use any information
   received from RAs sent by a neighbouring router, i.e. the BR.  It
   has a link-local address and if it has a larger scope address
   configured on an interface, then that is normally done manually.
   Actually, routers are usually prohibited from using information
   received in RAs more than for logging and synchronization purposes.
   When the MR is in a foreign network, it needs a way to configure a
   Care-of Address.  In the hosts case this is done by stateless or

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   stateful autoconf.  In the MR case, the stateful is possible, while
   the stateless is normally prohibited.  A good way for address
   autococnfiguration for the MR should be identified, be it DHCP, or
   modified RAs, or modified router's behaviour to accept RAs.

   Assume the MR is at home and a non-link-local (site- or global)
   home address is configured on the interface connecting to the home
   link (supposedly the same interface that will change CoAqs when
   visiting).  The MR-at-home will do periodic NAs for this home
   address; this behaviour should stop when MR is visiting.  This
   modified behaviour is already taken into consideration by Mobile
   IPv6 MN.  In the particular MR case, most ND operations of MR are
   delegated to the HA, and such most entries of Neighbour Cache,
   Destination Cache that are related to the home link will disappear.
   New entries that are relevant in the foreign network will populate
   those tables.  When coming back home, all ND entries should be
   replaced back with the entries related to the home network.

   Another specific case in point is the default route.  As already
   presented with the router behaviour with respect to RAs, a default
   route is not normally configured by MR from a received RA.  When
   the MR is in a foreign network, it should have a default route that
   points to its BR (but through the MRHA tunnel) and another
   non-tunnelled default route towards the current AR.  Moreover, all
   MR's routing table entries that pointed to BR when the MR was at
   home, should still continue to point to BR (through the MRHA
   tunnel).  The same is true for all routing table entries of the BR.

7.6 Separation of routing and mobility for MR

   The necessity of the separation between mobility vs. routing
   exchanges holds true irrespective to whether dynamic or static
   routing is used.  If static routing is used, then BR has routes
   towards the mobile network through the MR, and MR has routes
   towards the Internet through the BR.  If dynamic routing is used,
   then the MR and BR dynamically exchange routing information that is
   manually configured in the routing configuration files of MR and of
   BR, as well as routing information that is delivered by other
   routers external to the home network (be it beyond the BR or beyond
   the MR).  The entities concerned with routing in the home network
   are only BR and MR.  This behaviour should continue when network
   mobility is introduced, presumably by deploying an HA (but not
   touching the BR).  MR and HA should exchange only the information
   related to mobility but not the information related to routing.

7.7 Router Renumbering

   Router Renumbering for IPv6 [7] is a technique where routers of a
   home network are instructed to change the prefixes they advertise.
   In the context here, it should be possible for the MR to be
   re-numbered when it is at home as well as when it is visiting.

   The renumbering mechanisms provided by Mobile IPv6 (mobile prefix
   solicitations and advertisements) are not relevant for changing the
   prefixes advertised by the MR towards the mobile network; but these

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   mechanisms should still be used for MR when MR is acting as an MH.
   In order for router renumbering to work for MR when acting as MR,
   the MR should at least be able to maintain its multicast
   subscription to all-routers group valid at home.

8. Mobile Router behaviour

   The MR-HA tunnel is an IP-in-IP tunnel maintained by MR and HA.
   This is not a "tunnel" in the sense referred to sometimes by
   employing the IPv6 routing headers.

   The behaviour of the Mobile Router is the behaviour of a normal
   router with the main exception of the order of search in relevant
   routing tables, with the addition of a step to search in the MRHA
   tunnel table.  The exact search steps will be detailed later.
   Various implementations do it in various ways.

   A generic behaviour of a router forwarding a packet having
   destination d, or the behaviour of MR when it is at home:
   -determine the packet is for itself or not, by comparing d to all
    addresses assigned to all interfaces.
   -if not for itself then search the routing table for a prefix that
    matches d under a prefix.  Pick d2.
   -search the destination cache for an exact match for d2.  If found,
    then send the packet to the L2 address in the DC entry.  If not
    found, then create it by doing the ND exchange; then send it to
    what ND found.

   From that behaviour, here is the modified mobile router behaviour:
   -determine the packet is for itself or not, by comparing d to all
    addresses assigned to all interfaces.
   -if not for itself then search the routing table for a prefix that
    matches d under a prefix.  Pick d2.
   +determine whether this entry in the routing table has a
    corresponding entry in the MRHA tunnel table.  If yes, then
    encapsulate towards the HA marked there and create a new packet,
    with source s CoA and new destination d from the tunnel table
    (Home Agent address).
   -search the destination cache for an exact match for d2, and that
    is not linked to the tunnel table.  If found, then send the packet
    to the L2 address in the DC entry.  If not found, then create it
    by doing the ND game; then send it to what ND found.

