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Versions: 00 draft-ietf-mip6-nemo-v4traversal

Personal                                                     H. Soliman
                                                            G. Tsirtsis
                                                                Flarion
Internet Draft
Document: draft-soliman-v4v6-mipv6-00.txt

Category: Standards Track                                   March 2004
Expires: September 2004


                          Dual Stack Mobile IPv6
                      draft-soliman-v4v6-mipv6-00.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
   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 specification adds IPv4 extensions to Mobile IPv6 to allow dual
   stack mobile nodes to roam within the Internet using Mobile IPv6
   only while simultaneously maintaining connections using their IPv4
   and IPv6 home addresses.















<Soliman and Tsirtsis>            1
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   Table of Contents

1. Introduction.......................................................2
1.1 Why Mobile IPv6 only?.............................................2
2. Solution overview..................................................3
2.1. Dynamic Home Agent Address Discovery.............................3
2.2. Binding management...............................................4
2.2.1 Visited network supports IPv6...................................4
2.2.2 Visited network supports IPv4 only (public addresses)...........5
2.3. Route optimization...............................................5
2.4. Dynamic IPv4 home address allocation.............................6
3. Extensions and modifications to Mobile IPv6........................6
3.1. Binding update extensions........................................6
3.1.1 IPv4 home address option........................................6
3.2. Binding acknowledgement extensions...............................6
3.2.1 IPv4 address acknowledgement option.............................7
3.3. Mobile node operation............................................7
3.4. Home agent operations............................................9
3.5. Correspondent node operations...................................10
4. Security considerations...........................................10
5. References........................................................10
Author's Addresses...................................................11



1. Introduction

   Mobile IPv6 allows mobile nodes to move within the Internet while
   maintaining reachability and ongoing sessions, using an IPv6 home
   address. However, since IPv6 is not widely deployed, it is unlikely
   that mobile nodes will use IPv6 addresses only for their
   connections. It is reasonable to assume that mobile nodes will, for
   a long time, need an IPv4 home address that can be used by upper
   layers. The current Mobile IPv6 specification does not allow mobile
   nodes to use an IPv4 home address. Hence, this specification extends
   Mobile IPv6 capabilities to allow dual stack mobile nodes to request
   that their home agent (also dual stacked) tunnel IPv4/IPv6 packets
   addressed to their home addresses, to their IPv4/IPv6 care-of
   address(es).

   As a result, mobile nodes only need Mobile IPv6 to manage mobility
   while moving within the Internet. This specification provides the
   extensions needed in order to allow Mobile IPv6 only to be used by
   dual sack mobile nodes.

1.1 Why Mobile IPv6 only?

   IPv6 offers a number of improvements over today’s IPv4, primarily
   due to its large address space. Mobile IPv6 offers a number of
   improvements over Mobile IPv4, mainly due to capabilities inherited
   from IPv6. For instance, route optimization and Dynamic home agent
   discovery can only be achieved with Mobile IPv6.


<Soliman and Tsirtsis>                                               2
                       <Dual Stack Mobile IPv6>        <August> <2003>


   One of the advantages of the large address space provided by IPv6 is
   that it allows mobile nodes to obtain a global care-of address
   wherever they are. Hence, there is no need for NAT traversal
   techniques designed for Mobile IPv4. This allows Mobile IPv6 to be a
   significantly simpler and more bandwidth efficient mobility
   management protocol.

   All of the above benefits make the case for using Mobile IPv6 only
   for dual stack mobile nodes.

2. Solution overview

   In order to allow Mobile IPv6 to be used by dual stack mobile nodes,
   the following needs to be done:

   - Mobile nodes should be able to use an IPv4 and IPv6 home or care-
   of address simultaneously and update their home agents accordingly.

   - Mobile nodes need to be able to know the IPv4 address of the home
   agent as well as its IPv6 address. There is no need for IPv4 prefix
   discovery however.

   This section presents an overview of the extensions required in
   order to allow mobile nodes to use Mobile IPv6 only for IP mobility
   management.

2.1. Dynamic Home Agent Address Discovery

   Mobile IPv6 allows mobile nodes to discover their home agents by
   appending a well-known anycast interface identifier to their home
   link’s prefix. The mobile node sends a Mobile Prefix solicitation
   and receives a Mobile Prefix Advertisement containing all prefixes
   advertised on the home link.

