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Versions: 00 01 02 03 04 05 RFC 4640

MIP6                                             Alpesh. Patel, (Editor)
Internet-Draft                                             cisco Systems
Expires: January 7, 2005                                    July 9, 2004



            Problem Statement for bootstrapping Mobile IPv6
                    draft-ietf-mip6-bootstrap-ps-00


Status of this Memo


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   This Internet-Draft will expire on January 7, 2005.


Copyright Notice


   Copyright (C) The Internet Society (2004).  All Rights Reserved.


Abstract


   A mobile node needs home address, home agent address and security
   association with home agent to register with the home agent.  The
   process of obtaining this information is called bootstrapping.  This
   document This document defines the problem for how the mobile can be
   bootstrapped in various deployment scenarios.









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Table of Contents


   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1   Overview of the Problem  . . . . . . . . . . . . . . . . .  3
     1.2   What is Bootstrapping? . . . . . . . . . . . . . . . . . .  4
     1.3   Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Assumptions  . . . . . . . . . . . . . . . . . . . . . . . . .  6
   3.  Design Goals . . . . . . . . . . . . . . . . . . . . . . . . .  7
   4.  Non-Goals  . . . . . . . . . . . . . . . . . . . . . . . . . .  8
   5.  Motivation for bootstrapping . . . . . . . . . . . . . . . . .  9
     5.1   Addressing . . . . . . . . . . . . . . . . . . . . . . . .  9
       5.1.1   Dynamic Home Address Assignment  . . . . . . . . . . .  9
       5.1.2   Dynamic Home Agent Assignment  . . . . . . . . . . . . 10
       5.1.3   Management requirements  . . . . . . . . . . . . . . . 11
     5.2   Security Infrastructure  . . . . . . . . . . . . . . . . . 11
       5.2.1   Integration with AAA Infrastructure  . . . . . . . . . 11
       5.2.2   Opportunistic or Local Discovery . . . . . . . . . . . 12
     5.3   Topology Change  . . . . . . . . . . . . . . . . . . . . . 12
       5.3.1   Dormant Mode Mobile Nodes  . . . . . . . . . . . . . . 12
   6.  Network Access and Mobility services . . . . . . . . . . . . . 13
   7.  Deployment scenarios . . . . . . . . . . . . . . . . . . . . . 15
     7.1   Mobility Service Subscription Scenario . . . . . . . . . . 15
     7.2   Integrated ASP network scenario  . . . . . . . . . . . . . 15
     7.3   Third party MSP scenario . . . . . . . . . . . . . . . . . 16
     7.4   Infrastructure-less scenario . . . . . . . . . . . . . . . 17
   8.  Parameters for authentication  . . . . . . . . . . . . . . . . 18
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 20
   10.   Contributors . . . . . . . . . . . . . . . . . . . . . . . . 22
   11.   Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . 23
   12.   References . . . . . . . . . . . . . . . . . . . . . . . . . 24
   12.1  Normative References . . . . . . . . . . . . . . . . . . . . 24
   12.2  Informative References . . . . . . . . . . . . . . . . . . . 24
       Editor's Address . . . . . . . . . . . . . . . . . . . . . . . 25
       Intellectual Property and Copyright Statements . . . . . . . . 26


















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1.  Introduction


   Mobile IPv6 [2] specifies mobility support based on the assumption
   that a mobile node has a trust relationship with an entity called the
   home agent.  Once the home agent address has been learned either via
   manual configuration or via anycast discovery mechanisms, Mobile IPv6
   signaling messages between the mobile node and the home agent are
   secured with IPsec.  The requirements for this security architecture
   are created with [2] and the details of this procedure are described
   in [3].


   In [2] there is an implicit requirement that the MN be provisioned
   with enough information that will permit it to register successfully
   with its home agent.  Requirement to have this information statically
   provisioned creates practical deployment issues.


   This document serves to define the problem of bootstrapping.
   Bootstrapping is defined as obtaining enough information at the
   mobile node, so that the mobile node can successfully register with
   an appropriate home agent.


   The requirements for bootstrapping could consider various scenarios/
   network deployment issues.  It is the basic assumption of this
   document that certain minimal parameters (seed information) is
   available to the mobile node to aid in bootstrapping.  The exact seed
   information available differs depending on the deployment scenario.
   This document defines/describes various deployment scenarios and
   provides for a set of minimal parameters that are available in each
   deployment scenario.


