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Versions: 00 01 02 03 04 05 RFC 4640

MIP6                                                    A. Patel, Editor
Internet-Draft                                                     Cisco
Expires: September 16, 2005                               March 18, 2005


            Problem Statement for bootstrapping Mobile IPv6
                   draft-ietf-mip6-bootstrap-ps-02.txt

Status of this Memo

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   patent or other IPR claims of which I am aware have been disclosed,
   and any of which I become aware will be disclosed, in accordance with
   RFC 3668.

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   This Internet-Draft will expire on September 16, 2005.

Copyright Notice

   Copyright (C) The Internet Society (2005).  All Rights Reserved.

Abstract

   A mobile node needs at least the following information: a home
   address, home agent address and a security association with home
   agent to register with the home agent.  The process of obtaining this
   information is called bootstrapping.  This document discuss the
   issues involved with how the mobile node can be bootstrapped for
   Mobile IPv6 and various potential deployment scenarios for
   bootstrapping the mobile node.






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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  . . . . . . . . . . . . . . . . . . . . . . . . .  7
   3.  Design Goals . . . . . . . . . . . . . . . . . . . . . . . . .  8
   4.  Non-Goals  . . . . . . . . . . . . . . . . . . . . . . . . . .  9
   5.  Motivation for bootstrapping . . . . . . . . . . . . . . . . . 10
     5.1   Addressing . . . . . . . . . . . . . . . . . . . . . . . . 10
       5.1.1   Dynamic Home Address Assignment  . . . . . . . . . . . 10
       5.1.2   Dynamic Home Agent Assignment  . . . . . . . . . . . . 11
       5.1.3   Management requirements  . . . . . . . . . . . . . . . 12
     5.2   Security Infrastructure  . . . . . . . . . . . . . . . . . 12
       5.2.1   Integration with AAA Infrastructure  . . . . . . . . . 12
       5.2.2   "Opportunistic" or "Local" Discovery . . . . . . . . . 13
     5.3   Topology Change  . . . . . . . . . . . . . . . . . . . . . 13
       5.3.1   Dormant Mode Mobile Nodes  . . . . . . . . . . . . . . 13
   6.  Network Access and Mobility services . . . . . . . . . . . . . 14
   7.  Deployment scenarios . . . . . . . . . . . . . . . . . . . . . 16
     7.1   Mobility Service Subscription Scenario . . . . . . . . . . 16
     7.2   Integrated ASP network scenario  . . . . . . . . . . . . . 16
     7.3   Third party MSP scenario . . . . . . . . . . . . . . . . . 17
     7.4   Infrastructure-less scenario . . . . . . . . . . . . . . . 18
   8.  Parameters for authentication  . . . . . . . . . . . . . . . . 19
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 21
     9.1   Security Requirements of Mobile IPv6 . . . . . . . . . . . 21
     9.2   Threats to the Bootstrapping Process . . . . . . . . . . . 22
   10.   Contributors . . . . . . . . . . . . . . . . . . . . . . . . 23
   11.   Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . 24
   12.   References . . . . . . . . . . . . . . . . . . . . . . . . . 25
   12.1  Normative References . . . . . . . . . . . . . . . . . . . . 25
   12.2  Informative References . . . . . . . . . . . . . . . . . . . 25
       Author's Address . . . . . . . . . . . . . . . . . . . . . . . 26
       Intellectual Property and Copyright Statements . . . . . . . . 27















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1.  Introduction

   Mobile IPv6 [RFC3775] 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
   for example via manual configuration, via anycast discovery
   mechanisms, via DNS lookup; Mobile IPv6 signaling messages between
   the mobile node and the home agent are secured with IPsec or
   authentication protocol [I-D.ietf-mip6-mn-auth-protocol-02].  The
   requirements for this security architecture are created with
   [RFC3775] and the details of this procedure are described in
   [RFC3776].

