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

     MIP6 WG                                         G. Giaretta, Editor
     Internet Draft                                                Tilab
     Expires: April 21, 2006                                    J. Kempf
                                                         DoCoMo Labs USA
                                                          V. Devarapalli
                                                                   Nokia
                                                        October 21, 2005
     
     
     
                   Mobile IPv6 bootstrapping in split scenario
                    draft-ietf-mip6-bootstrapping-split-01.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 aware will be disclosed, in accordance with Section 6 of
        BCP 79.
     
        Internet-Drafts are working documents of the Internet Engineering
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        This Internet-Draft will expire on April 21, 2006.
     
     Copyright Notice
     
        Copyright (C) The Internet Society (2005).  All Rights Reserved.
     
     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
           5.2. IPsec Security Associations setup........................13
           5.3. Home Address assignment..................................13
              5.3.1. Home Address assignment by the Home Agent...........13
              5.3.2. Home Address auto-configuration by the Mobile Node..13
           5.4. Authorization and Authentication with MSA................15
        6. Home Address registration in the DNS..........................17
        7. Summary of Bootstrapping Protocol Flow........................19
        8. Option and Attribute Format...................................21
           8.1. DNS Update mobility option...............................21
           8.2. MIP6_HOME_PREFIX attribute...............................22
        9. Security Considerations.......................................23
           9.1. HA Address Discovery.....................................23
           9.2. Home Address Assignment through IKEv2....................24
           9.3. SA Establishment Using EAP Through IKEv2.................25
           9.4. Back End Security Between the HA and AAA Server..........25
           9.5. Dynamic DNS Update.......................................25
        10. IANA Considerations..........................................27
        11. Contributors.................................................28
        12. Acknowledgments..............................................29
        13. References...................................................30
           13.1. Normative References....................................30
           13.2. Informative References..................................30
        Authors' Addresses...............................................32
        Intellectual Property Statement..................................33
        Disclaimer of Validity...........................................33
        Copyright Statement..............................................33
        Acknowledgment...................................................33
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
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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 MIPv6
        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 MNs 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 host 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 [8]. The following
        additional terms are used here:
     
        ASA
            Access Service Authorizer. A network operator that
            authenticates a mobile host and establishes the mobile host'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 host 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 draft [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 be also 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 MN for mobility service. If,
        instead, a PKI is used, the MN and HA exchange certificates and
        there is no AAA server involved. This is conceptually similar to
        Figure 1, since the MSP == MSA, except the HA 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. MIPv6 requires that a Mobile
           Node and its Home Agent share an IPsec SA in order to protect
           binding updates and other MIPv6 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  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 draft also
           allows the Mobile Node to auto-configure its Home Address based
           on stateless auto-configuration ([20]), Cryptographically
           Generated Addresses ([9]) or privacy addresses ([10]).
     
        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
        an address for a node prior to starting IP traffic with it. The
     
     
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        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
        [11]. 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 [15] 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] describes also 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, 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, if
        there is room in the SRV reply.
     
     
     
     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
        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
        IKEv2 authentication is done 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.
     
     
     
     5.3. 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
     
     
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        Generated Addresses (CGAs) [9] or based on the privacy extensions
        for stateless autoconfiguration [10]. 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 deployment, 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
        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 IP6_INTERNAL_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
     
     
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        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
        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
     
     
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        be explicitly authorized based on the user's profile. As an
        example, the Home Agent might not be aware if the mobility service
        can be granted at a particular time of the day or if 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.
     
        The definition of this backend communication is out of the scope
        of this document. In [12] 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 of DNS update 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 update for the
        Mobile Node. For this purpose the Mobile Node MAY include a new
        mobility option, the DNS Update option, with the flag R not set in
        the Binding Update. 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 [14]. 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
        domain. 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
        [14]. The detailed description of the communication between Home
        Agent and AAA is out of the scope of this draft. More details are
        provided in [12].
     
        A mechanism to remove stale DNS entries is needed. A DNS entry
        becomes stale when the related Home Address is no more used by the
        Mobile Node. To remove a DNS entry, the MN includes the DNS Update
        mobility option, with the flag R set in the Binding Update. 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 [14]. 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).
     
        This approach does not work if the Mobile Node stops using the
        Home Address without sending a Binding Update message (e.g. in
        case of crash). In this case, an additional mechanism to trigger
        the DNS entry removal is needed. For this purpose, the Home Agent
        has a timer related to the DNS entry of the Mobile Node. This
        timer is initialized when the Mobile Node sends a Binding Update
        with R==0 (i.e. when the MN asks the Home Agent to bind the FQDN
        to the Home Address). The initial value of this timer is
        configurable by the network operator.
     