   This document stops short of suggesting the various solutions to
   obtaining information on the mobile node.  Such details will be
   available from separate documents.


1.1  Overview of the Problem


   Mobile IPv6 [2] expects the mobile node to have a static home
   address, home agent address (or anycast address and do dynamic home
   agent discovery of Home Agent using ICMP messages) and a security
   association with a home agent (multiple home agents on the home
   network if dynamic home agent discovery is in use and multiple home
   agents are deployed.)


   This static provisioning of information has various problems as
   discussed in Section 5.


   The aim of this draft is to:





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   o  Define bootstrapping.
   o  Identify sample deployment scenarios where MIPv6 will be deployed,
      taking into account the relationship between the subscriber and
      the service provider.
   o  Identify the minimal set of information required on the Mobile
      Node (and/or) in the network in order for the the mobile node to
      obtain address and security credentials, to register with the home
      agent.


1.2  What is Bootstrapping?



   Bootstrapping is defined as obtaining enough information at the
   mobile node, so that the mobile node can successfully register with
   an appropriate home agent.  Specifically, this means obtaining the
   home agent address, home address and security credentials for the
   mobile node and home agent to authenticate and mutually construct
   security credentials for Mobile IPv6 without requiring
   preconfiguration.


   Typically, bootstrapping happens when a mobile node does not have all
   the information it needs to setup Mobile IPv6 service.  This
   includes, but is not limited to MN not having any information when it
   boots up for the first time (out of the box), it does not retain any
   information during reboots, is instructed by the Home Agent (via some
   form of signalling) to do so etc.


   Also, in certain scenarios, after the MN bootstraps for the first
   time (out of the box), subsequent bootstrapping is implementation
   dependent.  For instance, MN may bootstrap everytime it boots,
   bootstrap everytime on prefix change, bootstrap periodically to
   anchor to an optimal (distance, load etc) HA, etc.


1.3  Terminology



   For a complete introduction to terminology, please refer to [4].


   General mobility terminology can be found in [4].  The following
   additional terms are used here:


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


   IASP
      Integrated Internet Service Provider.  A service provider
      providing both network access and mobility.  Referred to as IASP




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      or ASP/MSP in the document.


   MSP
      Mobility Service Provider.  A service provider that provides
      Mobile IPv6 service.  Granting such service requires
      authentication.














































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2.  Assumptions


   o  A basic assumption in the Mobile IPv6 RFC [2] is that there is a
      trust relationship between the mobile node and MSP.  This trust
      relationship can be direct, or indirect through, for instance, an
      ASP that has a contract with the MSP.  This trust relationship can
      be used to bootstrap the MN.


      One typical way of verifying the trust relationship is using
      authentication, authorization, and accounting (AAA).  In this
      document, two distinct types of AAA are considered:


      AAA for Network Access
         This functionality provides authentication and authorization to
         access the network (obtain address and send/receive packets).


      AAA for Mobility Service
         This functionality provides authentication and authorization
         for mobility services.


      These functionalities may be implemented in a single entity or in
      different entities, depending on the service models described in
      Section 6 or deployment scenarios as described in Section 7.


   o  Yet another assumption is that some identifier, such as NAI, as
      defined in [7] or [8] is provisioned on the MN which permits the
      MN to identify itself to the ASP and ASP.

























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3.  Design Goals


   A solution to the bootstrapping problem has the following design
   goals:


   o  The following information must be available at the end of
      bootstrapping, to enable the MN to register with the HA.


      *  MN's home address
      *  MN's home agent address
      *  IPsec SA between MN and HA or IKE pre-shared secret between MN
         and HA.
   o  The bootstrapping procedure can be triggered at any time.
   o  Subsequent protocol interaction (for example updating the IPsec
      SA) can be executed between the MN and the HA itself without
      involving the infrastructure that was used during bootstrapping.
   o  Solutions to the bootstrapping problem should not exclude storage
      of user-specific information on entities other than the home
      agent.
   o  Configuration information which is exchanged between the mobile
      node and the home agent must be secured using integrity and replay
      protection.  Confidentiality protection SHOULD be provided if
      necessary.
   o  All feasible deployment scenarios, along with the relevant
      authentication/authorization models must be considered.



























