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Versions: 00 01 02 03 04 05 06 07 RFC 5026

MIP6 WG                                           G. Giaretta, Editor
Internet Draft                                         Telecom Italia
Expires: June 19, 2007                                       J. Kempf
                                                      DoCoMo Labs USA
                                                       V. Devarapalli
                                                      Azaire Networks
                                                    December 19, 2006



              Mobile IPv6 bootstrapping in split scenario
               draft-ietf-mip6-bootstrapping-split-04.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
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   BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on June 19, 2007.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   A Mobile IPv6 node requires a Home Agent address, a home address,
   and IPsec security associations with its Home Agent before it can
   start utilizing Mobile IPv6 service. RFC 3775 requires that some
   or all of these are statically configured. This document defines
   how a Mobile IPv6 node can bootstrap this information from non-



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   topological information and security credentials preconfigured on
   the Mobile Node. The solution defined in this document solves the
   bootstrapping problem from draft-ietf-mip6-bootstrapping-ps-02
   when the Mobile Node's mobility service is authorized by a
   different service provider than basic network access, and is
   therefore generically applicable to any bootstrapping case.

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].








































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Table of Contents

   1. Introduction...................................................4
   2. Terminology....................................................5
   3. Split scenario.................................................6
   4. Components of the solution.....................................9
   5. Protocol Operations...........................................11
      5.1. Home Agent Address Discovery.............................11
         5.1.1. DNS lookup by Home Agent Name.......................11
         5.1.2. DNS lookup by service name..........................12
         5.1.3. Anycast Address for Home Agent Assignment...........13
      5.2. IPsec Security Associations setup........................13
         5.2.1. IKEv2 Transaction With Anycast Home Agent Assignment14
      5.3. Home Address assignment..................................15
         5.3.1. Home Address assignment by the Home Agent...........15
         5.3.2. Home Address auto-configuration by the Mobile Node..15
      5.4. Authorization and Authentication with MSA................17
   6. Home Address registration in the DNS..........................19
   7. Summary of Bootstrapping Protocol Flow........................21
   8. Option and Attribute Format...................................23
      8.1. DNS Update mobility option...............................23
      8.2. MIP6_HOME_PREFIX attribute...............................24
   9. Security Considerations.......................................26
      9.1. HA Address Discovery.....................................26
      9.2. Home Address Assignment through IKEv2....................27
      9.3. SA Establishment Using EAP Through IKEv2.................28
      9.4. Back End Security Between the HA and AAA Server..........28
      9.5. Dynamic DNS Update.......................................28
   10. IANA Considerations..........................................30
   11. Contributors.................................................31
   12. Acknowledgments..............................................32
   13. References...................................................33
      13.1. Normative References....................................33
      13.2. Informative References..................................33
   Authors' Addresses...............................................35


















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1. Introduction

   Mobile IPv6 [2] requires the Mobile Node to know its Home Agent
   Address, its own Home Address and the cryptographic materials
   (e.g. shared keys or certificates) needed to set up IPsec security
   associations with the Home Agent in order to protect Mobile IPv6
   signaling. This is generally referred to as the Mobile IPv6
   bootstrapping problem [4].

   Mobile IPv6 base protocol does not specify any method to
   automatically acquire this information, which means that network
   administrators are normally required to manually set configuration
   data on Mobile Nodes and HAs. However, in real deployments, manual
   configuration does not scale as the Mobile Nodes increase in
   number.

   As discussed in [4], several bootstrapping scenarios can be
   identified depending on the relationship between the network
   operator that authenticates a mobile node for granting network
   access service (Access Service Authorizer, ASA) and the service
   provider that authorizes Mobile IPv6 service (Mobility Service
   Authorizer, MSA). This document describes a solution to the
   bootstrapping problem that is applicable in a scenario where the
   MSA and the ASA are different entities (i.e. split scenario).





























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2. Terminology

   General mobility terminology can be found in [10]. The following
   additional terms are used here:

   ASA
       Access Service Authorizer. A network operator that
       authenticates a mobile node and establishes the mobile node's
       authorization to receive Internet service.

   ASP
       Access Service Provider. A network operator that provides
       direct IP packet forwarding to and from the end host.

   MSA
       Mobility Service Authorizer. A service provider that
       authorizes Mobile IPv6 service.

   MSP
       Mobility Service Provider. A service provider that provides
       Mobile IPv6 service.  In order to obtain such service, the
       mobile node must be authenticated and prove authorization to
       obtain the service.

   Split scenario
       A scenario where mobility service and network access service
       are authorized by different entities. This implies that MSA is
       different from ASA.

























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3. Split scenario

   In the problem statement description [4] there is a clear
   assumption that mobility service and network access service can be
   separate. This assumption implies that mobility service and
   network access service may be authorized by different entities. As
   an example, the service model defined in [4] allows an enterprise
   network to deploy a Home Agent and offer Mobile IPv6 service to a
   user, even if the user is accessing the Internet independent of
   its enterprise account (e.g., by using his personal WiFi hotspot
   account at a coffee shop).

   Therefore, in this document it is assumed that network access and
   mobility service are authorized by different entities, which means
   that authentication and authorization for mobility service and
   network access will be considered separately. This scenario is
   called split scenario.

   Moreover, the model defined in [4] separates the entity providing
   the service from the entity that authenticates and authorizes the
   user. This is similar to the roaming model for network access.
   Therefore, in the split scenario, two different cases can be
   identified depending on the relationship between the entity that
   provides the mobility service (i.e. Mobility Service Provider,
   MSP) and the entity that authenticates and authorizes the user
   (i.e. Mobility Service Authorizer, MSA).

   Figure 1 depicts the split scenario when the MSP and the MSA are
   the same entity. This means that the network operator that
   provides the Home Agent authenticates and authorizes the user for
   mobility service..

                                        Mobility Service
                                 Provider and Authorizer
            +-------------------------------------------+
            |                                           |
            |  +-------------+                   +--+   |
            |  | MSA/MSP AAA |  <------------->  |HA|   |
            |  |   server    |    AAA protocol   +--+   |
            |  +-------------+                          |
            |                                           |
            +-------------------------------------------+

                       +--+
                       |MN|
                       +--+

                 Figure 1 - Split Scenario (MSA == MSP)

   Figure 2 shows the split scenario in case the MSA and the MSP are
   two different entities. This might happen if the Mobile Node is


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   far from its MSA network and is assigned a closer HA to optimize
   performance or if the MSA cannot provide any Home Agent and relies
   on a third party (i.e. the MSP) to grant mobility service to its
   users. Notice that the MSP might be or might not also be the
   network operator that is providing network access (i.e. ASP,
   Access Service Provider).

