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Versions: 00 01 02 03 04 05 06 07 08 09 10 RFC 5454

Network Working Group                                        G. Tsirtsis
Internet-Draft                                                   V. Park
Intended status: Standards Track                                Qualcomm
Expires: April 5, 2008                                        H. Soliman
                                                    Elevate Technologies
                                                         October 3, 2007


                         Dual Stack Mobile IPv4
                     draft-ietf-mip4-dsmipv4-05.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
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   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on April 5, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2007).












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Abstract

   This specification provides IPv6 extensions to the Mobile IPv4
   protocol.  The extensions allow a dual stack node to use IPv4 and
   IPv6 home addresses as well as to move between IPv4 and dual stack
   network infrastructures.


Table of Contents

   1.  Requirements notation  . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Goals  . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.2.  Non-Goals  . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.3.  Implicit and Explicit Modes  . . . . . . . . . . . . . . .  5
   3.  Extension Formats  . . . . . . . . . . . . . . . . . . . . . .  6
     3.1.  IPv6 Prefix Extension  . . . . . . . . . . . . . . . . . .  6
     3.2.  IPv6 Code Extension  . . . . . . . . . . . . . . . . . . .  7
     3.3.  IPv6 Tunneling Mode Extension  . . . . . . . . . . . . . .  8
   4.  Mobile IP Registrations  . . . . . . . . . . . . . . . . . . . 10
     4.1.  Registration Request . . . . . . . . . . . . . . . . . . . 10
     4.2.  Registration Reply . . . . . . . . . . . . . . . . . . . . 10
     4.3.  Home Agent Considerations  . . . . . . . . . . . . . . . . 11
       4.3.1.  IPv6 Packet Processing . . . . . . . . . . . . . . . . 12
       4.3.2.  Processing intercepted IPv6 Packets  . . . . . . . . . 12
       4.3.3.  IPv6 Multicast Membership Control  . . . . . . . . . . 14
     4.4.  Foreign Agent Considerations . . . . . . . . . . . . . . . 14
     4.5.  Mobile Node Considerations . . . . . . . . . . . . . . . . 15
     4.6.  Dynamic IPv6 Prefix allocation . . . . . . . . . . . . . . 17
       4.6.1.  Mobile IP Style Address Allocation . . . . . . . . . . 17
     4.7.  Deregistration of IPv6 Prefix  . . . . . . . . . . . . . . 18
     4.8.  Registration with a private CoA  . . . . . . . . . . . . . 18
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 19
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 20
   7.  Change history . . . . . . . . . . . . . . . . . . . . . . . . 21
     7.1.  Changes from v04 to v05  . . . . . . . . . . . . . . . . . 21
     7.2.  Changes from v03 to v04  . . . . . . . . . . . . . . . . . 21
     7.3.  Changes from v02 to v03  . . . . . . . . . . . . . . . . . 21
     7.4.  Changes from v01 to v02  . . . . . . . . . . . . . . . . . 21
     7.5.  Changes from v00 to v01  . . . . . . . . . . . . . . . . . 22
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23
   9.  Normative References . . . . . . . . . . . . . . . . . . . . . 24
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 26
   Intellectual Property and Copyright Statements . . . . . . . . . . 27







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1.  Requirements notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].














































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2.  Introduction

   Mobile IPv4 [RFC3344] allows a mobile node with an IPv4 address to
   maintain communications while moving in an IPv4 network.

   Extensions defined in this document allow a node that has IPv4 and
   IPv6 addresses [RFC2460] to maintain communications with any of its
   addresses while moving in IPv4 or dual stack networks.

   Essentially, this specification separates the Mobile IPv4 signaling
   from the IP version of the traffic it tunnels.  Mobile IPv4 with the
   present extensions remains a signaling protocol that runs over IPv4,
   and yet can set-up any combination of IPv4 and/or IPv6 over IPv4
   tunnels.

   The aim is two-fold:

      On one hand, Mobile IPv4 with the present extensions becomes a
      useful transition mechanism, allowing automated but controlled
      tunneling of IPv6 traffic over IPv4 tunnels.  Dual stack nodes in
      dual stack home networks can now roam to and from legacy IPv4
      networks, while IPv4 mobile nodes and networks can migrate to IPv6
      without changing mobility management, and without upgrading all
      network nodes to IPv6 at once.