   In [RFC3775] there is an implicit requirement that the MN be
   provisioned with enough information that will permit it to register
   successfully with its home agent.  However, having this information
   statically provisioned creates practical deployment issues.

   This document serves to define the problem of bootstrapping.
   Bootstrapping is defined as the process of the mobile node obtaining
   enough information, so that it 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 [RFC3775] 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.




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   The aim of this draft is to:

   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 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 the 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, the 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


   General mobility terminology can be found in
   [I-D.ietf-seamoby-mobility].  The following additional terms are used
   here:

   Trust relationship
      In the context of this draft, trust relationship means that two
      parties in question, typically the user of the mobile host and the
      mobility or access service provider, have some sort of prior
      contact in which the mobile host was provisioned with credentials.
      These credentials allow the mobile host to authenticate itself to



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      the mobility or access service authorizer and to prove its
      authorization to obtain service.

   Infrastructureless relationship
      In the context of this draft, an infrastructureless relationship
      is one in which the user of the mobile host and the mobility or
      access service provider have no previous contact and the mobile
      host is not required to supply credentials to authenticate and
      prove authorization for service.  Mobility and/or network access
      service is provided without any authentication or authorization.
      Infrastructureless in this context does not mean that there is no
      network infrastructure, such as would be the case for an ad hoc
      network.

   Credentials
      Data or mechanism used by a mobile host to authenticate itself to
      a mobility or access network service provider and prove
      authorization to receive service.  User name/passwords, one time
      password cards, public/private key pairs with certificates,
      biometric information, etc.  are some examples.

   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.

   Serving Network Access Provider
      A network operator that is the mobile host's ASP but not its ASA.
      The serving network accesss provider may or may not additionally
      provide mobility service.

   Home Network Access Provider
      A network operator that is both the mobile host's ASP and ASA.
      The home network access provider may or may not additionally
      provide mobility service (note that this is a slighlty different
      definition from RFC 3775).

   IASP
      Integrated Access Service Provider.  A service provider that
      provides both authorization for network access and also provides
      mobility service.

   MSA




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      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.

   Home Mobility Service Provider
      A MSP that both provides mobility service and authorizes it.

   Serving Mobility Service Provider
      A MSP that provides mobility service but depends on another
      service provider to authorize it.




































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2.  Assumptions

   o  A basic assumption in the Mobile IPv6 RFC [RFC3775] 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).
      infrastructure.  In this document, two distinct uses 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 [I-D.ietf-mip6-mn-ident-option-02] or [RFC2794] 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 agent address
      *  MN's home address
      *  IPsec SA between MN and HA, IKE pre-shared secret between MN
         and HA or shared secret/security association for authentication
         protocol [I-D.ietf-mip6-mn-auth-protocol-02]
   o  The bootstrapping procedure can be triggered at any time, either
      by the MN or by the network.  Bootstrapping can occur, for
      instance due to administrative action, information going stale, HA
      indicating the MN etc.  Bootstrapping may be initiated even when
      the MN is registered with the HA and has all the required
      credentials.  This may typically happen to refresh/renew the
      credentials.
   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 enable storage of
      user-specific information on entities other than the home agent.
   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 needs to 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 should 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.







































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5.  Motivation for bootstrapping

5.1  Addressing

   The default bootstrapping described in the Mobile IPv6 base
   specification [RFC3775] 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

   Currently, the home agent uses the mobile node's home address for
   authorization.  When manual keying is used, this happens through the
   security policy database, which specifies that a certain security
   association may only use a specific home address.  When dynamic
   keying is used, the home agent ensures that the IKE Phase 1 identity
   is authorized to request security associations for the given home
   address.  Mobile IPv6 uses IKEv1, which is unable to update the
   security policy database based on a dynamically assigned home
   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



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      the attachment to a particular visited network.


   Ease of deployment

      In order to simplify the deployment of Mobile IPv6, it is
      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 wherever 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 [RFC3775].  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 [RFC3775].

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 [RFC3775].