                Mobility Service
                      Authorizer
               +-------------+
               |  MSA AAA    |
               |   server    |
               +-------------+
                     ^
                     |
        AAA protocol |
                     |                  Mobility Service
                     |                          Provider
            +--------|----------------------------------+
            |        V                                  |
            |  +-------------+                   +--+   |
            |  |  MSP AAA    |  <------------->  |HA|   |
            |  |   server    |    AAA protocol   +--+   |
            |  +-------------+                          |
            |                                           |
            +-------------------------------------------+

                       +--+
                       |MN|
                       +--+

                 Figure 2 - Split Scenario (MSA != MSP)

   Note that Figure 1 and Figure 2 assume the use of an AAA protocol
   to authenticate and authorize the Mobile Node for mobility
   service. However, since IKEv2 allows EAP client authentication
   only and the server authentication needs to be performed based on
   certificates or public keys, the Mobile Node potentially requires
   a certificate revocation list check (CTL check) even though an AAA
   potocol is used to authenticate and authorize the Mobile Node for
   mobility service.

   If, instead, a PKI is used, the Mobile Node and HA exchange
   certificates and there is no AAA server involved [23]. This is
   conceptually similar to Figure 1, since the MSP == MSA, except the
   Home Agent, and potentially the Mobile Node, may require a
   certificate revocation list check (CRL check) with the Certificate
   Authority (CA). The CA may be either internal or external to the
   MSP. Figure 3 illustrates.




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                       Certificate
                        Authority
                      +-------------+
                      |    CA       |
                      |   server    |
                      +-------------+
                            ^
                            |
               CRL Check    |
                            |       Mobility Service
                            |    Provider and Authorizer
                   +--------|----------+
                   |        V          |
                   |  +-------------+  |
                   |  |     HA      |  |
                   |  |             |  |
                   |  +-------------+  |
                   |                   |
                   +-------------------+

                              +--+
                              |MN|
                              +--+

                   Figure 3 - Split Scenario with PKI

   The split scenario is the simplest model that can be identified,
   since no assumptions about the access network are made. This
   implies that the mobility service is bootstrapped independently
   from the authentication protocol for network access used (e.g.
   PANA, EAP). For this reason, the solution described in this
   document and developed for this scenario could also be applied to
   the integrated access network deployment model [4], even if it
   might not be optimized.











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4. Components of the solution

   The bootstrapping problem is composed of different sub-problems
   that can be solved independently in a modular way. The components
   identified and a brief overview of their solution follow.

   o  HA address discovery. The Mobile Node needs to discover the
      address of its Home Agent. The main objective of a
      bootstrapping solution is to minimize the data pre-configured
      on the Mobile Node. For this reason, the DHAAD defined in [2]
      may not be applicable in real deployments since it is required
      that the Mobile Node is pre-configured with the home network
      prefix and it does not allow an operator to load balance by
      having Mobile Nodes dynamically assigned to Home Agents located
      in different subnets. This document defines a solution for Home
      Agent address discovery that is based on Domain Name Service
      (DNS), introducing a new DNS SRV record [5]. The unique
      information that needs to be pre-configured on the Mobile Node
      is the domain name of the MSP.

   o  IPsec Security Associations setup. Mobile IPv6 requires that a
      Mobile Node and its Home Agent share an IPsec SA in order to
      protect binding updates and other Mobile IPv6 signaling. This
      document provides a solution that is based on IKEv2 and follows
      what is specified in [6]. The IKEv2 peer authentication can be
      performed both using certificates and using EAP, depending on
      the network operator's deployment model.

   o  Home Address (HoA) assignment. The Mobile Node needs to know
      its Home Address in order to bootstrap Mobile IPv6 operation.
      The Home Address is assigned by the Home Agent during the IKEv2
      exchange (as described in [6]). The solution defined in this
      document also allows the Mobile Node to auto-configure its Home
      Address based on stateless auto-configuration ([22]),
      Cryptographically Generated Addresses ([11]) or privacy
      addresses ([12]).

   o  Authentication and Authorization with MSA. The user must be
      authenticated in order for the MSP to grant the service. Since
      the user credentials can be verified only by the MSA, this
      authorization step is performed by the MSA. Moreover, the
      mobility service must be explicitly authorized by the MSA based
      on the user's profile. These operations are performed in
      different ways depending on the credentials used by the Mobile
      Node during the IKEv2 peer authentication and on the backend
      infrastructure (PKI or AAA).

   An optional part of bootstrapping involves providing a way for the
   Mobile Node to have its FQDN updated in the DNS with a dynamically
   assigned home address. While not all applications will require
   this service, many networking applications use the FQDN to obtain


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   an address for a node prior to starting IP traffic with it. The
   solution defined in this document specifies that the dynamic DNS
   update is performed by the Home Agent or through the AAA
   infrastructure, depending on the trust relationship in place.

















































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5. Protocol Operations

   This section describes in detail the procedures needed to perform
   Mobile IPv6 bootstrapping based on the components identified in
   the previous section.



5.1. Home Agent Address Discovery

   Once a Mobile Node has obtained network access, it can perform
   Mobile IPv6 bootstrapping. For this purpose, the Mobile Node
   queries the DNS server to request information on Home Agent
   service. As mentioned before in the document, the only information
   that needs to be pre-configured on the Mobile Node is the domain
   name of the Mobility Service Provider.

   The Mobile Node needs to obtain the IP address of the DNS server
   before it can send a DNS request. This can be pre-configured on
   the Mobile Node or obtained through DHCPv6 from the visited link
   [13]. In any case, it is assumed that there is some kind of
   mechanism by which the Mobile Node is configured with a DNS server
   since a DNS server is needed for many other reasons.

   Two options for DNS lookup for a Home Agent address are identified
   in this document: DNS lookup by Home Agent Name and DNS lookup by
   service name.

   This document does not provide a specific mechanism to load
   balance different Mobile Nodes among Home Agents. It is possible
   for an MSP to achieve coarse-grained load balancing by dynamically
   updating the SRV RR priorities to reflect the current load on the
   MSP's collection of Home Agents. Mobile Nodes then use the
   priority mechanism to preferentially select the least loaded HA.
   The effectiveness of this technique depends on how much of a load
   it will place on the DNS servers, particularly if dynamic DNS is
   used for frequent updates.