      On the other hand, and more importantly, it allows dual stack
      mobile nodes and networks to utilize a single protocol for the
      movement of both IPv4 and IPv6 stacks in the network topology.

   Note that features like Mobile IPv6 [RFC3775] style route
   optimization will not be possible with this solution as it still
   relies on Mobile IPv4 signaling, which does not provide route
   optimization.

2.1.  Goals

   a.  The solution supports the registration of IPv6 home address(es)
       and/or prefix(s) in addition to regular IPv4 home address
       registration

   b.  The solution supports static and dynamic IPv6 home address(s)/
       prefix(s) allocations

   c.  The solution supports the above registrations with and without FA
       support






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2.2.  Non-Goals

   a.  The solution does not provide support for IPv6 care-of address
       registration

2.3.  Implicit and Explicit Modes

   As defined in NEMO [RFC3963], this specification also supports two
   modes of operation; the implicit mode and the explicit mode.

   In the implicit mode, the mobile node does not include a IPv6 Prefix
   Extensions in the Registration Request.  The home agent can use any
   mechanism (not defined in this document) to determine the IPv6
   Prefix(es) owned by the mobile node and to set up forwarding for
   these prefixes.  In this mode of operation all traffic to and from
   the IPv6 prefixes MUST be encapsulated over the IPv4 tunnel between
   the mobile node's IPv4 home address and the IPv4 address of the home
   agent, and as such it is transparent to any foreign agent in the
   path.  This IPv4 tunnel is established by mechanisms that are out of
   the scope of this document on both the mobile node and home agent
   when operating in the implicit mode.

   In the explicit mode, IPv6 address bindings are signalled explicitly.
   The mobile node includes one or more IPv6 Prefix extensions in the
   Registration Request, while the home agent returns corresponding IPv6
   code extensions to accept/reject the IPv6 bindings.

   Additionally, in the explicit mode, the mobile node (when co-located
   mode of operation is used) or the foreign agent (when present) can
   indicate whether IPv6 traffic should be tunneled to the care-of
   address of the home address of the mobile node.

   The rest of this specification is primarily defining the explicit
   mode.

















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3.  Extension Formats

   The following extensions are defined according to this specification.

3.1.  IPv6 Prefix Extension

   A new skippable extension to the Mobile IPv4 header in accordance to
   the short extension format of [RFC3344] is defined here.

   This extension contains a mobile IPv6 network prefix and its prefix
   length.

       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      |   Sub-Type    | Prefix Length |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                                                               +
      |                                                               |
      +                   Mobile IPv6 Network Prefix                  +
      |                                                               |
      +                                                               +
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 1: IPv6 Prefix Extension

   Type

      DSMIPv4 Extensions (skippable type range to be assigned by IANA)

   Length

      18

   Sub-Type

      1 (IPv6 Prefix)

   Prefix Length

      Indicates the prefix length of the prefix included in the Mobile
      IPv6 Network Prefix field

   Mobile IPv6 Network Prefix





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      A sixteen-byte field containing the Mobile IPv6 Network Prefix

3.2.  IPv6 Code Extension

   A new skippable extension to the Mobile IPv4 header in accordance to
   the short extension format of [RFC3344] is defined here.

   This extension defines a mobile IPv6 network prefix and its prefix
   length, as well as a code.

       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      |   Sub-Type    |     Code      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Prefix Length |    Reserved   |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
      |                                                               |
      +                                                               +
      |                                                               |
      +                   Mobile IPv6 Network Prefix                  +
      |                                                               |
      +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 2: IPv6 Code Extension

   Type

      DSMIPv4 Extensions (skippable type range to be assigned by IANA)

   Length

      20

   Sub-Type

      2 (IPv6 Code)

   Code

      A value indicating the result of the registration request with
      respect to the IPv6 home address registration.  See below for
      currently defined Codes.