   To allow mobile nodes to use an IPv4 home address they need to be
   configured with the home agent’s IPv4 address and possibly with the
   IPv4 home address. A dual stack mobile node MAY send a Mobile Prefix
   Solicitation message encapsulated in IPv4 (i.e. IPv6 in IPv4) in the
   case where the mobile node has no access to IPv6 within the local
   network. Securing such messages would require the mobile node to
   have security association with the home agent, using IPsec (AH or
   ESP) and based on the mobile node’s IPv4 care-of address. However,
   since the mobile node needs to encapsulate all IPv6 traffic into
   IPv4, while located in an IPv4-only visited network, such SA would
   affect all packets. That is, the SA selectors being the protocol
   number (protocol is always IP in IP), as well as, source and
   destination addresses are all common to all packets. Therefore, it
   is RECOMMENDED that the mobile node does not use Dynamic Home Agent
   Address Discovery when located in an IPv4-only network.

   From the above discussion, it is clear that the mobile node will
   need to be configured with its home agent addresses (IPv4 and IPv6)
   and its home addresses.

<Soliman and Tsirtsis>                                               3
                       <Dual Stack Mobile IPv6>        <August> <2003>



2.2. Binding management

   A dual stack mobile node will need to update its home agent with its
   care-of address. If a mobile node has an IPv4 and an IPv6 home
   address it will need to create a binding cache entry for each
   address. The format of the IP packet carrying the binding update and
   acknowledgement messages will vary depending on whether the mobile
   node has access to IPv6 in the visited network. There are three
   different scenarios to consider with respect to the visited network:

   A. The visited network has IPv6 connectivity and provides the mobile
      node with a care-of address (in a stateful or stateless manner),
      in addition to IPv4 addresses (public or private).

   B. The mobile node can only configure a globally unique IPv4 address
      in the visited network.
   C. The mobile node can only configure a private IPv4 address in the
      visited network.

   This specification is only concerned with cases A and B. Case C is
   not supported by this specification. Case C can be supported if the
   visited network provided IPv6 service, e.g. by introducing an ISATAP
   router that provides global IPv6 connectivity. Binding management in
   cases A and B is considered in the following sections.

2.2.1 Visited network supports IPv6

   In this case, the mobile node is able to configure a globally unique
   IPv6 address. The mobile node will send a binding update to the IPv6
   address of its home agent, as defined in [1]. The binding update
   will include the IPv4 home address option introduced in this
   document. After receiving the binding update, the home agent creates
   two binding cache entries, one for the mobile node’s IPv4 home
   address, and another for the mobile node’s IPv6 home address. Both
   entries will point to the mobile node’s IPv6 care-of address. Hence,
   whenever a packet is addressed to the mobile node’s IPv4 or IPv6
   home addresses, it will be tunneled in IPv6 to the mobile node’s
   IPv6 care-of address included in the binding update. Effectively,
   the mobile node establishes two different tunnels, one for its IPv4
   traffic (IPv4 in IPv6) and one for its IPv6 traffic (IPv6 in IPv6)
   with a single binding update. The security implications of this
   mechanism are discussed in the security considerations section.

   In this scenario, the only addition to [MIPv6] is the inclusion of
   the IPv4 home address option in the binding update message.

   After accepting the binding update and creating the corresponding
   binding cache entries, the home agent MUST send a binding
   acknowledgement to the mobile node as defined in [MIPv6]. In
   addition, if the binding update included an IPv4 home address
   option, the binding acknowledgement MUST include the IPv4 address
   acknowledgment option as described later in this specification. This

<Soliman and Tsirtsis>                                               4
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   option informs the mobile node whether the binding was accepted for
   the IPv4 home address. If this option is not included in the binding
   acknowledgement and the IPv4 home address option was included in the
   binding update, the mobile node MUST assume that the home agent does
   not support the IPv4 home address option and therefore SHOULD NOT
   include the option in future binding updates to that home agent
   address.

   The routing header in the binding update MUST include the mobile
   node’s IPv6 home address as specified in [MIPv6].

2.2.2 Visited network supports IPv4 only (public addresses)

   In this scenario the mobile node will need to tunnel IPv6 packets
   containing the binding update to the home agent’s IPv4 address. The
   mobile node uses the IPv4 address it gets from the visited network
   as a source address in the outer header. The binding update will
   contain the mobile node’s IPv6 home address in the home address
   option. However, since the care-of address in this scenario is the
   mobile node’s IPv4 address, the mobile node MUST include its IPv4
   care-of address in the IPv6 packet. The IPv4 address is represented
   in an IPv4-mapped IPv6 address and is included in the source address
   field of the IPv6 header.