   While this document specifies a Home Agent Address Discovery
   solution based on DNS, when the ASP and the MSP are the same
   entity DHCP may be used. See [17] for details.

5.1.1. DNS lookup by Home Agent Name

   In this case, the Mobile Node is configured with the Fully
   Qualified Domain Name of the Home Agent. As an example, the Mobile
   Node could be configured with the name "ha1.example.com", where
   "example.com" is the domain name of the MSP granting the mobility
   service.




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   The Mobile Node constructs a DNS request, by setting the QNAME to
   the name of the Home Agent. The request has QTYPE set to 'AAAA',
   so that the DNS server sends the IPv6 address of the Home Agent.
   Once the DNS server replies to this query, the Mobile Node knows
   its Home Agent address and can run IKEv2 in order to set up the
   IPsec SAs and get a Home Address.

   Additionally, the ability to provide a mobile node with a
   localized home agent (e.g. on the visited link) can help to
   optimize handover signaling and improve routing efficiency in bi-
   directional tunneling mode. There are a variety of ways this can
   be achieved in an interoperable way. One way is to provision the
   mobile node with an FQDN for a local home agent when it configures
   for the local link. Another way is to specify an interoperable
   naming convention for constructing home agent FQDNs based on
   location. For example, an operator might assign the FQDN
   "ha.locationA.operator.com" to the Home Agent located in "location
   A" and the FQDN "ha.locationB.operator.com" to the Home Agent
   located in "location B". If the Mobile Node wants to use a Home
   Agent located in "location A", it will set the QNAME to
   "ha.locationA.operator.com" in the DNS request. The exact way in
   which localized Home Agents are configured is out of scope for
   this draft.

5.1.2. DNS lookup by service name

   RFC 2782 [5] defines the service resource record (SRV RR) that
   allows an operator to use several servers for a single domain, to
   move services from host to host, and to designate some hosts as
   primary servers for a service and others as backups. Clients ask
   for a specific service/protocol for a specific domain and get back
   the names of any available servers.

   RFC 2782[5] also describes the policies to choose a service agent
   based on the preference and weight values. The DNS SRV record may
   contain the preference and weight values for multiple Home Agents
   available to the Mobile Node in addition to the Home Agent FQDNs.
   If multiple Home Agents are available in the DNS SRV record then
   Mobile Node is responsible for processing the information as per
   policy and for picking one Home Agent. If the Home Agent of choice
   does not respond for some reason or the IKEv2 authentication
   fails, the Mobile Node SHOULD try other Home Agents on the list.

   The service name for Mobile IPv6 Home Agent service as required by
   RFC 2782 is "mip6" and the protocol name is "ipv6". Note that a
   transport name cannot be used here because Mobile IPv6 does not
   run over a transport protocol.

   The SRV RR has a DNS type code of 33. As an example, the Mobile
   constructs a request with QNAME set to "_mip6._ipv6.example.com"
   and QTYPE to SRV. The reply contains the FQDNs of one or more


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   servers, that can then be resolved in a separate DNS transaction
   to the IP addresses. However, if there is room in the SRV reply,
   it is RECOMMENDED that the DNS server also return the IP addresses
   of the Home Agents in AAAA records as part of the additional data
   section (in order to avoid requiring an additional DNS round trip
   to resolve the FQDNs).

5.1.3. Anycast Address for Home Agent Assignment

   A FQDN MAY be bound to an IPv6 anycast address rather than to a
   unicast address for a Home Agent. Since anycast addresses are
   indistinguishable from unicast addresses, there is no distinction
   in the AAAA record between a unicast address and an anycast
   address. The anycast address allows the home network to assign a
   Home Agent to a Mobile Node on a case by case basis at the time
   that the Mobile Node bootstraps, rather than having the Mobile
   Node select the Home Agent address. Section 5.2.1. below describes
   how the IKEv2 transaction is modified by anycast Home Agent
   assignment. A FQDN bound to an anycast address MAY be returned by
   a SRV RR query. Mobile Nodes that implement this specification
   MUST be prepared to handle an anycast address for Home Agent
   assignment.

   The anycast address reserved by RFC 2526 [8] for Home Agents on
   the same link MAY be used for bootstrapping. Other deployment-
   specific anycast addresses, spanning a wider topology, MAY also be
   used.

   Note that anycast forwarding as specified in RFC 4291 [9] allows
   the node which has the anycast address assigned to one of its
   network interfaces to make the decision about to which address
   forwarding should occur based only on routing metric information.
   Use of any other criteria, such as load balancing or service
   profile offered by the Home Agent, in a standardized way is
   currently unsupported. Assignment based on other criteria than
   routing metrics can be achieved by having the home agent receiving
   the forwarded message perform the home agent selection based on
   other critera, but the mechanism for this is out of scope of this
   draft.



5.2. IPsec Security Associations setup

   As soon as the Mobile Node has discovered the Home Agent Address,
   it establishes an IPsec Security Association with the Home Agent
   itself through IKEv2. The detailed description of this procedure
   is provided in [6]. If the Mobile Node wants the HA to register
   the Home Address in the DNS, it MUST use the FQDN as the initiator
   identity in IKE_AUTH step of the IKEv2 exchange (IDi). This is
   needed because the Mobile Node has to provide it is the owner of


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   the FQDN provided in the subsequent DNS Update Option. See section
   6 and section 9 for a more detailed analysis on this issue.

   The IKEv2 Mobile Node to Home Agent authentication can be
   performed using either IKEv2 public key signatures or the
   Extensible Authentication Protocol (EAP). The details about how to
   use IKEv2 authentication are described in [6] and [7]. Choice of
   an IKEv2 peer authentication method depends on the deployment.
   However, IKEv2 restricts the Home Agent to Mobile Node
   authentication to use public key signature-based authentication.

5.2.1. IKEv2 Transaction With Anycast Home Agent Assignment

   If an anycast address is returned in response to DNS resolution of
   an FQDN, the IKEv2 transaction between the Mobile Node and Home
   Agent is slightly modified. The Mobile Node sends the IKE_SA_INIT
   request to the anycast address. The node which has the anycast
   address assigned to one of its network interfaces selects a Home
   Agent address from the set of Home Agents managed by the node, and
   forwards the IKE_SA_INIT. If the set of Home Agents is empnty, the
   node simply drops the packet. The Home Agent answers using its own
   address, and includes an "under attack" cookie, in accordance with
   RFC 4306 [7]. The Mobile Node notes the Home Agent address and
   resends the IKE_SA_INIT message to the Home Agent, along with the
   cookie.