   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
   [RFC3776] 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 [RFC3775] 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, for example, be a commercial ASP, the IT
   department of an enterprise network, or the maintainer of a home
   (residential) network.

   If the mobile host is within the geographical area in which network
   access service is not provided by its home network access service
   provider, the mobile host is roaming.  The home network access
   service provider in this case acts as the access service authorizer,
   but the actual network access is provided by the serving network
   access provider.  During the authentication and authorization prior
   to the mobile host having Internet access, the serving network access
   provider may simply act as a routing agent for authentication and
   authorization back to the access service authorizer, or it may
   require an additional authentication and authorization step itself.
   An example of a roaming situation is when a business person is using
   a hotspot service in an airport, and the hotspot service provider has
   a roaming agreement with the business person's cellular provider.  In
   that case, the hotspot network is acting as the serving network
   access provider, while the cellular network is acting as the access
   service authorizer.  When the business person moves from the hotspot
   network to the cellular network, the cellular network is both the
   home access service provider and the access service authorizer.

   Mobility service using Mobile IPv6 is conceptually and possibly also
   in practice separate from network access service, though of course
   network access is required prior to providing mobility.  Mobile IPv6
   service enables an IPv6 host to maintain its reachability despite
   changing its network attachment point (subnets).  A network operator
   providing Mobile IPv6 service is called a mobility service provider
   (MSP).  Granting Mobile IPv6 service requires a host to authenticate
   and prove authorization for the service.  A network operator that
   authenticates a mobile host and authorizes mobility service is called
   a mobility service authorizer.  If both types of operation are
   performed by the same operator, that operator is called a home
   mobility service provider.  If authentication and authorization is



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   provided by one operator and the actual service is provider by
   another, the operator providing the service is called the serving
   mobility service provider.  The serving MSP must contact the mobile
   host's mobility service authorizer to check the mobile host's
   authorization prior to granting mobility service.

   The service model defined here clearly separates the entity providing
   the service from the entity that authentications and authorizes the
   service.  In the case of basic network access, this supports the
   traditional and well-known roaming model, in which inter-operator
   roaming agreements allow a host to obtain network access in areas
   where their home network access provider does not have coverage.  In
   the case of mobility service, this allows a roaming mobile host to
   obtain mobility service in the local operator's network while having
   that service authorized by the home operator.  The service model also
   allows mobility service and network access service to be provided by
   different entities.  This allows a network operator with no wireless
   access, like, for example, an enterprise network operator, to deploy
   a Mobile IPv6 home agent for mobility service while the actual
   wireless network access is provided by the serving network access
   providers with which the enterprise operator has a contract.  Here
   are some other possible combinations 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.  Also, the
   ASA and MSA 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 MSA's network.  Seed information needed to
   bootstrap the mobile node is considered in two cases:
   o  AAA authentication is mandatory for network access
   o  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 MSA 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
      (for example 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.
      If authentication protocol [I-D.ietf-mip6-mn-auth-protocol-02] is
      used, the shared key based security association with home agent is



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      needed.

   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

   There are two aspects of security for the Mobile IPv6 bootstrapping
   problem:
   1.  The security requirements imposed on the outcome of the
       bootstrapping process by RFC 3775 and other RFCs used by Mobile
       IPv6 for security.
   2.  The security of the bootstrapping process itself, in the sense of
       threats to the bootstrapping process imposed by active or passive
       attackers.

   Note that the two are related, in that if the bootstrapping process
   is compromised, the level of security required by RFC 3775 may not be
   obtained.

   The following two sections discuss these issues.