   Prefix Length




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      Indicates the prefix length of the prefix included in the Mobile
      IPv6 Network Prefix field

   Reserved

      Set to 0 by the sender, ignored by the receiver

   Mobile IPv6 Network Prefix

      A sixteen-byte field containing the Mobile IPv6 Network Prefix

   The following values are defined for use as a Code value in the above
   extension

      0 registration accepted, IPv6 to be tunneled to HoA

      1 registration accepted, IPv6 to be tunneled to CoA

      8 registration rejected, reason unspecified

      9 registration rejected, administratively prohibited

      10 registration rejected, not home subnet

      11 registration rejected, Duplicate Address Detection failed

   Note that a registration reply that does not include an IPv6 code
   extension indicates that the home agent does not support IPv6
   extensions and thus has ignored such extensions in the registration
   request.

3.3.  IPv6 Tunneling Mode Extension

   A new skippable extension to the Mobile IPv4 header in accordance to
   the short extension format of [RFC3344] is defined here.

   By including this extension in a registration request the sender
   indicates that IPv6 traffic can be tunneled to the mobile's CoA.

   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      |    Sub-Type   |   Reserved    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 3: IPv6 Tunneling Mode Extension

   Type



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      DSMIPv4 Extensions (skippable type range to be assigned by IANA)

   Length

      2

   Sub-Type

      3 (IPv6 Tunneling Mode)

   Reserved

      Set to 0 by the sender, ignored by the receiver






































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4.  Mobile IP Registrations

4.1.  Registration Request

   A mobile node MAY include one or more IPv6 prefix extensions defined
   in this specification in a registration request.

   A mobile node MAY include exactly one IPv6 tunneling mode extension
   when it uses the co-located care-of address mode of [RFC3344].

   When IPv6 prefix and/or IPv6 tunneling mode extensions are used by
   the mobile IP client, they MUST be placed after the registration
   request header and before the mobile - home authentication extension
   so they MUST be included in the computation of any authentication
   extension.

   A foreign agent MAY include exactly one IPv6 tunneling mode
   extension, defined in this specification, in a registration request
   when a mobile node registers using the care-of address mode via the
   foreign agent.

   When the IPv6 tunneling mode extension is used by a foreign agent it
   MUST be placed after the mobile - home authentication extensions and
   before the foreign - home authentication extension so they MUST be
   included in the computation of the foreign - home authentication
   extension when one exists.

4.2.  Registration Reply

   The mechanism described in the specification depends on skippable
   extensions.  For that reason, a registration reply that does not
   include an IPv6 code extension, in response to a registration request
   that included an IPv6 prefix extension, indicates that the home agent
   does not support IPv6 extensions and has ignored the request.

   If an IPv6 code extension is included in a registration reply then,
   the extension indicates the success or failure of the IPv6 prefix
   registration.  The IPv6 code extension does not affect in any way the
   code value in the registration reply header but it is superseded by
   it.  In other words if the code field in the registration reply
   header is set to a reject code, then all IPv6 prefix extensions are
   also rejected.  If the code field in the registration reply header,
   however, is set to an accept code, then an IPv6 code extension with a
   code field set to a reject code, only rejects the binding for the
   specific IPv6 prefix indicated in the same extension.

   Note that a rejecting IPv6 code extension has the same effect with
   not including such extension at all in the sense that in both cases



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   the mobile node and foreign agent must act as if the corresponding
   IPv6 prefix extension included in the registration request was
   rejected.  Of course, the inclusion of the IPv6 code extension allows
   the home agent to indicate why a given IPv6 prefix extension was
   rejected.  Consequently, home agent implementations of this
   specification SHOULD include IPv6 code extensions in registration
   reply messages, in response to registration request messages included
   IPv6 prefix extensions.

4.3.  Home Agent Considerations

   The dual stack home agent defined in this specification is a Mobile
   IPv4 [RFC3344] Home Agent, in that it MUST operate as defined in
   MIPv4 [RFC3344].  In addition to that the following mechanism are
   defined in this specification.