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4.  Non-Goals


   This following issues are clearly outside the scope of bootstrapping:


   o  Home prefix renumbering is not explicity supported as part of
      bootstrapping.  If the MN executes the bootstrap procedures
      everytime it powers-on (as opposed to caching state information
      from previous bootstrap process), then home network renumbering is
      taken care of automatically.


   o  Bootstrapping in the absence of a trust relationship between MN
      and any provider, is not considered.  The reason for this is
      described in  Section 9.







































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5.  Motivation for bootstrapping


5.1  Addressing


   The default bootstrapping described in the Mobile IPv6 base
   specification [2] has a tight binding to the home addresses and home
   agent addresses.



   In this section, we discuss the problems caused by the currently
   tight binding to home addresses and home agent addresses.


5.1.1  Dynamic Home Address Assignment


   While it is possible for the home address to be dynamically assigned,
   the HA cannot verify that the MN is authorized to use a particular
   address.  As a result, static home address assignment is really the
   only home address configuration technique compatible with the current
   specification.


   However, support for dynamic home address assignment would be
   desirable for the following reasons:


   DHCP-based address assignment


      Some ASPs may want to use DHCPv6 from the home network to
      configure home addresses.



   Recovery from a duplicate address collision


      It may be necessary to recover from a collision of addresses on
      the home network.



   Addressing privacy


      It may be desirable to establish randomly generated addresses as
      in RFC 3041 and use them for a short period of time.
      Unfortunately, current protocols make it possible to use such
      addresses only from the visited network.  As a result, these
      addresses can not be used for communications lasting longer than
      the attachment to a particular visited network.









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   Ease of deployment


      In order to make deployment of Mobile IPv6 easy, it would be
      desirable to free users and administrators from the task of
      allocating home addresses and specifying them in the security
      policy database.


      This is consistent with the general IPv6 design goal of using
      autoconfiguration whereever possible.


   Prefix changes in the home network


      The Mobile IPv6 specification contains support for a mobile node
      to autoconfigure a home address based on its discovery of prefix
      information on the home subnet [2].  Autoconfiguration in case of
      network renumbering is done by replacing the existing network
      prefix with the new network prefix.


      Subsequently, the MN needs to update the mobility binding in the
      HA to register the newly configured Home Address.  However, the MN
      may not be able to register the newly configured address with the
      HA if a security association related to that reconfigured Home
      Address does not exist in the MN and the HA.  This situation is
      not handled in the current MIPv6 specification [2].


5.1.2  Dynamic Home Agent Assignment


   Currently, the address of the home agent is specified in the security
   policy database.  Support for multiple home agents requires the
   configuration of multiple security policy database entries.


   However, support for dynamic home agent assignment would be desirable
   for the following reasons:


   Home agent discovery


      The Mobile IPv6 specification contains support for a mobile node
      to autoconfigure a home agent address based on a discovery
      protocol [2].


   Independent network management


      An ASP may want to dynamically assign home agents in different
      subnets, that is, not require that a roaming mobile node have a
      fixed home subnet.







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   Local home agents


      The mobile node's home ASP may want to allow a local roaming
      partner ASP to assign a local home agent for the mobile node.
      This is useful both from the point of view of communications
      efficiency, and has also been mentioned as one approach to support
      location privacy.


   Ease of deployment


      MSP may want to allow "opportunistic" discovery and utilization of
      its mobility services without any prearranged contact.  These
      scenarios will require dynamic home address assignment.


5.1.3  Management requirements


   As described earlier, new addresses invalidate configured security
   policy databases and authorization tables.  Regardless of the
   specific protocols used, there is a need for either an automatic
   system for updating the security policy entries, or manual
   configuration.  These requirements apply to both home agents and
   mobile nodes, but it can not be expected that mobile node users are
   capable of performing the required tasks.


5.2  Security Infrastructure


5.2.1  Integration with AAA Infrastructure


   The current IKEv1-based dynamic key exchange protocol described in
   [3] has no integration with backend authentication, authorization and
   accounting techniques unless the authentication credentials and trust
   relationships use certificates or pre-shared secrets.


   Using certificates may require the ASP to deploy a PKI, which may not
   be possible or desirable in certain circumstances.  Where a
   traditional AAA infrastructure is used, the home agent is not able to
   leverage authentication and authorization information established
   between the mobile node, the foreign AAA server, and the home AAA
   server when the mobile node gains access to the foreign network, in
   order to authenticate the mobile node's identity and determine if the
   mobile node is authorized for mobility service.