   The resulting IKE_SA_INIT transaction is the following:



        Initiator                         Responder ("best" HA)
       -----------                        ---------------------

       (IP_I:500 -> ANYCAST:500)
       HDR(A,0), SAi1, KEi, Ni   -->


                                 (IP_R:500 -> IP_I:500)
                             <-- HDR(A,0), N(COOKIE)


       (IP_I:500 -> IP_R:500)
       HDR(A,0), N(COOKIE), SAi1, KEi, Ni  -->


                                 (IP_R:500 -> IP_I:500)
                             <-- HDR(A,B), SAr1, KEr, Nr,[CERTREQ]



       (IP_I:500 -> IP_R:500)


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       HDR(A,B), SK {IDi, [CERT,] [CERTREQ,]
       [IDr,]AUTH, SAi2, TSi, TSr} -->

                                 (IP_R:500 -> IP_I:500)
                             <-- HDR(A,B), SK {IDr, [CERT,] AUTH,
                                                 SAr2, TSi, TSr}


   Note that this procedure requires the implementation of anycast
   forwarding in such a way that the Home Agent can distinguish
   between an IKE_SA_INIT forwarded through an anycast address and
   one sent directly from the Mobile Node. Home Agents SHOULD NOT
   include an "under attack" cookie unless the IKE_SA_INIT was
   forwarded through an anycast address or the Home Agent believes
   that it is, in fact, under attack, in order to maintain
   conformance with RFC 4306 for other applications.



5.3. Home Address assignment

   Home Address assignment is performed during the IKEv2 exchange.
   The Home Address can be assigned directly by the Home Agent or can
   be auto-configured by the Mobile Node.

5.3.1. Home Address assignment by the Home Agent

   When the Mobile Node runs IKEv2 with its Home Agent, it can
   request a HoA through the Configuration Payload in the IKE_AUTH
   exchange by including an INTERNAL_IP6_ADDRESS attribute. When the
   Home Agent processes the message, it allocates a HoA and sends it
   a CFG_REPLY message. The Home Agent could consult a DHCP server on
   the home link for the actual home address allocation. This is
   explained in detail in [6].

5.3.2. Home Address auto-configuration by the Mobile Node

   With the type of assignment described in the previous section, the
   Home Address cannot be generated based on Cryptographically
   Generated Addresses (CGAs) [11] or based on the privacy extensions
   for stateless auto-configuration [12]. However, the Mobile Node
   might want to have an auto-configured HoA based on these
   mechanisms. It is worthwhile to mention that the auto-
   configuration procedure described in this section cannot be used
   in some possible deployments, since the Home Agents might be
   provisioned with pools of allowed Home Addresses.

   In the simplest case, the Mobile Node is provided with a pre-
   configured home prefix and home prefix length. In this case the
   Mobile Node creates a Home Address based on the pre-configured
   prefix and sends it to the Home Agent including an


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   INTERNAL_IP6_ADDRESS attribute in a Configuration Payload of type
   CFG_REQUEST. If the Home Address is valid, the Home Agent replies
   with a CFG_REPLY, including an INTERNAL_IP6_ADDRESS with the same
   address. If the Home Address provided by the Mobile Node is not
   valid, the Home Agent assigns a different Home Address including
   an INTERNAL_IP6_ADDRESS attribute with a new value. According to
   [7] the Mobile Node MUST use the address sent by the Home Agent.
   Later, if the Mobile Node wants to use an auto-configured Home
   Address (e.g. based on CGA), it can run Mobile Prefix Discovery,
   obtain a prefix, auto-configure a new Home Address and then
   perform a new CREATE_CHILD_SA exchange.

   If the Mobile Node is not provided with a pre-configured Home
   Prefix, the Mobile cannot simply propose an auto-configured HoA in
   the Configuration Payload since the Mobile Node does not know the
   home prefix before the start of the IKEv2 exchange. The Mobile
   Node must obtain the home prefix and the home prefix length before
   it can configure a home address.

   One simple solution would be for the Mobile Node to just assume
   that the prefix length on the home link is 64 bits and extract the
   home prefix from the Home Agent's address. The disadvantage with
   this solution is that the home prefix cannot be anything other
   than /64. Moreover, this ties the prefix on the home link and the
   Home Agent's address, but, in general, a Home Agent with a
   particular address should be able to serve a number of prefixes on
   the home link, not just the prefix from which its address is
   configured.

   Another solution would be for the Mobile Node to assume that the
   prefix length on the home link is 64 bits and send its interface
   identifier to the Home Agent in the INTERNAL_IP6_ADDRESS attribute
   within the CFG_REQ payload. Even though this approach does not tie
   the prefix on the home link and the Home Agent's address, it still
   requires that the home prefix length is 64 bits.

   For this reason the Mobile Node needs to obtain the home link
   prefixes through the IKEv2 exchange. In the Configuration Payload
   during the IKE_AUTH exchange, the Mobile Node includes the
   MIP6_HOME_PREFIX attribute in the CFG_REQUEST message.  The Home
   Agent, when it processes this message, should include in the
   CFG_REPLY payload prefix information for one prefix on the home
   link. This prefix information includes the prefix length (see
   section 8.2). The Mobile Node auto-configures a Home Address from
   the prefix returned in the CFG_REPLY message and runs a
   CREATE_CHILD_SA exchange to create security associations for the
   new Home Address.

   As mentioned before in this document, there are deployments where
   auto-configuration of the Home Address cannot be used. In this
   case, when the Home Agent receives a CFG_REQUEST including a


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   MIP6_HOME_PREFIX attribute, in the subsequent IKE response it
   includes a Notify Payload type "USE_ASSIGNED_HoA" and the related
   Home Address in a INTERNAL_IP6_ADDRESS attribute. If the Mobile
   Node gets a "USE_ASSIGNED_HoA" Notify Payload in response to the
   Configuration Payload containing the MIP6_HOME_PREFIX attribute,
   it looks for an INTERNAL_IP6_ADDRESS attribute and MUST use the
   address contained in it in the subsequent CREATE_CHILD_SA
   exchange.

   When the Home Agent receives a Binding Update for the Mobile Node,
   it performs proxy DAD for the auto-configured Home Address. If DAD
   fails, the Home Agent rejects the Binding Update. If the Mobile
   Node receives a Binding Acknowledgement with status 134 (DAD
   failed), it MUST stop using the current Home Address, configure a
   new HoA, and then run IKEv2 CREATE_CHILD_SA exchange to create
   security associations based on the new HoA. The Mobile Node does
   not need to run IKE_INIT and IKE_AUTH exchanges again. Once the
   necessary security associations are created, the Mobile Node sends
   a Binding Update for the new Home Address.