   For each IPv6 prefix extension included in a valid registration
   request, a home agent that supports this specification SHOULD include
   a corresponding IPv6 code extension in the registration reply
   message.  For each accepted IPv6 prefix the home agent MUST decide
   the tunneling mode it is going to use and set the Code field of the
   IPv6 code extension to the appropriate value.  The IPv6 prefix field
   of each of the IPv6 code extensions included in the registration
   reply MUST match the IPv6 prefix field of an IPv6 prefix extensions
   included in the corresponding registration request message.

   If the IPv6 home address included in a IPv6 prefix extension is not
   an on-link IPv6 address with respect to the home agent's current
   Prefix List or a prefix it is configured to serve, the home agent
   MUST reject the IPv6 prefix extension and SHOULD return an IPv6 code
   extension with rejection code "registration rejected, not home
   subnet" in the registration reply to the mobile node.

   When the IPv6 prefix extension contains a /128 IPv6 address and
   unless this home agent already has a binding for the given IPv6
   address indicated, the home agent MUST perform Duplicate Address
   Detection [RFC4862] on the mobile node's home IPv6 link before
   returning a registration reply.  This ensures that no other node on
   the home link is using the IPv6 home address.  Duplicate address
   detection is not required when the IPv6 prefix extension contains a
   prefix.  If this Duplicate Address Detection fails for the given IPv6
   home address or an associated link local address, then the home agent
   MUST reject the IPv6 prefix extensions and SHOULD return a
   registration reply to the mobile node, in which the code field of a
   corresponding IPv6 code extension is set to "registration rejected,
   Duplicate Address Detection failed".

   When the home agent sends a successful registration reply to the



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   mobile node, with the Code field of a corresponding IPv6 code
   extension set to one of the "registration accepted" values, the home
   agent assures the mobile node that its IPv6 address(es) will be kept
   unique by the home agent for as long as the lifetime is granted for
   the binding.  It also indicates the tunneling mode used i.e.,
   tunneling to home address or care-of address, based on the value of
   the code field used in the IPv6 code extension.

   Note that for IPv6 prefixes (rather than addresses), the home agent
   does not have to perform Duplicate Address Detection.

4.3.1.  IPv6 Packet Processing

   Dual stack home agents MUST use Proxy Neighbor Discovery [RFC4861] on
   behalf of the nodes they serve.  This allows the home agent to
   receive IPv6 packets addressed to the mobile node's registered IPv6
   address(es).

   The dual stack home agent MUST act as defined in MIPv6 [RFC3775],
   Section 10.4.1. in order to intercept IPv6 packets for the mobile
   nodes it serves.

   The home agent MUST advertise reachability for the registered
   prefixes as defined in NEMO [RFC3963], section 6.3.

4.3.2.  Processing intercepted IPv6 Packets

   A dual stack home agent that supports the IPv6 extensions defined in
   this specification, MUST keep track of the following IPv6 related
   state for the mobile nodes it supports, in addition to what state is
   defined in [RFC3344].

   - Registered IPv6 prefix(es) and prefix length(s)

   - Tunneling mode for IPv6 traffic:

      - Tunnel to IPv4 HoA and accept IPv6 tunneled from IPv4 HoA

      - Tunnel to CoA and accept IPv6 tunneled from CoA

   When IPv6 traffic is encapsulated over the tunnel between the HA and
   the mobile node's care-off address, the tunneling mechanism used
   should be the same with the mechanism negotiated by the Mobile IP
   header as defined in MIPv4 [RFC3344].  In that case, when IPinIP
   encapsulation is negotiated, IPv6 is tunneled over IPv4 according
   to[RFC4213].  GRE and Minimal Encapsulation techniques also allow
   tunneling of IPv6 packets by setting the Protocol Type [RFC2784] and
   Protocol [RFC2004] fields to appropriate payload type defined for



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   IPv6 by IANA.  When, however, IPv6 traffic is encapsulated over the
   tunnel between the HA and the mobile node's home address, IPv6 is
   always tunneled over IPv4 according to [RFC4213], no matter what
   tunneling mechanism is negotiated in MIPv4 signaling.

   A home agent that supports this specification MUST be able to defend
   IPv4 and IPv6 packets destined to registered mobile nodes according
   to mechanisms described in MIPv4 [RFC3344] and MIPv6 [RFC3775]
   specifications.