8.1 CoA Configuration

   This can be done by configuring an address based on a prefix
   received from the AR.  However, routers don't take into account
   RAs, normally.  It can be solved by saying that in this case MR is
   not quite a router but more of a host.

   It can also be done by means of DHCPv6 messaging, where there is no
   distinction between hosts and routers.

8.2 Discovering HA
   Do it as a Mobile IPv6 MH, except that.  Anycast.

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8.3 Sending BUs to HA

   Do the normal Mobile IPv6 signalling with its Home Agent.  The BUs
   sent contain a distinguishing bit 'R'.

8.4 Search order in various tables

   Further complicating the mobile routing issues, the Destination
   Cache is being specified with the option of being capable of being
   fusioned with the Routing Table.  The same stands for the Binding
   Cache.  It is then possible to have the DC, the BC and the routing
   table as a unique and only large routing table.  With this kinds of
   unknowns, it is difficult for the authors, at present time, to
   specify a proper search order in the respective structures, even if
   we feel this is truly important.  Or probably the behaviour of a MR
   and HA can be specified without going into the details of these
   structures, leaving implementations freedom of choice.

9. Home Agent behaviour

   The MR-HA tunnel is an IP-in-IP encapsulation tunnel [20]
   maintained by MR and HA.  This is not a "tunnel" in the sense
   referred to sometimes by employing the IPv6 routing headers.

   The behaviour of the Home Agent is the behaviour of a normal Mobile
   IPv6 HA with the main exception of the order of search in relevant
   routing tables, with the addition of a step to search in the MRHA
   tunnel table.  The exact search steps will be detailed.

   The Home Agent uses proxy-ND to defend the link-local address of
   the MR when the MR is not at home.  When the MR is at home, the HA
   stops defending MR's link-local address.

   When the MR is not at home, the L2 address of the link-local
   address of the MR is requested by neighbouring routers (such as BR)
   or by FNs that have entries in their routing tables or destination
   caches through MR's link-local address.  HA should reply to these
   requests with its own L2 address and as such receive all packets
   that have dst address containing any address of all hosts and
   routers in the mobile network.  Following this, the HA will search
   its BC as well as its routing table, then it will encapsulate those
   packets through the MRHA tunnel and sent according to the normal
   HA's destination cache and routing tables, towards the current
   Care-of Address of the Mobile Router.

   When HA is a host, HA doesn't need to have a routing table
   containing entries towards MR or hosts and routers behind MR.  When
   HA is a host, HA's routing table should contain only entries
   related to the neighbouring fixed routers.  For example HA has a
   default route towards BR.

10. Route Optimization

   Route Optimization problem description is elsewhere.


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   RO is an absolutely necessary need for mobile networks for Mobile
   IPv6.

   It might very well be that the need for RO might bring with it the
   need to put prefixes in the BUs towards CN.

   The previous scenarios allow for nested mobile networks as well.
   But the functioning suffers of drawbacks.

   The MRHA-enhanced Mobile IPv6 scenarios described previously suffer
   from important drawbacks, such as multiple nested tunnels, lack of
   route optimization with the CN.

   An example of an important inconvenient of using exclusively
   vanilla Mobile IPv6 with MRHA is when nesting: consider two mobile
   networks, each MR having its own HA in different domains.  The
   first MR attaches to an AR and the second MR attaches under the
   first mobile network.  In this case, two LFNs situated one on the
   first net and the second on the second net are capable to
   communicate with each other, but communication goes through both
   first MR's HA and through second's.  In practice this exposes a
   paradox where if first MR loses connection to AR, then even if the
   two nets stay attached, the two LFNs can not communicate.

11. Security Considerations

   Security threat analysis of Mobile IPv6 when a Mobile Router is
   used instead of a Mobile Host.  Not a threat analysis of RO.

   The threat analysis of Mobile IPv6 for hosts is presented in [10].
   When router moves instead of host, new threats appear.

   When MR at home and using secured RIP [3] or OSPF [18] (whose IPv6
   version [5] employs IPsec), then that level of security must be
   maintained when MR is away from home.

11.1 Security of the MRHA tunnel

   The MRHA tunnel is protected as required by the Mobile IPv6
   specification for the MNHA tunnel [2].

   MR and HA maintain a security association, share the same key.

11.2 Security for Route Optimization

   Since RO is not treated in this document, then the return
   routability tests for MR are not described.

   MR could do CoTI for MR's CoA and HoTI for LFN's address.  In that
   case LFN's address must be bound to MR, presumably by delegation
   mechanisms.

   MR if acting as an MN must do HoTI/CoTI for itself, if that MN
   needs RO.  If MR acting as MN, then its LFNs must not take


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   advantage of the results of having an SA MN-CN.  Or if they do,
   then MR must have some form of delegation support.