        If the Home Agent receives a Binding Update with R==1, it removes
        the DNS entry as described in the previous paragraph and removes
        the timer associated to that entry. If the timer expires without
        receiving a Binding Update with R==1, the HA checks the Binding
        Cache. If there is an existing Binding Cache entry for the HoA,
        the HA does not remove the DNS entry and re-initialize the timer.
        If there is not a Binding Cache entry, it sends a Neighbor
        Solicitation message to check if the MN is at home and is using
        the HoA. If the HA gets a Neighbor Advertisement message, it does
        not remove the DNS entry and re-initialize the timer. If it does
        not receive a NA, it removes the DNS entry and the timer
        associated to it.
     
     
     
     
     
     
     
     
     
     
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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 3.
     
            +----+                  +----+              +-----+
            | MN |                  | HA |              | DNS |
            +----+                  +----+              +-----+
     
                   IKEv2 exchange
                (HoA configuration)
               <======================>
     
               BU (DNS update option)
               ----------------------->
                                             DNS update
                                       <------------------->
                BU (DNS update option)
               <-----------------------
     
     
                     Figure 3 - Dynamic DNS update by the HA
     
     
     
        Figure 4 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)
                                   <-------------->
              BU (DNS update option)
            <-----------------------
     
     
                     Figure 4 - 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 4.
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
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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 MN is requesting the HA to remove the DNS
           entry identified by the FQDN specified in this option and the
           HoA of the MN. If not set, the MN 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             |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |                                                               |
         |                        home prefix                            |
         |                                                               |
         |                                                               |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         | Prefix Length |
         +-+-+-+-+-+-+-+-+
     
     
        o  Reserved (1 bit) - This bit MUST be set to zero and MUST be
           ignored on receipt.
     
        o  Attribute Type (7 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  Home Prefix (16 octets) - The prefix of the home link through
           which the Mobile Node must auto-configure its Home Address.
     
        o  Prefix Length (1 octet) - The length of the home prefix
           specified in the field 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 [16] or TSIG/TKEY [17] [18] 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 MN'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 [15], 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 autoconfigure an address.
     
        RFC 3775 [2] and 3776 [3] require that a Home Agent check
        authorization on 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 autoconfigured, 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 [12] 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 [19] 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 [16]
        or TSIG/TKEY [17][18]. 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 [12] 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
        MN 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 [12] 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.
     
        The design team members can be reached at:
     
        Gerardo Giaretta  gerardo.giaretta@tilab.com
     
        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 vijayd@iprg.nokia.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,
        Basavaraj Patil, Jari Arkko, Kilian Weniger 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-
              03, July 2005.
     
        [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-03, September 2005.
     
        [7]   Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
              Internet-Draft draft-ietf-ipsec-ikev2-17, October 2004
     
     13.2. Informative References
     
        [8]   Manner, J., Kojo, M. "Mobility Related Terminology", RFC
              3753, June 2004.
     
        [9]   Aura, T., "Cryptographically Generated Addresses (CGA)", RFC
              3972, March 2005.
     
        [10]  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.
     
        [11]  Droms, R., Ed., "DNS Configuration options for Dynamic Host
              Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
              December 2003.
     
        [12]  Giaretta, G., Ed. "Goals for AAA-HA interface", Internet-
              Draft draft-ietf-mip6-aaa-ha-goals-00, April 2005.
     
     
     
     
     
     
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        [13]  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.
     
        [14]  P. Vixie, Ed., S. Thomson, Y. Rekhter, and J. Bound.
              "Dynamic Updates in the Domain Name System (DNS UPDATE)",
              RFC 2136, April 1997.
     
        [15]  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.
     
        [16]  Arends, R., Austein, R., Larson, M., Massey, D., Rose, S.,
              "DNS Security Introduction and Requirements", RFC 4033,
              March 2005.
     
        [17]  Vixie, P., Gudmundsson, O., Eastlake 3rd, D., Wellington,
              B., "Secret Key Transaction Authentication for DNS (TSIG)",
              RFC 2845, May 2000.
     
        [18]  Eastlake 3rd, D., " Secret Key Establishment for DNS (TKEY
              RR)", RFC 2930, September 2000.
     
        [19]  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.
     
        [20]  Narten, T., Nordmark, E., Simpson, W., Soliman, H.,
              "Neighbor Discovery for IP version 6 (IPv6)"`, Internet-
              Draft, draft-ietf-ipv6-2461bis-03, May 2005.
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
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     Authors' Addresses
     
        Gerardo Giaretta
        Telecom Italia Lab
        via Reiss Romoli 274
        10148 Torino
        Italy
     
        Phone: +39 011 228 6904
        Email: gerardo.giaretta@tilab.com
     
     
     
        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
        Nokia Research Center
        313 Fairchild Drive
        Mountain View, CA  94043
        USA
     
        Email: vijay.devarapalli@nokia.com
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
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