   Tunneling mode selection for IPv6 traffic depends on the following
   parameters in a successful registration request:

   1) Registration request is received with one or more IPv6 prefix
   extensions.  An IPv6 tunneling mode extension is not included.

      All IPv6 packets destined to the registered IPv6 prefix(es) MUST
      be tunneled by the home agent to the registered IPv4 home address
      of the mobile.  The home agent first encapsulates the IPv6 packet
      addressed to the mobile node's IPv4 home address, and then tunnels
      this encapsulated packet to the foreign agent.  This extra level
      of encapsulation is required so that IPv6 routing remains
      transparent to a foreign agent that does not support IPv6.  When
      received by the foreign agent, the unicast encapsulated packet is
      detunneled and delivered to the mobile node in the same way as any
      other packet.  The mobile node must decapsulate the received IPv4
      packet it receives in order to recover the original IPv6 packet.
      Additionally, the home agent MUST be prepared to accept reverse
      tunneled packets from the IPv4 home address of the mobile
      encapsulating IPv6 packets sent by that mobile.

   2) Registration request is received with one or more IPv6 prefix
   extensions.  An IPv6 tunneling mode extension is included.

      All IPv6 packets destined to the registered IPv6 home address(s)
      SHOULD be tunneled by the home agent to the registered care-of
      address of the mobile node.  Additionally, the home agent SHOULD
      be prepared to accept reverse tunneled packets from the care-of
      address of the mobile encapsulating IPv6 packets sent by that
      mobile.  The home agent MAY ignore the presence of the IPv6
      tunneling mode extension and act as in case (1) above.

   Packets addressed to the mobile node's IPv6 link-local address MUST
   NOT be tunneled to the mobile node.  Instead, these packets MUST be
   discarded and the home agent SHOULD return an ICMPv6 Destination
   Unreachable, Code 3, message to the packet's Source Address (unless
   this Source Address is a multicast address).




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   The home agent SHOULD check that all IPv6 packets received from the
   mobile node over a tunnel from the home address or the care-of
   address, include a source address that falls under the registered
   IPv6 prefix(es) for that mobile node.  If the source address of a
   tunneled packet is not the registered IPv4 care-of address or the
   registered IPv4 home addresses, the packet SHOULD be dropped.  If the
   source address of the encapsulated packet does not match any of the
   registered home addresses and/or prefixes the packet SHOULD be
   dropped.

   Interception and tunneling IPv6 multicast addressed packets on the
   home network are only done if the home agent supports multicast group
   membership control messages from the mobile node as described in the
   next section.  Multicast IPv6 packets addressed to a multicast
   address with link-local scope [RFC4291], to which the mobile node is
   subscribed, MUST NOT be tunneled to the mobile node.  These packets
   SHOULD be silently discarded (after delivering to other local
   multicast recipients).  Multicast packets addressed to a multicast
   address with a scope larger than link-local, but smaller than global
   (e.g., site- local and organization-local [RFC4291], to which the
   mobile node is subscribed, SHOULD NOT be tunneled to the mobile node.
   Multicast packets addressed with a global scope, to which the mobile
   node has successfully subscribed, MUST be tunneled to the mobile
   node.

4.3.3.  IPv6 Multicast Membership Control

   IPv6 multicast membership control is provided as defined in MIPv6
   [RFC3775], Section 10.4.3.  The only clarification required for the
   purpose of this specification is that all MLD [RFC2710] or MLDv2
   [RFC3810] messages between the mobile node and the home agent MUST be
   tunneled between the mobile node and the home agent, bypassing the
   foreign agent.

4.4.  Foreign Agent Considerations

   A dual stack foreign agent that supports the IPv6 extensions defined
   in this specification MUST keep track of the following IPv6 related
   state for the mobile IP clients it supports in addition to what state
   is defined in [RFC3344].

   - IPv6 Prefix(es) and Prefix Length(s)

   - Tunneling mode for IPv6 traffic:

      - accept IPv6 encapsulated in IPv4 and reverse tunnel IPv6





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      - IPv6 is tunneled directly to the IPv4 HoA so the foreign agent
      will not provide encapsulation/decapsulation services for IPv6
      traffic for this mobile.