   If the mobile node had an IPv4 home address, it MUST also include
   the IPv4 home address option described in this specification.

   After accepting the binding update, the home agent MUST create a new
   binding cache entry for the mobile node’s IPv6 home address. If an
   IPv4 home address option were included, the home agent MUST create
   another entry for that address. All entries MUST point to the mobile
   node’s IPv4 care-of address. Hence, all packets addressed to the
   mobile node’s home address(es) (IPv4 or IPv6) will be encapsulated
   in an IPv4 header that includes the home agent’s IPv4 address in the
   source address field and the mobile node’s IPv4 care-of address in
   the destination address field.

   After accepting the binding updates and creating the corresponding
   entries, the home agent MUST send a binding acknowledgement as
   specified in [MIPv6]. In addition, if the binding update included an
   IPv4 home address option, the binding acknowledgement MUST include
   the IPv4 address acknowledgment option as described later in this
   specification. The binding update is encapsulated to the IPv4 care-
   of address (represented as an IPv4-mapped IPv6 address in the
   binding update).

2.3. Route optimization

   Route optimization, as specified in [MIPv6] will operate in an
   identical manner for dual stack mobile nodes when they are located
   in a visited network that provides IPv6 addresses to the mobile
   node. However, when located in an IPv4-only network, route


<Soliman and Tsirtsis>                                               5
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   optimization will not be possible. Therefore, mobile nodes will need
   to communicate through the home agent.

   Route optimization will not be possible for IPv4 traffic. That is,
   traffic addressed to the mobile node’s IPv4 home address. This is
   similar to using Mobile IPv4, therefore there is no reduction of
   features resulting from using this specification.

2.4. Dynamic IPv4 home address allocation

   It is possible to allow for the mobile node’s IPv4 home address to
   be allocated dynamically. This is done by including 0.0.0.0 in the
   IPv4 home address option included in the binding update. The home
   agent SHOULD allocate an IPv4 address to the mobile node and include
   it in the IPv4 address acknowledgement option sent to the mobile
   node. In this case, the lifetime of the binding is bound to the
   minimum of the lifetimes of the IPv6 binding and the lease time of
   the IPv4 home address.

3. Extensions and modifications to Mobile IPv6

   This section highlights the protocol and implementation additions
   required to support this specification.

3.1. Binding update extensions

3.1.1 IPv4 home address option

   This option is included in the Mobility Header including the binding
   update message sent from the mobile node to a home agent or Mobility
   Anchor Point.


       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
                                      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                      |     Type      |    Length     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     IPv4 home address                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type                 TBD
   Length               1
   IPv4 home address    The mobile node’s IPv4 home address that should
                        be defended by the home agent. This field could
                        contain any unicast IPv4 address (public or
                        private) that was assigned to the mobile node.
                        The value 0.0.0.0 is used to request an IPv4
                        home address from the home agent.

3.2. Binding acknowledgement extensions


<Soliman and Tsirtsis>                                               6
                       <Dual Stack Mobile IPv6>        <August> <2003>


3.2.1 IPv4 address acknowledgement option

   This option is included in the Mobility Header including the binding
   acknowledgement message sent from the home agent or Mobility Anchor
   Point to the mobile node. This option indicates whether a binding
   cache entry was created for the mobile node’s IPv4 address.
   Additionally, this option can include an IPv4 home address in case
   the mobile node was not configured with one (i.e. if the unspecified
   IPv4 address was included in the binding update).

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |    Length     |   Status      |Reserved       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      IPv4 home address                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type                 TBD

   Length               1

   Status               Indicates success or failure for the IPv4 home
                        address binding. Values from 0 to 127 indicate
                        success. Higher values indicate failure. The
                        following values are reserved:
                                0   Success
                                128 Failure, reason unspecified
                                129 Administratively prohibited
                                130 Incorrect IPv4 home address
                                131 Invalid IPv4 address
                                132 Dynamic IPv4 home address
                                    assignment not available

   IPv4 home address    The IPv4 home address that the home agent will
                        use in the binding cache entry. This could be a
                        public or private address. This field MUST
                        always contain the mobile node’s IPv4 address.
                        If the address were dynamically allocated the
                        home agent will add the address to inform the
                        mobile node. Otherwise, if the address were
                        statically allocated to the mobile node, the
                        home agent will copy it from the binding update
                        message.