   The lack of connection to the AAA infrastructure also means the home
   agent does not know where to issue accounting records at appropriate
   times during the mobile node's session, as determined by the business
   relationship between the home ASP and the mobile node's owner.





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   Presumably, some backend AAA protocol between the home agent and home
   AAA could be utilized, but IKEv1 does not contain support for
   exchanging full AAA credentials with the mobile node.  It is
   worthwhile to note that IKEv2 provides this feature.


5.2.2  Opportunistic or Local Discovery


   The home agent discovery protocol does not support an "opportunistic"
   or local discovery mechanisms in an ASP's local access network.  It
   is expected that the mobile node must know the prefix of the home
   subnet in order to be able to discover a home agent.  It must either
   obtain that information through prefix update or have it statically
   configured.  A more typical pattern for interdomain service discovery
   in the Internet is that the client (mobile node in this case) knows
   the domain name of the service, and uses DNS in some manner to find
   the server in the other domain.  For local service discovery, DHCP is
   typically used.


5.3  Topology Change


5.3.1  Dormant Mode Mobile Nodes


   The description of the protocol to push prefix information to mobile
   nodes in Section 10.6 in [2] has an implicit assumption that the
   mobile node is active and taking IP traffic.  In fact, many, if not
   most, mobile devices will be in a low power "dormant mode" to save
   battery power, or even switched off, so they will miss any
   propagation of prefix information.  As a practical matter, if this
   protocol is used, an ASP will need to keep the old prefix around and
   handle any queries to the old home agent anycast address on the old
   subnet, whereby the mobile node asks for a new home agent as
   described in Section 11.4, until all mobile nodes are accounted for.
   Even then, since some mobile nodes are likely to be turned off for
   long periods, some owners would need to be contacted by other means,
   reducing the utility of the protocol.


   Bootstrapping does not explicitly try to solve this problem of home
   network renumbering when MN is in dormant mode.  If the MN can
   configure itself after it 'comes back on' by reinitiating the
   bootstrapping process, then network renumbering problem is fixed as a
   side-effect.











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6.  Network Access and Mobility services


   This section defines some terms as it pertains to authentication and
   practical network deployment/roaming scenarios.  This description
   lays the ground work for Section 7.  The focus is on the 'service'
   model since, ultimately, it is the provider providing the service
   that wants to authenticate the mobile (and vice-versa for mutual
   authentication between provider and the user of the service).


   Network access service enables a host to send and receive IP packets
   on the Internet or an intranet.  IP address configuration and IP
   packet forwarding capabilities are required to deliver this service.
   A network operator providing this service is called an access service
   provider (ASP).  An ASP can be a commercial ASP, the IT department of
   an enterprise network, or the maintainer of a home (residential)
   network.


   When the network service requires authentication, the concept of home
   ASP and serving ASP comes into the picture.  Home ASP is the provider
   with whom the user has an account.  Therefore, when the user directly
   connects to the home ASP network, the ASP can perform authentication
   without relying on any other service provider.  On the other hand,
   when the user is roaming on the Internet, it may connect to another
   ASP network that has a roaming agreement with the home ASP.  That ASP
   is called serving ASP.  The serving ASP cannot authenticate a roaming
   user on its own, for that it needs to contact the home ASP.


   A host does not always have to use an IP address from one of its home
   ASP prefixes.  It may be configured with one from the serving ASP's
   prefixes.  In fact, the home ASP may not even have a physical access
   network, in which case it could be identified as a virtual operator.


   Another service is called Mobile IPv6 service, which enables a host
   to maintain its IP reachability despite changing its network
   attachment points (subnets).  Providing Mobile IPv6 service involves
   setting up a home agent on a subnet that acts as a Mobile IPv6 home
   link.  Home agent's responsibility include tunneling host's IP
   packets between the home link and its current point-of attachment.  A
   network operator providing this service is called a mobility service
   provider (MSP).  Mobile IPv6 requires authentication between the host
   and the home agent.  The MSP that maintains an account for the user
   is called a home MSP.  A home MSP can authenticate its users without
   relying on any other service provider.  Conceptually, the user may be
   receiving the Mobile IP service from another MSP that has a roaming
   agreement with the home MSP.  Such a service provider is called
   serving MSP.  A serving MSP needs to contact the home MSP in order to
   authenticate the user before providing the mobility service.