   When a foreign agent receives a registration request with IPv6 prefix
   extension(s) it has the following choices:

   1) Ignore the extension(s).  The registration request is forwarded as
   is to the home agent.

      The foreign agent SHOULD operate according to MIPv4 [RFC3344]

   2) Attach an IPv6 tunneling mode extension to the registration
   request sent to the home agent.

      The foreign agent MUST be prepared to decapsulate and deliver IPv6
      packets, in addition to the IPv4 packets, sent to it in the home
      agent to foreign agent tunnel for that mobile node.  The foreign
      agent MUST be prepared to receive IPv6 packets from the mobile
      node, in addition to IPv4 packets.  All IPv6 traffic MUST be
      reverse tunneled to the home agent by the foreign agent
      irrespectively from the reverse tunneling setting negotiated for
      IPv4 packets by mechanisms in [RFC3024]

   If the foreign agent sets the R flag included in the mobility agent
   advertisement [RFC3344] and a mobile node uses the co-located address
   mode of operation, the foreign agent MUST NOT include an IPv6
   tunneling mode extension in the registration request messages sent
   from that mobile node.

4.5.  Mobile Node Considerations

   A dual stack mobile node that supports the extensions described in
   this document MAY use these extensions to register its IPv6 home
   address(es) and/or prefix(es) while moving between access routers.

   The mobile node MAY include one or more IPv6 Prefix extension(s) in
   the registration request.

   In this case the mobile MUST take the following action depending on
   the extensions included in the registration reply it receives in
   response to the registration request:

   1) The registration reply does not include any IPv6 code extensions.

      The mobile node SHOULD assume that the home agent does not support
      the extensions defined in this specification.  The mobile node
      SHOULD continue to operate according to MIPv4 [RFC3344].



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   2) The registration reply includes one or more IPv6 code extensions.

      The mobile node MUST match each IPv6 code extension with one of
      the IPv6 prefix extensions earlier included in the corresponding
      registration request message.

      If a matching IPv6 code extension is not included for one or more
      of corresponding IPv6 prefix extensions included in the
      registration request message, the mobile node SHOULD assume that
      these IPv6 prefixes are rejected.

      For each matching IPv6 code extensions the mobile node MUST
      inspect the Code field.  If the field is set to a rejection code
      then the corresponding IPv6 prefix registration has been rejected.
      If the Code field is set to an acceptance code then the
      corresponding IPv6 prefix registration has been accepted.

      If the Code field is set to "0" then the mobile node MUST be
      prepared to send/receive IPv6 packets encapsulated in the
      bidirectional tunnel between the home agent address and the
      registered IPv4 home address of the mobile node.

      If the Code field is set to "1" then the mobile node MUST act as
      follows:

      - If the care-of address mode of operation is used, the mobile
      node MUST be prepared to send/receive IPv6 traffic on its
      interface natively (i.e., without any Mobile IP related tunnel
      headers).  If reverse tunneling is negotiated, then IPv6 traffic
      sent by the mobile node may be reverse tunneled via the foreign
      agent using either the direct delivery style or the encapsulating
      delivery style as defined in [RFC3024] for IPv4 traffic.

      - If the co-located care-of address mode is used, the mobile node
      MUST be prepared to send/receive IPv6 packets over the
      bidirectional tunnel between the home agent address and its co-
      located care-of address.

   The mobile node SHOULD include exactly one IPv6 tunneling mode
   extension if it uses the co-located care-of address model and it
   wants to request that IPv6 packets are tunneled to its co-located
   care-of address.  If the mobile node uses the co-located care-of
   address model but it does not include the IPv6 tunneling mode
   extension the home agent will tunnel IPv6 traffic to the mobile
   node's home address.  The mobile node MUST NOT include an IPv6
   tunneling mode extension if it uses the care-of address mode of
   operation.  Note that if the mobile includes an IPv6 tunneling mode
   extension in this case, IPv6 packets could be tunneled to the FA by



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   the HA.  The FA is then likely to drop them since it may not have
   appropriate state to process them.