   It is worth noting that with this mechanism, the prefix
   information carried in MIP6_HOME_PREFIX attribute includes only
   one prefix and does not carry all the information that is
   typically present when received through a IPv6 router
   advertisement. Mobile Prefix Discovery, specified in RFC 3775 [2],
   is the mechanism through which the Mobile Node can get all
   prefixes on the home link and all related information. That means
   that MIP6_HOME_PREFIX attribute is only used for Home Address
   auto-configuration and does not replace the usage of Mobile Prefix
   Discovery for the purposes detailed in RFC 3775.



5.4. Authorization and Authentication with MSA

   In a scenario where the Home Agent is discovered dynamically by
   the Mobile Node, it is very likely that the Home Agent is not able
   to verify by its own the credentials provided by the Mobile Node
   during the IKEv2 exchange. Moreover, the mobility service needs to
   be explicitly authorized based on the user's profile. As an
   example, the Home Agent might not be aware of whether the mobility
   service can be granted at a particular time of the day or when the
   credit of the Mobile Node is going to expire.

   Due to all these reasons, the Home Agent may need to contact the
   MSA in order to authenticate the Mobile Node and authorize
   mobility service. This can be accomplished based on a Public Key
   Infrastructure if certificates are used and a PKI is deployed by
   the MSP and MSA. On the other hand, if the Mobile Node is provided
   with other types of credentials, the AAA infrastructure must be
   used.


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   The definition of this backend communication is out of the scope
   of this document. In [14] a list of goals for such a communication
   is provided.


















































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6. Home Address registration in the DNS

   In order that the Mobile Node is reachable through its dynamically
   assigned Home Address, the DNS needs to be updated with the new
   Home Address. Since applications make use of DNS lookups on FQDN
   to find a node, the DNS update is essential for providing IP
   reachability to the Mobile Node, which is the main purpose of the
   Mobile IPv6 protocol. The need for DNS updating is not discussed
   in RFC 3775 since it assumes that the Mobile Node is provisioned
   with a static Home Address. However, when a dynamic Home Address
   is assigned to the Mobile Node, any existing DNS entry becomes
   invalid and the Mobile Node becomes unreachable unless a DNS
   update is performed.

   Since the DNS update must be performed securely in order to
   prevent attacks or modifications from malicious nodes, the node
   performing this update must share a security association with the
   DNS server. Having all possible Mobile Nodes sharing a security
   association with the DNS servers of the MSP might be cumbersome
   from an administrative perspective. Moreover, even if a Mobile
   Node has a security association with a DNS server of its MSP, an
   address authorization issue comes into the picture. A detailed
   analysis of possible threats against DNS update is provided in
   section 9.5.

   Therefore, due to security and administrative reasons, it is
   RECOMMENDED that the Home Agent perform DNS entry updates for the
   Mobile Node. For this purpose the Mobile Node MAY include a new
   mobility option in the Binding Update, the DNS Update option, with
   the flag R not set in the option. This option is defined in
   section 8 and includes the FQDN that needs to be updated. After
   receiving the Binding Update, the Home Agent MUST update the DNS
   entry with the identifier provided by the Mobile Node and the Home
   Address included in the Home Address Option. The procedure for
   sending a dynamic DNS update message is specified in [16]. The
   dynamic DNS update SHOULD be performed in a secure way; for this
   reason, the usage of TKEY and TSEC or DNSSEC is recommended (see
   section 9.5. for details). As soon as the Home Agent has updated
   the DNS, it MUST send a Binding Acknowledgement message to the
   Mobile Node including the DNS Update mobility option with the
   correct value in the Status field (see section 8.1).

   This procedure can be performed directly by the Home Agent if the
   Home Agent has a security association with the domain specified in
   the Mobile Node's FQDN.

   On the other hand, if the Mobile Node wants to be reachable
   through a FQDN that belongs to the MSA, the Home Agent and the DNS
   server that must be updated belong to different administrative
   domains. In this case the Home Agent may not share a security
   association with the DNS server and the DNS entry update can be


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   performed by the AAA server of the MSA. In order to accomplish
   this, the Home Agent sends to the AAA server the FQDN-HoA pair
   through the AAA protocol. This message is proxied by the AAA
   infrastructure of the MSP and is received by the AAA server of the
   MSA. The AAA server of the MSA perform the DNS update based on
   [16]. Notice that, even in this case, the Home Agent is always
   required to perform a DNS update for the reverse entry, since this
   is always performed in the DNS server of the MSP. The detailed
   description of the communication between Home Agent and AAA is out
   of the scope of this document. More details are provided in [14].

   A mechanism to remove stale DNS entries is needed. A DNS entry
   becomes stale when the related Home Address is no longer used by
   the Mobile Node. To remove a DNS entry, the Mobile Node includes
   in the Binding Update the DNS Update mobility option, with the
   flag R set in the option. After receiving the Binding Update, the
   Home Agent MUST remove the DNS entry identified by the FQDN
   provided by the Mobile Node and the Home Address included in the
   Home Address Option. The procedure for sending a dynamic DNS
   update message is specified in [16]. As mentioned above, the
   dynamic DNS update SHOULD be performed in a secure way; for this
   reason, the usage of TKEY and TSEC or DNSSEC is recommended (see
   section 9.5. for details).

   If there is no explicit de-registration BU from the Mobile Node,
   then the HA MAY use the binding cache entry expiration as a
   trigger to remove the DNS entry.


























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7. Summary of Bootstrapping Protocol Flow

   The message flow of the whole bootstrapping procedure when the
   dynamic DNS update is performed by the Home Agent is depicted in
   Figure 4.

       +----+                  +----+              +-----+
       | MN |                  | HA |              | DNS |
       +----+                  +----+              +-----+

              IKEv2 exchange
           (HoA configuration)
          <======================>

          BU (DNS update option)
          ----------------------->
                                        DNS update
                                  <------------------->
           BA (DNS update option)
          <-----------------------


                Figure 4 - Dynamic DNS update by the HA



   Figure 5 shows the message flow of the whole bootstrapping
   procedure when the dynamic DNS update is performed by the AAA
   server of the MSA.
