9.1  Security Requirements of Mobile IPv6

   The Mobile IPv6 specification in RFC 3775 requires the establishment
   of a collection of IPsec SAs between the home agent and mobile host
   to secure the signaling traffic for Mobile IP, and, optionally, also
   to secure data traffic.  The security of an IPsec SA required by the
   relevent IPsec RFCs must be quite strong.  Provisioning of keys and
   other cryptographic material during the establishment of the SA
   through bootstrapping must be done in a manner such that authenticity
   is proved and confidentiality is ensured.  In addition, the
   generation of any keying material or other cryptographic material for
   the SA must be done in a way such that the probability of compromise
   after the SA is in place is minimized.  The best way to minimize the
   probability of such a compromise is to have the cryptographic
   material only known or calculable by the two end nodes that share the
   SA, in this case, the home agent and mobile host.  If other parties
   are involved in the establishing the SA, through key distribution for
   example, the process should follow the constraints [eap_keying]
   designed to provide equivalent security.

   RFC 3775 also requires a trust relationship as defined in Section 1.3
   between the mobile host and mobility service provider.  This is
   necessary, for instance, to ensure that fradulent mobile hosts which
   attempt to flood other mobile hosts with traffic can not only be shut
   off but tracked down [I-D.rosec].  An infrastructureless relationship
   as defined in Section 1.3 does not satisfy this requirement.  Any
   bootstrapping solution must include a trust relationship between
   mobile host and mobility service provider.  Solutions that depend on
   an infrastructureless relationship are out of scope for
   bootstrapping.




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   Another requirement is that a home address is authorized to one
   specific host at a time.  RFC 3775 requires this in order to that
   misbehaving mobile hosts can be shut down.  This implies that, in
   addition to the IPsec SA, the home agent must somehow authorize the
   mobile host for a home address.  The authorization can be either
   implicit (for example, as a side effect of the authentication for
   mobility service) or explicit.  The authorization can either be done
   at the time the SA is created or dynamically managed through a first
   come, first served allocation policy.

9.2  Threats to the Bootstrapping Process

   Various attacks are possible on the bootstrapping process itself.
   These attacks can compromise the process such that the RFC 3775
   requirements for Mobile IP security are not met, or they can serve to
   simply disrupt the process such that bootstrapping cannot complete.
   Here are some possible attacks:
   o  An attacking network entity purporting to offer the mobile host a
      legitimate home agent address or boostrapping for the IPsec SAs
      may, instead, offer a bogus home agent address or configure bogus
      SAs that allow the home agent to steal the mobile host's traffic
      or otherwise disrupts the mobile host's mobility service.
   o  An attacking mobile host may attempt to steal mobility service by
      offering up fake credentials to a bootstrapping network entity or
      otherwise disrupt the home agent's ability to offer mobility
      service.
   o  A man in the middle on the link between the mobile host and the
      bootstrapping network entity could steal credentials or other
      sensitive information and use that to steal mobility service or
      deny it to the legitimate owner of the credentials.  Refer to
      Section 7.15 in [2284bis] and [I-D.mariblanca-aaa-eap-lla-00] for
      further information.
   o  An attacker could arrange for a distributed denial of service
      attack on the bootstrapping entity, to disrupt legitimate users
      from bootstrapping.

   In addition to these attacks, there are other considerations that are
   important in achieving a good security design.  As mobility and
   network access authentication are separate services, keys generated
   for these services need to be cryptographically separate, separately
   named, and have separate lifetimes, including if the keys are
   generated from the same authentication credentials  This is necessary
   because a mobile host must be able to move from one serving (or
   roaming) network access provider to another without needing to change
   its mobility access provider.  Finally, basic cryptographic processes
   must provide for multiple algorithms in order to accommodate the
   widely varying deployment needs.




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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 include Basavaraj
   Patil, Gerardo Giaretta, Jari Arkko, James Kempf, Yoshihiro Ohba,
   Ryuji Wakikawa, Hiroyuki Ohnishi, Mayumi Yanagiya Samita Chakrabarti,
   Gopal Dommety, Kent Leung, Alper Yegin, Hannes Tschofenig, Vijay
   Devarapalli, Kuntal Chowdury.