4.6.  Dynamic IPv6 Prefix allocation

   The dynamic IPv6 prefix allocation described in the following section
   reuses the Mobile IPv4 mechanisms defined for IPv4 address
   allocation.  An implementation can use a different mechanism to
   dynamically allocate IPv6 addresses in which case once such IPv6
   addresses are allocated, they can be registered using the extensions
   and mechanism already described.

4.6.1.  Mobile IP Style Address Allocation

   A mobile node may include one or more IPv6 prefix extensions with the
   IPv6 prefix field set to zero.  The mobile node MAY set the prefix
   length field of such extensions to zero or to a length of its choice
   as a hint to the home agent.  Such IPv6 prefix extensions indicate
   that the mobile node requests IPv6 address(es) and prefix(es) to be
   assigned to it by the home agent.

   A home agent receiving an IPv6 prefix extension with the IPv6 prefix
   field set to zero MAY return an IPv6 code extension with the IPv6
   prefix field set to the IPv6 prefix allocated to the mobile node.
   The length of that prefix is at the discretion of the home agent.
   The home agent may take into account the prefix length hint if one is
   included in the IPv6 prefix extension.

   A mobile node MAY include one or more IPv6 prefix extensions with the
   IPv6 Prefix field set to ::interface_identifier, where
   interface_identifier is the unique layer 2 address of the client.
   The interface_identifier MUST be less than or equal to 64 bits in
   length.  In this case the prefix length field SHOULD be set to 128.

   The home agent MAY in this case return an IPv6 Code extension with:

      - the IPv6 prefix field set to PREFIX:: and the prefix length
      field set to the desired prefix length value.  In this case the
      PREFIX:: subnet is allocated to the mobile node, which should
      proceed in constructing IPv6 addresses as defined in [RFC4862]

      - the IPv6 prefix field set to PREFIX::interface_identifier and
      the prefix length field set to 128.  In this case an individual
      IPv6 address is allocated to the mobile node.







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4.7.  Deregistration of IPv6 Prefix

   The mobile IP registration lifetime included in the registration
   request header is valid for all the bindings created by the
   registration request, which may include bindings for IPv6 address(es)
   and prefix(es).

   A registration request with a zero lifetime can be used to remove all
   bindings from the home agent.

   A re-registration request with non-zero lifetime can be used to
   deregister some of the registered IPv6 prefixes by not including
   corresponding IPv6 prefix extensions in the registration request
   message.

4.8.  Registration with a private CoA

   If the care-of address is a private address then Mobile IP NAT
   Traversal as [RFC3519] MAY be used in combination with the extensions
   described in this specification.  In that case, to transport IPv6
   packets, the next header field of the Mobile Tunnel Data message
   header [RFC3519] MUST be set to the value for IPv6."





























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5.  Security Considerations

   This specification operates in the security constraints and
   requirements of [RFC3344].  It extends the operations defined in
   [RFC3344] for IPv4 home addresses to cover home IPv6 addresses
   prefixes and provides the same level of security for both IP address
   versions.

   As defined in the security considerations section of RFC3344, ingress
   filtering in the data path may prevent mobiles from using triangular
   routing for their IPv6 communications even if the foreign agent used
   supports the dual stack extensions defined in this specification.  In
   such cases reverse tunneling can be used to allow for effective
   ingress filtering in intermediate routers without blocking IPv6
   traffic to reach its destination.

   Home Agents MUST perform appropriate checks for reversed tunneled
   IPv6 packets similar to what is defined in [RFC3024] for IPv4
   packets.  The check defined in [RFC3024] requires that the outer
   header's source address is set to a registered care-of address for
   the mobile node and as such the same check protects from attacks
   whether the encapsulated (inner) header is IPv4 or IPv6.

   In addition to that, the home agent SHOULD check that the source
   address of the inner header is a register IPv4 or IPv6 home address
   for this mobile node.  If that is not the case, the home agent SHOULD
   silently discard the packet and log the event as a security
   exception.























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6.  IANA Considerations

   This specification requires the allocation of a new number for
   DSMIPv4 extensions, from the space of numbers for skippable mobility
   extensions (i.e., 128-255) defined for Mobile IPv4 [RFC3344] at
   http://www.iana.org/assignments/mobileip-numbers.