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     +----+                +----+         +---+         +---+
     | MN |                | HA |         |AAA|         |DNS|
     +----+                +----+         +---+         +---+

           IKEv2 exchange
         (HoA configuration)
       <======================>

       BU (DNS update option)
       ----------------------->

                                AAA request
                                (FQDN, HoA)
                              <-------------->

                                               DNS update
                                              <----------->
                                AAA answer
                                (FQDN, HoA)
                              <-------------->
         BA (DNS update option)
       <-----------------------


                Figure 5 - Dynamic DNS update by the AAA

   Notice that, even in this last case, the Home Agent is always
   required to perform a DNS update for the reverse entry, since this
   is always performed in the DNS server of the MSP. This is not
   depicted in Figure 5.























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8. Option and Attribute Format

8.1. DNS Update mobility option

   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
                                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                   |  Option Type  | Option Length |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Status      |R|  Reserved   |     MN identity (FQDN) ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   o  Option Type - DNS-UPDATE-TYPE to be defined by IANA

   o  Option Length - 8 bit unsigned integer indicating the length of
      the option excluding the type and length fields

   o  Status - 8 bit unsigned integer indicating the result of the
      dynamic DNS update procedure. This field MUST be set to 0 and
      ignored by the receiver when the DNS Update mobility option is
      included in a Binding Update message. When the DNS Update
      mobility option is included in the Binding Acknowledgement
      message, values of the Status field less than 128 indicate that
      the dynamic DNS update was performed successfully by the Home
      Agent. Values greater than or equal to 128 indicate that the
      dynamic DNS update was not completed by the HA. The following
      Status values are currently defined:

          0 DNS update performed

          128 Reason unspecified

          129 Administratively prohibited

          130 DNS Update Failed

   o  R flag - if set the Mobile Node is requesting the HA to remove
      the DNS entry identified by the FQDN specified in this option
      and the HoA of the Mobile Node. If not set, the Mobile Node is
      requesting the HA to create or update a DNS entry with its HoA
      and the FQDN specified in the option.

   o  Reserved - these bits are reserved for future purposes and MUST
      be set to 0.

   o  MN identity - the identity of the Mobile Node to be used by the
      Home Agent to send a Dynamic DNS update.  It is a variable
      length field.




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8.2. MIP6_HOME_PREFIX attribute

   The MIP6_HOME_PREFIX attribute is included in the IKEv2
   CFG_REQUEST by the Mobile Node to ask the Home Agent for the home
   prefix and is included in the CFG_REPLY by the Home Agent to
   provide the Mobile Node with home prefix and home prefix length.
   The format of this attribute is equal to the format of the
   Configuration Attributes defined in [7] and is depicted below.

                         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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |R|                     Attribute Type                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         Length                |           Prefix Length       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |                        home prefix                            |
    |                                                               |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     Prefix Lifetime                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



   o  Reserved (1 bit) - This bit MUST be set to zero and MUST be
      ignored on receipt.

   o  Attribute Type (15 bits) - A unique identifier for the
      MIP6_HOME_PREFIX attribute. To be assigned by IANA.

   o  Length (2 octets) - Length in octets of Value field (home
      prefix and Prefix Length). This is multi-valued and can be 0 or
      17.

   o  Prefix Length (2 octets) - The length in bits of the home
      prefix specified in the field Home Prefix.

   o  Home Prefix (16 octets) - The prefix of the home link through
      which the Mobile Node must auto-configure its Home Address.

   o  Prefix Lifetime (4 octets) - The lifetime of the Home Prefix.

   When the MIP6_HOME_PREFIX attribute is included by the Mobile Node
   in the CFG_REQUEST payload, the value of the Length field is 0. On
   the other hand, when the MIP6_HOME_PREFIX attribute is included in
   the CFG_REPLY payload by the Home Agent, the value of the Length
   field is 17 and the attribute contains also the Home Prefix and
   the Prefix Length fields.



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9. Security Considerations

9.1. HA Address Discovery

   Use of DNS for address discovery carries certain security risks.
   DNS transactions in the Internet are typically done without any
   authentication of the DNS server by the client or of the client by
   the server. There are two risks involved:

   1) A legitimate client obtains a bogus Home Agent address from a
   bogus DNS server. This is sometimes called a "pharming" attack,

   2) An attacking client obtains a legitimate Home Agent address
   from a legitimate server.

   The risk in Case 1 is mitigated because the Mobile Node is
   required to conduct an IKE transaction with the Home Agent prior
   to performing a Binding Update to establish Mobile IPv6 service.
   According to the IKEv2 specification [7], the responder must
   present the initiator with a valid certificate containing the
   responder's public key, and the responder to initiator IKE_AUTH
   message must be protected with an authenticator calculated using
   the public key in the certificate. Thus, an attacker would have to
   set up both a bogus DNS server and a bogus Home Agent, and
   provision the Home Agent with a certificate that a victim Mobile
   Node could verify. If the Mobile Node can detect that the
   certificate is not trustworthy, the attack will be foiled when the
   Mobile Node attempts to set up the IKE SA.

   The risk in Case 2 is limited for a single Mobile Node to Home
   Agent transaction if the attacker does not possess proper
   credentials to authenticate with the Home Agent. The IKE SA
   establishment will fail when the attacking Mobile Node attempts to
   authenticate itself with the Home Agent. Regardless of whether the
   Home Agent utilizes EAP or host-side certificates to authenticate
   the Mobile Node, the authentication will fail unless the Mobile
   Node has valid credentials.

   Another risk exists in Case 2 because the attacker may be
   attempting to propagate a DoS attack on the Home Agent. In that
   case, the attacker obtains the Home Agent address from the DNS,
   then propagates the address to a network of attacking hosts that
   bombard the Home Agent with traffic. This attack is not unique to
   the bootstrapping solution, however, it is actually a risk that
   any Mobile IPv6 Home Agent installation faces. In fact, the risk
   is faced by any service in the Internet that distributes a unicast
   globally routable address to clients. Since Mobile IPv6 requires
   that the Mobile Node communicate through a globally routable
   unicast address of a Home Agent, it is possible that the Home
   Agent address could be propagated to an attacker by various means
   (theft of the Mobile Node, malware installed on the Mobile Node,


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   evil intent of the Mobile Node owner him/herself, etc.) even if
   the home address is manually configured on the Mobile Node.
   Consequently, every Mobile IPv6 Home Agent installation will
   likely be required to mount anti-DoS measures. Such measures
   include overprovisioning of links to and from Home Agents and of
   Home Agent processing capacity, vigilant monitoring of traffic on
   the Home Agent networks to detect when traffic volume increases
   abnormally indicating a possible DoS attack, and hot spares that
   can quickly be switched on in the event an attack is mounted on an
   operating collection of Home Agents. DoS attacks of moderate
   intensity should be foiled during the IKEv2 transaction. IKEv2
   implementations are expected to generate their cookies without any
   saved state, and to time out cookie generation parameters
   frequently, with the timeout value increasing if a DoS attack is
   suspected. This should prevent state depletion attacks, and should
   assure continued service to legitimate clients until the practical
   limits on the network bandwith and processing capacity of the Home
   Agent network are reached.