Acknowledgements

   Some of the issues presented in this document have not yet been
   discussed publicly, as far as the authors are aware, except for the
   places where specific references to prior drafts is explicitely
   made.  Some of the issues have been discussed on the nemo mailing
   list, and proper acknowledgment will be given here.  This document
   being submitted for public review, all comments are welcome and
   contributors will be properly acknowledged.

Changes

   October 2002: revision 00 submitted.

References

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

   [2]  Arkko, Jari, Devarapalli, Vijay, and Dupont, Francis, "Using
        IPsec to Protect Mobile IPv6 Signaling between Mobile Nodes
        and Home Agents", draft-ietf-mobileip-mipv6-ha-ipsec-01.txt,
        IETF Internet Draft, October 2002. (Work in Progress).

   [3]  Baker, F. and Atkinson, R., "RIP-2 MD5 Authentication", RFC
        2082, January 1997.

   [4]  Cisco authors, "Cisco Mobile Networks", whitepaper browsed
        October 25, 2002 at
        http://www.cisco.com/univercd/cc/td/doc/product/software/
        ios122/122newft/122t/122t4/ftmbrout.pdf

   [5]  Coltun, R., Ferguson, D. and Moy, J., "OSPF for IPv6", RFC
        2740, December 1999.

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

   [7]  Crawford, M., "Router Renumbering for IPv6", RFC 2894, August
        2000.

   [8]  Ernst, Thierry, Olivereau, Alexis, Bellier, Ludovic,
        Castelluccia, Claude and Lach, Hong-Yon, "Mobile Networks
        Support in Mobile IPv6",
        draft-ernst-mobileip-v6-network-03.txt, IETF Internet Draft,
        March 2002. (Work in Progress).

   [9]  Ernst, Thierry and Lach, Hong-Yon, "Network Mobility Support
        Terminology", draft-ernst-nemo-terminology-00.txt, IETF
        Internet Draft, October 2002. (Work in Progress).



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INTERNET-DRAFT        Mobile Networks with MRHA            October 2002

   [10] Harkins, D., Mankin, A., Narten, T., Nikander, P., Nordmark,
        E., Patil, B. and Roberts, P., "Threat Models introduced by
        Mobile IPv6 and Requirements for Security",
        draft-ietf-mobileip-mipv6-scrty-reqts-02.txt, IETF Internet
        Draft, November 2001. (Work in Progress).

   [11] Hedrick, C., "Routing Information Protocol", RFC 1058, June
        1998.

   [12] Johnson, David B., Perkins, Charles E. and Arkko, Jari,
        "Mobility Support in IPv6", draft-ietf-mobileip-ipv6-18.txt,
        IETF Internet Draft, June 2002. (Work in Progress).

   [13] Kniveton, Timothy J., Malinen, Jari T. and Devarapalli, Vijay,
        "Mobile Router Support with Mobile IP",
        draft-kniveton-mobrtr-02.txt, IETF Internet Draft, July
        2002. (Work in Progress).

   [14] Leung, K. and Shell, D. and Ivancic, W. D. and Stewart,
        D. H. and Bell, T. L. and Kachmar, B. A., "Application of
        Mobile-IP to Space and Aeronautical Networks", IEEE Proceedngs
        of the Aerospace Conference, 2001.

   [15] Malkin, G., "RIP Version 2, Carrying Additional Information",
        RFC 1723, November 1994.

   [16] Malkin, G., "RIPng for IPv6", RFC 2080, January 1997.

   [17] Montenegro, G., ed., "Reverse Tunneling for Mobile IP,
        revised", RFC 3024, January 2001.

   [18] Moy, J., "OSPF Version 2", RFC 2328, April 1998.

   [19] Narten, T., Nordmark, E. and Simpson, W., "Neighbour Discovery
        for IP Version 6 (IPv6)", RFC 2461, December 1998.

   [20] Perkins, C., "IP Encapsulation within IP", RFC 2003, October
        1996.

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















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Authors' Addresses

  Alexandru Petrescu                  Miguel Catalina-Gallego
  Motorola Labs                       Motorola Labs
  Espace Technologique de St Aubin    Espace Technologique de St Aubin
  Gif-sur-Yvette 91193                Gif-sur-Yvette 91193
  France                              France
  Phone:  +33 1 69354827              Phone:  +33 1 69352541
  Alexandru.Petrescu@motorola.com     Miguel.Catalina@motorola.com

  Christophe Janneteau                Hong-Yon Lach
  Motorola Labs                       Motorola Labs
  Espace Technologique de St Aubin    Espace Technologique de St Aubin
  Gif-sur-Yvette 91193                Gif-sur-Yvette 91193
  France                              France
  Phone:  +33 1 69352548              Phone:  +33 1 69352536
  Christophe.Janneteau@motorola.com   Hong-Yon.Lach@motorola.com

  Alexis Olivereau
  Motorola Labs
  Espace Technologique de St Aubin
  Gif-sur-Yvette 91193
  France
  Phone:  +33 1 69352516
  Alexis@motorola.com































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