   The design team members can be reached at:

   Basavaraj Patil              basavaraj.patil@nokia.com

   Gerardo Giaretta             gerardo.giaretta@tilab.com

   Jari Arkko                   jari.arkko@kolumbus.fi

   James Kempf                  kempf@docomolabs-usa.com

   Yoshihiro Ohba               yohba@tari.toshiba.com

   Ryuji Wakikawa               ryuji@sfc.wide.ad.jp

   Hiroyuki Ohnishi             ohnishi.hiroyuki@lab.ntt.co.jp

   Mayumi Yanagiya              yanagiya.mayumi@lab.ntt.co.jp

   Samita Chakrabarti           Samita.Chakrabarti@eng.sun.com

   Gopal Dommety                gdommety@cisco.com

   Kent Leung                   kleung@cisco.com

   Alper Yegin                  alper.yegin@samsung.com

   Hannes Tschofenig            hannes.tschofenig@siemens.com

   Vijay Devarapalli            vijayd@iprg.nokia.com

   Kuntal Chowdury              kchowdury@starentnetworks.com











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11.  Acknowledgments

   Special thanks to James Kempf and Jari Arkko for writing the initial
   version of the bootstrapping statement.  Thanks to John Loughney for
   a detailed editorial review.














































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12.  References

12.1  Normative References

   [I-D.ietf-mip6-mn-auth-protocol-02]
              Patel et. al., A., "Authentication Protocol for Mobile
              IPv6", draft-ietf-mip6-auth-protocol-02.txt (work in
              progress), November 2004,

<http://www.ietf.org/internet-drafts/draft-ietf-mip6-auth-protocol-02.txt>
              .

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

<http://www.ietf.org/internet-drafts/draft-ietf-seamoby-mobility-terminology
-06.txt>
              .

   [RFC2794]  Calhoun, P. and C. Perkins, "Mobile IP Network Access
              Identifier Extension for IPv4", RFC 2794, March 2000.

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

   [RFC3776]  Arkko, J., Devarapalli, V. and F. Dupont, "Using IPsec to
              Protect Mobile IPv6 Signaling Between Mobile Nodes and
              Home Agents", RFC 3776, June 2004.

12.2  Informative References

   [2284bis]  Levkowetz, Ed., H., "Extensible Authentication Protocol
              (EAP)", February 2004,

<http://www.ietf.org/internet-drafts/draft-ietf-eap-rfc2284bis-09.txt>
              .

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

<http://www.ietf.org/internet-drafts/draft-giaretta-mip6-authorization-eap-0
0.txt>
              .

   [I-D.ietf-mip6-mn-ident-option-02]
              Patel, A., Leung, K., Akthar, H., Khalil, M. and K.
              Chowdhury, "Mobile Node Identifier Option for Mobile
              IPv6", draft-ietf-mip6-mn-ident-option-02.txt (work in
              progress), February 2004,

<http://www.ietf.org/internet-drafts/draft-ietf-mip6-mn-ident-option-02.txt>



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              .

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

<http://www.ietf.org/internet-drafts/draft-kempf-mip6-bootstrap-00.txt>
              .

   [I-D.mariblanca-aaa-eap-lla-00]
              Mariblanca, D., "EAP lower layer attributes for AAA
              protocols", May 2004,

<http://www.ietf.org/internet-drafts/draft-mariblanca-aaa-eap-lla-00.txt>
              .

   [I-D.rosec]
              Nikander, P., Arkko, J., Aura, T., Montenegro, G. and E.
              Nordmark, "Mobile IP version 6 Route Optimization Security
              Design Background", draft-ietf-mip6-ro-sec-02 (work in
              progress), October 2004,

<http://www.ietf.org/internet-drafts/draft-ietf-mip6-ro-sec-02.txt>
              .

   [eap_keying]
              Aboba et. al., B., "Extensible Authentication Protocol
              (EAP) Key Management Framework",
              draft-ietf-eap-keying-05.txt (work in progress), February
              2005,

<http://www.ietf.org/internet-drafts/draft-ietf-eap-keying-05.txt>
              .


Author's Address

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

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









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