3.3. Mobile node operation

   In addition to the operations specified in [MIPv6], this
   specification requires mobile nodes to be able to support an IPv4
   home address. The IPv4 home address is never sent in the IPv4-mapped
   IPv6 address format. This is primarily done to save bandwidth.
   However, to simplify the mobile node’s implementation, they SHOULD
   store the IPv4 home address in the binding update list, using the

<Soliman and Tsirtsis>                                               7
                       <Dual Stack Mobile IPv6>        <August> <2003>


   IPv4-mapped IPv6 format. Mobile nodes are also required to be
   configured with the home agent’s global IPv4 address.

   When sending an IPv6 packet containing a binding update while
   connected to an IPv4-only access network, mobile nodes MUST ensure
   the following:

   - The IPv6 packet is encapsulated in an IPv4 packet
   - The source address in the IPv4 header is the mobile node’s IPv4
     care-of address
   - The destination address in the IPv4 header is the home agent’s
     IPv4 address.
   - The source address in the IPv6 header is the mobile node’s IPv4-
     mapped IPv6 address. That is, the same IPv4 address in the outer
     header is placed in the IPv6 header using the mapped address
     format.
   - The home address option contains the IPv6 home address as
     specified in [MIPv6].
   - The IPv4 home address option MAY be included in the mobility
     header. This option contains the IPv4 home address. If the mobile
     node did not have a static home address it MAY include the
     unspecified IPv4 address, which acts as a request for a dynamic
     IPv4 home address.
   - The IPv6 packet MUST be authenticated as per [MIPv6], based on the
     mobile node’s IPv6 home address.

   When sending a binding update from a visited network that supports
   IPv6, the mobile node MUST follow the rules specified in [MIPv6]. In
   addition, if the mobile node has an IPv4 home address or needs one,
   it should include the IPv4 home address option in the mobility
   header. If the mobile node already has a static IPv4 home address,
   such address MUST be included in the IPv4 home address option.
   Otherwise, if the mobile node needs a dynamic IPv4 address, it
   should include the IPv4 unspecified address in the IPv4 home address
   option.

   When the mobile node receives a binding acknowledgement from the
   home agent, it should follow the rules in [MIPv6]. In addition, the
   following actions MUST be made:

   - If the mobility header includes and IPv4 address acknowledgement
     option indicating success, the mobile node should create two
     entries in its binding update list, one for the IPv6 home address
     and another for the IPv4 home address.
   - If no IPv4 address acknowledgement option were present, and an
     IPv4 home address option was present in the binding update, the
     mobile node MUST only create one binding update list entry for its
     IPv6 home address. The mobile node MAY include the IPv4 home
     address option in future binding updates.
   - If an IPv4 address acknowledgement option were present and it
     indicates failure for the IPv4 home address binding, the mobile
     node MUST NOT create an entry for that address in its binding
     update list. The mobile node MAY include the IPv4 home address

<Soliman and Tsirtsis>                                               8
                       <Dual Stack Mobile IPv6>        <August> <2003>


     option in future binding updates.

   Note that a mobile node complying with this specification MUST
   configure an IPv4-mapped IPv6 address on its interface in the
   visited network. This is needed in order to allow the mobile node to
   receive binding acknowledgements from its home agent while located
   in an IPv4-only network.

3.4. Home agent operations

   In addition to the home agent specification in [MIPv6], the home
   agent needs to be able to process the IPv4 home address option and
   generate the IPv4 address acknowledgement option. Both options are
   included in the mobility header.

   In order to comply with this specification, the home agent MUST be
   able to find the IPv4 home address of a mobile node when given the
   IPv6 home address. That is, given an IPv6 home address, the home
   agent MUST store the corresponding IPv4 home address if a static one
   is present. If a dynamic address were requested by the mobile node,
   the home agent MUST store that address (associated with the IPv6
   home address) after it’s allocated to the mobile node.

   When the home agent receives a binding update containing the IPv4
   home address option, it needs to follow all the steps in [MIPv6], in
   addition, the following checks MUST be done:

   - If the IPv4 home address option contains a valid unicast IPv4
     address, the home agent MUST check that this address is allocated
     to the mobile node that has the IPv6 home address included in the
     home address option.