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   A host may authenticate with a MSP based on the some kind of AAA
   association with the ASP (typically the home ASP or through the home
   ASP).


   A host does not always have to use a Mobile IPv6 home address from
   one of its home MSP prefixes.  It may be configured with one from the
   serving MSP's prefixes.  In fact, the home MSP may not even have a
   physical access network, in which case it could be identified as a
   virtual operator.


   Network access and Mobile IPv6 are two distinct services.  A host can
   choose to have only network access service, or both network access
   and Mobile IPv6 services at the same time.  Only having Mobile IPv6
   service is not possible, since the Mobile IPv6 protocol requires
   ability to send and receive IPv6 packets.  Even when both services
   are received by a host, the service providers involved might vary.
   All combinations are possible with respect to the choice of ASPs and
   MSPs:


   o  The serving ASP might be the home ASP.  Similarly, the serving MSP
      might be the home MSP.
   o  The home ASP and the home MSP may be the same operator, or not.
      When they are the same, the same set of credentials may be used
      for both services.
   o  The serving ASP and the serving MSP may be the same operator, or
      not.
   o  It is possible that serving ASP and home MSP are the same
      operator.


   Similarly the home ASP and serving MSP may be the same.


   These entities and possible combinations must be taken into
   consideration when solving the Mobile IPv6 bootstraping problem.
   They impact home agent discovery, home address configuration, and
   mobile node to home agent authentication aspects.

















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7.  Deployment scenarios


   This section describes the various network deployment scenarios.  The
   various combinations of service providers as described in Section 6
   are considered.


   For each scenario, the underlying assumptions are described.  The
   basic assumption is that there is a trust relationship between mobile
   user and the MSP.  Typically, this trust relationship is between the
   mobile user and AAA in the MSP network.  Seed information needed to
   bootstrap the mobile node is considered in two cases (i) AAA
   authentication is mandatory for network access "&amp" (ii) AAA
   authentication is not part of network access.  The seed information
   is described further in Section 8.


7.1  Mobility Service Subscription Scenario


   Many commercial deployments are based on the assumption that mobile
   nodes have a subscription with a service provider.  In particular, in
   this scenario the MN has a subscription with an MSP, called the home
   MSP, for Mobile IPv6 service.  As stated in Section 6, the MSP is
   responsible of setting up a home agent on a subnet that acts as a
   Mobile IPv6 home link.  As a consequence, the home MSP should
   explicitly authorize and control the whole bootstrapping procedure.


   Since the MN is assumed to have a pre-established trust relationship
   with its home provider, it must be configured with an identity and
   credentials, for instance an NAI and a shared secret by some
   out-of-band means before bootstrapping, for example by manual
   configuration.


   In order to guarantee ubiquitous service, the MN should be able to
   bootstrap MIPv6 operations with its home MSP from any possible access
   location, such as an open network or a network managed by an ASP,
   that may be different from the MSP and may not have any
   pre-established trust relationship with it.


7.2  Integrated ASP network scenario


   In this scenario, the ASP and MSP are the same ASP.  MN shares
   security credentials for access to the network and these credentials
   can be used to bootstrap MIPv6.  This bootstrapping can be done
   during the same phase as access authentication/authorization or at a
   later time (probably based on some state created during access
   authentication/authorization).


   Figure 1 describes an example AAA design for integrated ASP scenario.





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                     +----------------------------+
                     | IASP(ASP+MSP)              |
        +----+    +-----+         +----+          |
        | MN |--- | NAS |         | HA |          |
        +----+    +-----+         +----+          |
                     | \            \             |
                     |  \ +------+   \ +-------+  |
                     |   -|AAA-NA|    -|AAA-MIP|  |
                     |    +------+     +-------+  |
                     +----------------------------+


             NAS: Network Access Server
             AAA-NA: AAA for network access
             AAA-MIP: AAA for Mobile IP service


                    Figure 1: Integrated ASP network



7.3  Third party MSP scenario


   Mobility service has traditionally been provided by the same entity
   that authenticates and authorizes the subscriber for network access.
   This is certainly the only model support by the base Mobile IPv6
   specification.