   This specification also creates a new subtype space for the type
   number of this extension.  The subtype values 1, 2 and 3 are defined
   in this specification.

   Similar to the procedures specified for Mobile IPv4 [RFC3344] number
   spaces, future allocations from this number space require expert
   review [RFC2434].





































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7.  Change history

   NOTE TO RFC EDITOR: Remove section Section 7 before publication.

7.1.  Changes from v04 to v05

   Corrected nits.

   Added IANA considerations section.

7.2.  Changes from v03 to v04

   Clarified that DAD is only needed on IPv6 addresses and not prefixes,
   in Section 4.3.

   Clarified of tunneling process in Section 4.3.2

   Numerous editorial and clarification changes.

7.3.  Changes from v02 to v03

   Clarified high level description of implicit mode in Section 2.3
   (thanks to Kent for suggesting appropriate text).

   Clarified how IPv6 is tunneled over various tunneling modes allowed
   by MIPv4 in Section 4.3.2 (thanks to Alex for spotting this).

   Numerous editorial and clarification changes.

7.4.  Changes from v01 to v02

   Expanded high level description of explicit mode in Section 2.3.

   Fixed alignment of figures.

   Fixed length fields in extensions to reflect short extension format
   correctly (thanks to Jun Awano for catching this one)

   Removed section on Prefix Delegation and replaced it with more
   generic text that allows any other address allocation mechanism to be
   used to allocate IPv6 addresses and then extensions and mechanism
   described in this specification can be used to registered these
   addresses.

   Numerous editorial and clarification changes.






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7.5.  Changes from v00 to v01

   The Home Agent Considerations section was re-written and expanded
   with a lot more details by adapting text from MIPv6 and NEMO
   specifications.

   New error codes were added to section 3.2

   Allowed for any length prefix, not just 64 and 128.

   Numerous editorial and clarification changes.








































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8.  Acknowledgements

   Thanks to Pat Calhoun, Paal Engelstad, Tom Hiller and Pete McCann for
   earlier work on this subject.  Thanks also to Alex Petrescu for
   suggesting the use of additional mechanisms for dynamic IPv6 address
   allocation.  Special thanks also to Sri Gundavelli and Kent Leung for
   their thorough review and suggestions.












































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9.  Normative References

   [RFC2004]  Perkins, C., "Minimal Encapsulation within IP", RFC 2004,
              October 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 2434,
              October 1998.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

   [RFC2710]  Deering, S., Fenner, W., and B. Haberman, "Multicast
              Listener Discovery (MLD) for IPv6", RFC 2710,
              October 1999.

   [RFC2784]  Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
              Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
              March 2000.

   [RFC3024]  Montenegro, G., "Reverse Tunneling for Mobile IP,
              revised", RFC 3024, January 2001.

   [RFC3344]  Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
              August 2002.

   [RFC3519]  Levkowetz, H. and S. Vaarala, "Mobile IP Traversal of
              Network Address Translation (NAT) Devices", RFC 3519,
              May 2003.

   [RFC3775]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
              in IPv6", RFC 3775, June 2004.

   [RFC3810]  Vida, R. and L. Costa, "Multicast Listener Discovery
              Version 2 (MLDv2) for IPv6", RFC 3810, June 2004.

   [RFC3963]  Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
              Thubert, "Network Mobility (NEMO) Basic Support Protocol",
              RFC 3963, January 2005.

   [RFC4213]  Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
              for IPv6 Hosts and Routers", RFC 4213, October 2005.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.



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   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              September 2007.

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862, September 2007.













































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Authors' Addresses

   George Tsirtsis
   Qualcomm

   Phone: +908-947-7059
   Email: tsirtsis@qualcomm.com; tsirtsisg@yahoo.com


   Vincent Park
   Qualcomm

   Phone: +908-947-7084
   Email: vpark@qualcomm.com


   Hesham Soliman
   Elevate Technologies

   Phone: +614-111-410-445
   Email: hesham@elevatemobile.com






























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Full Copyright Statement

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   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

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