   - If the IPv4 home address option contained the unspecified IPv4
     address, the home agent SHOULD dynamically allocate and IPv4 home
     address to the mobile node. If none is available, the home agent
     MUST return an appropriate error code in the status field of the
     IPv4 address acknowledgement option.

   - If the binding update is accepted for the IPv4 home address, the
     home agent MUST create a binding cache entry for the IPv4 home
     address. The IPv4 home address MAY be stored in the IPv4-mapped
     IPv6 address format. The home agent MUST include an IPv4
     acknowledgement option in the mobility header containing the
     binding acknowledgement.

   If the binding update is accepted for both IPv4 and IPv6 home
   addresses, the home agent MUST create two separate binding cache
   entries, on for each home address. The care-of address is the one
   included in the binding update. If the care-of address is an IPv4-
   mapped IPv6 address, the home agent MUST setup a tunnel to the IPv4
   care-of address of the mobile node.



<Soliman and Tsirtsis>                                               9
                       <Dual Stack Mobile IPv6>        <August> <2003>


   When sending a binding acknowledgement to the mobile node, the home
   agent would construct the message according to [MIPv6]. Note that
   the routing header MUST always contain the IPv6 home address as
   specified in [MIPv6].

   If the care-of address of the mobile node were an IPv4 address, the
   home agent MUST include this address in the destination address in
   the IPv6 header using the IPv4-mapped IPv6 format. The home agent
   MUST then encapsulate the packet in an IPv4 header. The source
   address is set to the home agent’s IPv4 address and the destination
   address is set to the mobile node’s IPv4 care-of address.

   After creating a binding cache entry for the mobile node’s home
   addresses. All packets sent to the mobile node’s home addresses are
   tunneled by the home agent to the mobile node’s care-of address. If
   the care-of address is an IPv4 address, packets are encapsulated in
   an IPv4 header. Note that the mapped address format is not used to
   encapsulate the mobile node’s traffic. The mapped address format is
   only used when sending binding acknowledgements to the mobile node.

3.5. Correspondent node operations

   The specification has no impact on IPv4 or IPv6 correspondent nodes.

4. Security considerations

   This specification allows a mobile node to send one binding update
   for its IPv6 and its IPv4 home address. This is a slight deviation
   from [MIPv6] which requires one binding update per home address.
   However, like [MIPv6], the IPsec security association needed to
   authenticate the binding update is till based on the mobile node’s
   IPv6 home address. Therefore, in order to authenticate the mobile
   node’s IPv4 home address binding, the home agent MUST store the IPv4
   address corresponding to the IPv6 address that is allocated to a
   mobile node. Therefore, it is sufficient for the home agent to know
   that the IPsec verification for the packet containing the binding
   update was valid provided that it knows which IPv4 home address is
   associated with which IPv6 home address. Hence, the security of the
   IPv4 home address binding is the same as the IPv6 binding.

   In effect, associating the mobile node’s IPv4 home address with its
   IPv6 home address moves the authorization of the binding update for
   the IPv4 address to the Mobile IPv6 implementation, which infers it
   from the fact that mobile node has an IPv6 home address and the
   right credentials for sending an authentic binding update for such
   address.

5. References

   [IPv6] S. Deering and B. Hinden, “Internet Protocol version 6 (IPv6)
          specification”, RFC 2460

   [KEYWORDS]   Bradner, S., "Key words for use in RFCs to Indicate

<Soliman and Tsirtsis>                                              10
                       <Dual Stack Mobile IPv6>        <August> <2003>


                Requirement Levels", BCP 14, RFC 2119, March 1997.

   [MIPv4] C. Perkins, "Mobility Support for IPv4", RFC3344

   [MIPv6] D. Johnson, C. Perkins and J. Arkko, "Mobility Support in
           IPv6", draft-ietf-mobileip-ipv6-24.txt, June 2003.

Author's Addresses

   Hesham Soliman
   Flarion Technologies
   Phone:  +61400500321
   E-mail: H.Soliman@Flarion.com

   George Tsirtsis
   Flarion Technologies
   Phone: +44-20-88260073
   Email1: G.Tsirtsis@Flarion.com
   Email2: tsirtsisg@yahoo.com



































<Soliman and Tsirtsis>                                              11


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