   In the 3rd party mobility service provider scenario, the subscription
   for mobility service is made with one entity (home MSP for instance a
   corporate network), but the actual mobility service is provided by
   yet another entity (such as an operator specializing on this service,
   the serving MSP).  These two entities have a trust relationship.
   Transitive trust among the mobile node and these two entities may be
   used to assure the participants that they are dealing with, are
   trustworthy peers.


   This arrangement is similar to the visited - home operator roaming
   arrangement for network access.


   Figure 2 describes an example network for third party MSP scenario.














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                     +--------------+   +--------+
                     |              |   |Serving |
                     | ASP          |   | MSP    |
        +----+    +-----+           |   | +----+ |
        | MN |--- | NAS |           |   | | HA | |  +-------------------+
        +----+    +-----+           |===| +----+ |  | Home MSP          |
                     | \            |   |    \   |  | (e.g.corporate NW)|
                     |  \ +------+  |   |     \     | +-------+         |
                     |   -|AAA-NA|  |   |      -------|AAA-MIP|         |
                     |    +------+  |   |        |  | +-------+         |
                     +------------  +   +--------+  +-------------------+



                   Figure 2: Third Party MSP network



7.4  Infrastructure-less scenario


   Infrastructure refers to network entities like AAA, PKI, HLR etc.
   Infrastructure-less implies that there is no dependency on any
   elements in the network with which the user has any form of trust
   relationship.


   In such a scenario, there is absolutely no relationship between host
   and infrastructure.


   A good example of infrastructure-less environment for MIP6
   bootstrapping is the IETF network at IETF meetings.  It is possible
   that there could be MIP6 service available on this network (i.e a
   MIPv6 HA).  However there is not really any AAA infrastructure or for
   that matter any trust relationship that a user attending the meeting
   has with any entity in the network.


   This specific scenario is not supported in this document.  The reason
   for this is described in Section 9.

















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8.  Parameters for authentication


   The following is a list of parameters that are used as the seed for
   the bootstrapping procedure.  The parameters vary depending on
   whether authentication for network access is independent of
   authentication for mobility services or not.  Authentication for
   network access is always independent of authentication for mobility
   services if different client identities are used for network access
   and mobility services.


   o  Parameter Set 1


      In this case, authentication for network access is independent of
      authentication for mobility services.


      If the home agent address is not known to the mobile node the
      following parameter is needed for discovering the home agent
      address:


      *  The domain name or FQDN of the home agent


      This parameter may be derived in various ways such as (but not
      limited to) static configuration, use of the domain name from the
      network access NAI (even if AAA for network access is not
      otherwise used) or use of the domain name of the serving ASP where
      the domain name may be obtained via DHCP in the serving ASP.


      If the home agent address is not known but the home subnet prefix
      is known, Dynamic Home Agent Address Discovery of Mobile IPv6 may
      be used for discovering the home agent address and the above
      parameter may not be used.


      When the home agent address is known to the mobile node, the
      following parameter is needed for performing mutual authentication
      between the mobile node and the home agent by using IKE:


      *  IKE credentials(*)


      In the case where the home agent does not have the entire set of
      IKE credentials, the home agent may communicate with other entity
      (e.g., a AAA server) to perform mutual authentication in IKE.  In
      such a case, the IKE credentials include the credentials used
      between the mobile node and the other entity.  In the case where a
      AAA protocol is used for the communication between the home agent
      and the other entity during the IKE procedure, AAA for Mobile IPv6
      service may be involved in IKE.






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   o  Parameter Set 2


      In this case, some dependency exists between authentication for
      network access and authentication for mobility services in that a
      security association that is established as a result of
      authentication for network access is re-used for authentication
      for mobility services.


      All required information including IKE credentials are
      bootstrapped from the following parameter:


      *  Network access credentials(*)



   (*) A pair of a NAI and a pre-shared secret is an example set of
   credentials.  A pair of an NAI and a public key, which may be
   provided as a digital certificate, is another example set of
   credentials.


































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9.  Security Considerations


   The bootstrapping procedure needs to create a security association
   that matches the requirements set for its use.  Mobile IPv6 base
   specification expects strong, mutual authentication and trust
   relationship between the mobile node and home agent.  This is
   necessary, for instance, to ensure that fraudulent mobile nodes that
   flood other nodes with traffic [draft-ietf-mipv6-ro-sec] can not only
   be shut off from the service, but also tracked down.  The use of
   infrastructureless techniques does not satisfy these requirements, at
   least not without introducing additional routability tests to the
   Mobile IPv6 home registration procedure.