   Explicit security measures between the DNS server and host, such
   DNSSEC [18] or TSIG/TKEY [19] [20] can mitigate the risk of 1) and
   2), but these security measures are not widely deployed on end
   nodes. These security measures are not sufficient to protect the
   Home Agent address against DoS attack, however, because a node
   having a legitimate security association with the DNS server could
   nevertheless intentionally or inadvertently cause the Home Agent
   address to become the target of DoS.

   Finally notice that assignment of an home agent from the serving
   network access provider's (local home agent) or a home agent from
   a nearby network (nearby home agent) may set up the potential to
   compromise a mobile node's location privacy. However, since a
   standardized mechanism of assigning local or nearby home agents is
   out of scope for this document, it is not possible to present
   detailed security considerations. Please see other drafts that
   contain detailed mechanisms for localized home agent assignment,
   such as [17], for information on the location privacy properties
   of particular home agent assignment mechanisms.

   Security considerations for discovering HA using DHCP are covered
   in draft-jang-dhc-haopt-01 [15].

9.2. Home Address Assignment through IKEv2

   Mobile IPv6 bootstrapping assigns the home address through the
   IKEv2 transaction. The Mobile Node can either choose to request an
   address, similar to DHCP, or the Mobile Node can request a prefix
   on the home link then auto-configure an address.

   RFC 3775 [2] and 3776 [3] require that a Home Agent check
   authorization of a home address received during a Binding Update.


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   The Home Agent MUST set up authorization by linking the home
   address to the identity of the IPsec SAs used to authenticate the
   Binding Update message. The linking MUST be done either during the
   IKE_AUTH phase or CREATE_CHILD_SA phase when the IPsec SAs are
   constructed.

   If the address is auto-configured, RFC 3775 requires the Home
   Agent to proxy-defend the address on the home link after the
   Mobile Node performs the initial Binding Update. Since it is not
   currently possible to securely proxy CGAs using SEND, attacks on
   address resolution for Neighbor Discovery listed in RFC 3756 are
   possible on dynamically assigned home addresses that are proxied
   by the Home Agent.

9.3. SA Establishment Using EAP Through IKEv2

   Security considerations for authentication of the IKE transaction
   using EAP are covered in draft-ietf-mip6-ikev2-ipsec [6].

9.4. Back End Security Between the HA and AAA Server

   Some deployments of Mobile IPv6 bootstrapping may use an AAA
   server to handle authorization for mobility service. This process
   has its own security requirements, but the back end protocol for
   Home Agent to AAA server interface is not covered in this draft.
   Please see draft-ietf-mip6-aaa-ha-goals [14] for a discussion of
   this interface.

9.5. Dynamic DNS Update

   Mobile IPv6 bootstrapping recommends the Home Agent to update the
   Mobile Node's FQDN with a dynamically assigned home address rather
   than have the Mobile Node itself do it (see Section 6 above). This
   choice was motivated by a concern for preventing redirection-based
   flooding attacks (see draft-ietf-mip6-ro-sec [21] for more
   information about redirection-based flooding attacks and the role
   preventing them played in the design of Mobile IPv6 route
   optimization security). Exactly as for route optimization, it is
   possible for a node that is the legitimate owner of a DNS FQDN -
   in the sense that it has a security association with the DNS
   server allowing it to perform dynamic DNS update of its FQDN - to
   bind its FQDN to the address of a victim, then redirect large
   volumes of traffic at the victim. The attack may be propagated
   without the owner's knowledge, for example, if the node is
   compromised by malware, or it may be intentional if the node
   itself is the attacker.

   While it is possible to prevent redirection attacks through
   ingress filtering on access routers, ISPs have little or no
   incentive to deploy ingress filtering. In some cases, if an attack
   could result in substantial financial gain, it is even possible


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   that a corrupt ISP may have an incentive not to deploy ingress
   filters such as has been the case for spam. Consequently, the
   security for dynamic Mobile Node FQDN update has been assigned to
   the Home Agent, where active network administration and vigilant
   defense measures are more likely to (but are not assured of)
   mitigating problems, and the owner of the Mobile Node is more
   likely to detect a problem if it occurs.

   If a Home Agent performs dynamic DNS update on behalf of the
   Mobile Node directly with the DNS server, the Home Agent MUST have
   a security association of some type with the DNS server. The
   security association MAY be established either using DNSSEC [18]
   or TSIG/TKEY [19][20]. A security association is required even if
   the DNS server is in the same administrative domain as the Home
   Agent. The security association SHOULD be separate from the
   security associations used for other purposes, such as AAA.

   In the case where the Mobility Service Provider is different from
   the Mobility Service Authorizer, the network administrators may
   want to limit the number of cross-administrative domain security
   associations. If the Mobile Node's FQDN is in the Mobility Service
   Authorizer's domain, since a security association for AAA
   signaling involved in mobility service authorization is required
   in any case, the Home Agent can send the Mobile Node's FQDN to the
   AAA server under the HA-AAA server security association, and the
   AAA server can perform the update. In that case, a security
   association is required between the AAA server and DNS server for
   the dynamic DNS update. See draft-ietf-mip6-aaa-ha-goals [14] for
   a deeper discussion of the Home Agent to AAA server interface.

   Regardless of whether the AAA server or Home Agent performs DNS
   update, the authorization of the Mobile Node to update a FQDN MUST
   be checked prior to the performance of the update. It is an
   implementation issue as to how authorization is determined.
   However, in order to allow this authorization step, the Mobile
   Node MUST use a FQDN as the IDi in IKE_AUTH step of the IKEv2
   exchange. The FQDN MUST be the same that will be provided by the
   Mobile Node in the DNS Update Option. This allows the Home Agent
   to get authorization information about the Mobile Node's FQDN via
   the AAA back end communication performed during IKEv2 exchange.
   The outcome of this step will give the Home Agent the necessary
   information to authorize the DNS update request of the Mobile
   Node. See draft-ietf-mip6-aaa-ha-goals [14] for details about the
   communication between the AAA server and the Home Agent needed to
   perform the authorization. Notice that if certificates are used in
   IKEv2, the authorization information about the FQDN for DNS update
   MUST be present in the certificate provided by the Mobile Node.






