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INFORMATIONAL

Network Working Group                                        J. Korhonen
Request for Comments: 5149                                    U. Nilsson
Category: Informational                                      TeliaSonera
                                                          V. Devarapalli
                                                                  Azaire
                                                           February 2008


                   Service Selection for Mobile IPv6

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Abstract

   In some Mobile IPv6 deployments, identifying the mobile node or the
   mobility service subscriber is not enough to distinguish between
   multiple services possibly provisioned to the said mobile node and
   its mobility service subscription.  A capability to specify different
   services in addition to the mobile node identity can be leveraged to
   provide flexibility for mobility service providers on provisioning
   multiple services to one mobility service subscription.  This
   document describes a Service Selection Mobility Option for both
   conventional Mobile IPv6 and Proxy Mobile IPv6 that is intended to
   assist home agents to make a specific service selection for the
   mobility service subscription during the binding registration
   procedure.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Service Selection Mobility Option . . . . . . . . . . . . . . . 3
   4.  Processing Considerations . . . . . . . . . . . . . . . . . . . 4
     4.1.  Mobile Node Considerations  . . . . . . . . . . . . . . . . 4
     4.2.  Home Agent Considerations . . . . . . . . . . . . . . . . . 5
     4.3.  Correspondent Node Considerations . . . . . . . . . . . . . 5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 7





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1.  Introduction

   Mobile IPv6 [2] can identify mobile nodes in various ways, including
   home addresses [2], Network Access Identifiers (NAIs) [6][7], and
   credentials suitable for the Internet Key Exchange Protocol version 2
   (IKEv2) [10].  In some Mobile IPv6 deployments, identifying the
   mobile node or the mobility service subscriber via a Proxy Mobile
   IPv6 client [5] (hereafter, the mobile node and the Proxy Mobile IPv6
   client are used interchangeably) is not enough to distinguish between
   multiple services possibly provisioned to the said mobile node and
   its mobility service subscription.

   The capability to specify different services in addition to the
   mobile node identity can be leveraged to provide flexibility for
   mobility service providers to provide multiple services within the
   same mobility service subscription.  For example:

   o  Provide an enterprise data access for which the mobility service
      provider hosts connectivity and mobility services on behalf of the
      enterprise.

   o  Provide access to service domains that are otherwise not
      accessible from public networks because of some mobility service
      provider's business reasons.

   o  Provide simultaneous access to different service domains that are
      separated based on policies of the mobility service provider.

   o  Enable easier policy and quality of service assignment for
      mobility service providers based on the subscribed services.

   o  In the absence of a specifically indicated service, the home agent
      MUST act as if the default service, plain Internet access, had
      been requested.  There is no absolute requirement that this
      default service be allowed to all subscribers, but it is highly
      RECOMMENDED in order to avoid having normal subscribers employ
      operator-specific configuration values in order to get basic
      service.

   This document describes a Service Selection Mobility Option for
   Mobile IPv6 that is intended to assist home agents to make specific
   service selections for the mobility service subscription during the
   binding registration procedure.  The service selection may affect
   home agent routing decisions, Home Address or Home Network Prefix
   assignment policies, firewall settings, and security policies.  The
   Service Selection option should be used in every Binding Update that
   makes a new registration to the home agent.




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   Some of the potential use-cases were listed earlier in this section.
   The general aim is better manageability of services and service
   provisioning from the point of view of both operators and service
   providers.  However, it should be understood that there are potential
   deployment possibilities where selecting a certain service may
   restrict simultaneous access to other services from a user's point of
   view.  For example, services may be located in different
   administrative domains or external customer networks that practice
   excessive filtering of inbound and outbound traffic.

2.  Requirements

   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 [1].

3.  Service Selection Mobility Option

   At most one Service Selection Mobility Option MAY be included in any
   Binding Update message.  If the Binding Update message includes any
   authorization-related options (such as the Binding Authorization Data
   option [2]) or authentication related options (such as the Mobility
   Message Authentication option [8]), then the Service Selection option
   MUST appear before any mobility message authorization- or
   authentication-related options.

   The Service Selection option SHOULD NOT be sent to a correspondent
   node.  The mobile node cannot assume that the correspondent node has
   any knowledge about a specific service selection made between the
   mobile node and the home agent.

   The Service Selection option has no alignment requirement as such.


    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
                                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                   |  Type = 20    |   Length      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Identifier...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Service Selection Mobility Option








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   o  Type: 8-bit identifier set to 20 of the type of the skipable
      mobility option.

   o  Length: 8-bit unsigned integer, representing the length of the
      Service Selection Mobility Option in octets, excluding the Option
      Type and Option Length fields.  A value of zero (0) is not
      allowed.

   o  Identifier: A variable-length encoded service identifier string
      used to identify the requested service.  The identifier string
      length is between 1 and 255 octets.  This specification allows
      international identifier strings that are based on the use of
      Unicode characters, encoded as UTF-8 [3], and formatted using
      Normalization Form KC (NFKC) as specified in [4].