   Thus, the case of infrastructure-less network where there is
   absolutely no pre-mediated trust is kept outside of scope of this
   document.


   Another requirement is that the "ownership" to a particular home
   address must be authorized to at most one mobile node at a time.
   This implies that a Mobile IPv6 security association is always tied
   to zero or more such authorizations; these authorizations can either
   be created at the time the security association is created, or
   dynamically managed through, for instance, a First Come First Served
   allocation policy.


   Where an automatic bootstrap process is used, it becomes necessary to
   associate a lifetime with all the parameters which are bootstrapped.
   Otherwise a large number of unused security associations would have
   to be stored by the participating nodes, either by accident or
   through malicious behaviour or the mobile node will have stale
   information.


   The specific mean of verifying the security association is not
   defined in this document, but it can be, for example a set of IKE
   credentials, an IPsec security association, a username-password -like
   association or digital signature constructed by a certified key.


   The bootstrap process itself may have vulnerabilities.  The following
   issues need to be addressed:


   o  Mutual authentication and trust relationship between the mobile
      node and the entity handling the bootstrap process.  Refer to
      Section 7.15 in [9] and [10] for further information.
   o  Cryptographic separation and naming of session keys used for
      multiple purposes, such as network access authentication and
      mobility service.
   o  Ensuring that key lifetimes are not exceeded.





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   o  Binding security associations to specific home agent and address
      allocations.
   o  Support of multiple algorithms for the resulting security
      associations.
   o  Avoidance of denial-of-service vulnerabilities.















































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10.  Contributors


   This contribution is a joint effort of the problem statement design
   team of the Mobile IPv6 WG.  The contributors (alphabetical order)
   include Jari Arkko, Samita Chakrabarti, Kuntal Chowdhury, Vijay
   Devarapalli, Gopal Dommety, Gerardo Giaretta, James Kempf, Kent
   Leung, Yoshihiro Ohba, Hiroyuki Ohnishi, Basavaraj Patil, Hannes
   Tschofenig, Ryuji Wakikawa, Mayumi Yanagiya and Alper Yegin.












































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11.  Acknowledgments


   Special thanks to James Kempf and Jari Arkko for writing the initial
   version of the bootstrapping statement.
















































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12.  References


12.1  Normative References


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


   [2]  Johnson, D., Perkins, C. and J. Arkko, "Mobility Support in
        IPv6", RFC 3775, July 2003.


   [3]  Arkko, J., Devarapalli, V. and F. Dupont, "Using IPsec to
        Protect Mobile IPv6 Signaling between  Mobile Nodes and Home
        Agents", RFC 3776, July 2003.


   [4]  Manner, J. and M. Kojo, "Mobility Related Terminology",
        draft-ietf-seamoby-mobility-terminology-06 (work in progress),
        February 2004.


12.2  Informative References


   [5]   Giaretta, G., "MIPv6 Authorization and Configuration based on
         EAP", draft-giaretta-mip6-authorization-eap-00 (work in
         progress), February 2004.


   [6]   Kempf, J. and J. Arkko, "The Mobile IPv6 Bootstrapping
         Problem", draft-kempf-mip6-bootstrap-00 (work in progress),
         March 2004.


   [7]   Patel, A., Leung, K., Akthar, H., Khalil, M. and K. Chowdhury,
         "Network Access Identifier Option for Mobile IPv6",
         draft-ietf-mip6-nai-option-00 (work in progress), February
         2004.


   [8]   Calhoun, P. and C. Perkins, "Mobile IP Network Access
         Identifier Extension for IPv4", RFC 2794, March 2000.


   [9]   Levkowetz, Ed., H., "Extensible Authentication Protocol (EAP)",
         draft-ietf-eap-rfc2284bis-09 (work in progress), February 2004.


   [10]  Mariblanca, D., "EAP lower layer attributes for AAA protocols",
         draft-mariblanca-aaa-eap-lla-00.txt (work in progress), May
         2004.










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Editor's Address


   Alpesh Patel
   cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   USA


   Phone: +1 408 853 9580
   EMail: alpesh@cisco.com










































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