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10. IANA Considerations

   This document defines a new Mobility Option and a new IKEv2
   Configuration Attribute Type.

   The following values should be assigned:

   o  from "Mobility Option" namespace ([2]): DNS-UPDATE-TYPE
      (section 8.1)

   o  from "IKEv2 Configuration Payload Attribute Types" namespace
      ([7]): MIP6_HOME_PREFIX attribute (section 8.2)

   o  from "IKEv2 Notify Payload Error Types" namespace ([7]):
      USE_ASSIGNED_HoA error type (section 5.3.2)






































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11. Contributors

   This contribution is a joint effort of the bootstrapping solution
   design team of the MIP6 WG.  The contributors include Basavaraj
   Patil, Alpesh Patel, Jari Arkko, James Kempf, Yoshihiro Ohba,
   Gopal Dommety, Alper Yegin, Junghoon Jee, Vijay Devarapalli,
   Kuntal Chowdury, Julien Bournelle. Francis Dupont and Kilian
   Weniger have contributed on the anycast HA assignment procedure.

   The design team members can be reached at:

   Gerardo Giaretta  gerardo.giaretta@telecomitalia.it

   Basavaraj Patil   basavaraj.patil@nokia.com

   Alpesh Patel      alpesh@cisco.com

   Jari Arkko        jari.arkko@kolumbus.fi

   James Kempf       kempf@docomolabs-usa.com

   Yoshihiro Ohba    yohba@tari.toshiba.com

   Gopal Dommety     gdommety@cisco.com

   Alper Yegin       alper.yegin@samsung.com

   Vijay Devarapalli vijay.devarapalli@azairenet.com

   Kuntal Chowdury   kchowdury@starentnetworks.com

   Junghoon Jee      jhjee@etri.re.kr

   Julien Bournelle  julien.bournelle@int-evry.fr



















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12. Acknowledgments

   The authors would like to thank Rafa Lopez, Francis Dupont, Jari
   Arkko, Kilian Weniger, Vidya Narayanan, Ryuji Wakikawa, Michael Ye
   for their valuable comments.
















































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13. References

13.1. Normative References

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

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

   [3]   Arkko, J., Devarapalli, V., Dupont, F., "Using IPsec to
         Protect Mobile IPv6 Signaling between Mobile Nodes and
         Home Agents", RFC 3776, June 2004

   [4]   Patel, A., "Problem Statement for bootstrapping Mobile
         IPv6", Internet-Draft draft-ietf-mip6-bootstrap-ps-04,
         February 2006.

   [5]   Gulbrandsen, A., Vixie, P. and L. Esibov, "A DNS RR for
         specifying the location of services (DNS SRV)", RFC 2782,
         February 2000.

   [6]   Devarapalli, V., " Mobile IPv6 Operation with IKEv2 and the
         revised IPsec Architecture", Internet-Draft draft-ietf-mip6-
         ikev2-ipsec-04, October 2005.

   [7]   Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
         RFC 4306, December 2005.

   [8]   Johnson, D., and Deering, S., "Reserved IPv6 Subnet Anycast
         Addresses", RFC 2526, March 1999

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

13.2. Informative References

   [10]  Manner, J., Kojo, M. "Mobility Related Terminology", RFC
         3753, June 2004.

   [11]  Aura, T., "Cryptographically Generated Addresses (CGA)", RFC
         3972, March 2005.

   [12]  Narten, T., Draves, R., Krishnan, S., "Privacy Extensions
         for Stateless Address Autoconfiguration in IPv6", Internet-
         Draft draft-ietf-ipv6-privacy-addrs-v2-04, May 2005.





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   [13]  Droms, R., Ed., "DNS Configuration options for Dynamic Host
         Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
         December 2003.

   [14]  Giaretta, G., Ed. "Goals for AAA-HA interface", Internet-
         Draft draft-ietf-mip6-aaa-ha-goals-01, February 2006.

   [15]  Koodli, R., Devarapalli, V., Perkins, C., Flinck, H.,
         "Solutions for IP Address Location Privacy in the presence
         of IP Mobility", Internet-Draft, draft-koodli-mip6-location-
         privacy-solutions-00, February 2005.

   [16]  P. Vixie, Ed., S. Thomson, Y. Rekhter, and J. Bound.
         "Dynamic Updates in the Domain Name System (DNS UPDATE)",
         RFC 2136, April 1997.

   [17]  Chowdhury, K., Yegin, A., Choi, J., "MIP6-bootstrapping via
         DHCPv6 for the Integrated Scenario", Internet-Draft, draft-
         ietf-mip6-bootstrapping-integrated-dhc-00, October 2005.

   [18]  Arends, R., Austein, R., Larson, M., Massey, D., Rose, S.,
         "DNS Security Introduction and Requirements", RFC 4033,
         March 2005.

   [19]  Vixie, P., Gudmundsson, O., Eastlake 3rd, D., Wellington,
         B., "Secret Key Transaction Authentication for DNS (TSIG)",
         RFC 2845, May 2000.

   [20]  Eastlake 3rd, D., " Secret Key Establishment for DNS (TKEY
         RR)", RFC 2930, September 2000.

   [21]  Nikander, P., Arkko, J.,  Aura, T., Montenegro, G.,
         Nordmark, E., "Mobile IP version 6 Route Optimization
         Security Design Background", Internet-Draft, draft-ietf-
         mip6-ro-sec-02, October 2004.

   [22]  Narten, T., Nordmark, E., Simpson, W., Soliman, H.,
         "Neighbor Discovery for IP version 6 (IPv6)", Internet-
         Draft, draft-ietf-ipv6-2461bis-05, October 2005.

   [23]  Adams, C., et al., "Internet X.509 Public Key Infrastructure
         Certificate Management Protocol (CMP)", RFC 4210, September
         2005.










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Authors' Addresses

   Gerardo Giaretta
   Telecom Italia
   via Reiss Romoli 274
   10148 Torino
   Italy

   Phone: +39 011 228 6904
   Email: gerardo.giaretta@telecomitalia.it



   James Kempf
   DoCoMo Labs USA
   181 Metro Drive
   Suite 300
   San Jose, CA, 95110
   USA

   Phone: +1 408 451 4711
   Email: kempf@docomolabs-usa.com



   Vijay Devarapalli
   Azaire Networks


   Email: vijay.devarapalli@azairenet.com























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