      'ims', 'voip', and 'voip.companyxyz.example.com' are valid
      examples of Service Selection option Identifiers.  At minimum, the
      Identifier MUST be unique among the home agents to which the
      mobile node is authorized to register.

4.  Processing Considerations

4.1.  Mobile Node Considerations

   A mobile node or a Proxy Mobile IPv6 client MAY include, at most, one
   Service Selection Mobility Option into a Binding Update message.  The
   option is used to identify the service to be associated with the
   binding registration and SHOULD only be included into the initial
   Binding Update message sent to a home agent.  If the mobile node
   wishes to change the selected service, it is RECOMMENDED that the
   mobile node de-register the existing binding with the home agent
   before proceeding with a binding registration for a different
   service.  The provisioning of the service identifiers to the mobile
   node or to the Proxy Mobile IPv6 client is out of the scope of this
   specification.

   The placement of the Service Selection option is as follows: when
   present, this option MUST appear after the Mobile Node-Network Access
   Identifier (MN-NAI) option, if the MN-NAI option is present, and
   before any authorization- and authentication-related options.  The
   Service Selection option can be used with any mobile node
   identification method such as a home address, an MN-NAI, and
   credentials suitable for IKEv2.

   If the mobile node receives a Binding Acknowledgement with a Status
   Code set to SERVICE_AUTHORIZATION_FAILED and the mobile node has an
   existing binding with the Home Address or the Home Network Prefix
   used in the failed Binding Update message, the mobile node MUST



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   delete the existing binding.  If there is no existing binding, the
   mobile node proceeds as with any failed initial binding registration.

4.2.  Home Agent Considerations

   Upon receiving a Binding Update message with a Service Selection
   option, the home agent authenticates and authorizes the mobile node.
   If the home agent supports the Service Selection, it MUST also verify
   that the mobile node is authorized for the service it included in the
   Service Selection option.  The services the mobile node is authorized
   for SHOULD be part of the general mobile node subscription profile.
   If the mobile node is not authorized for the service, the home agent
   MUST deny the registration and send a Binding Acknowledgement with a
   Status Code set to SERVICE_AUTHORIZATION_FAILED (151).

   The Service Selection option is used to assist the authorization and
   identifies a specific service that is to be authorized.  The Service
   Selection option MAY also affect the Home Address or the Home Network
   Prefix allocation when, for example, used with the MN-NAI option.
   For example, for the same NAI there MAY be different Home Addresses
   or Home Network Prefixes depending on the identified service.
   Furthermore, the Service Selection option MAY also affect the routing
   of the outbound IP packets in the home agent depending on the
   selected service.  The home agent MAY also apply different policy or
   quality of service treatment to traffic flows based on the selected
   service.

   If the newly arrived Binding Update message with a Service Selection
   option indicates a change in the selected service, then the home
   agent MUST re-authorize the mobile node.  Depending on the home agent
   policies, the services policies, Home Address or Home Network Prefix
   allocation policies, and the subscription policies, the home agent
   may or may not be able to authorize the mobile node to the new
   service.  For example, the existing service and the new service could
   require different Home Network Prefixes.  If the authorization fails,
   then the home agent MUST deny the registration, delete any binding
   with the existing Home Address or Home Network Prefix, and send a
   Binding Acknowledgement with a Status Code set to
   SERVICE_AUTHORIZATION_FAILED (151).

4.3.  Correspondent Node Considerations

   Unless the correspondent node and the home agent share the same
   knowledge about mobility services, the Service Selection option is
   more or less useless information to the correspondent node.  The
   correspondent node SHOULD silently ignore the Service Selection
   option in this case.




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   There are deployment cases where the home agent and a correspondent
   node, for example, belong to the same administrative domain.  In this
   case, it is possible that the correspondent node shares the same
   knowledge of the services as the home agent.  Therefore, the
   correspondent node is, for example, able to provide service-based
   traffic handling to mobile nodes.

5.  Security Considerations

   The protection for the Service Selection Mobility Option depends on
   the service that is being identified and eventually selected.  If the
   service selection information should not be revealed on the wire,
   Binding Updates and Binding Acknowledgements should use Encapsulating
   Security Payload (ESP) [9] in transport mode with a non-null
   encryption transform to provide message confidentiality.

6.  IANA Considerations

   A new Mobile IPv6 Mobility Option type has been assigned for the
   following new mobility option described in Section 3:

       Service Selection Mobility Option       is set to 20

   A new Mobile IPv6 registration denied by home agent Status Code has
   been assigned.  The Status Code was allocated from the range 128-255:

       SERVICE_AUTHORIZATION_FAILED            is set to 151

7.  Acknowledgements

   Jouni Korhonen would like to thank the TEKES MERCoNe project for
   providing funding to work on this document.  The authors would like
   to thank Jari Arkko for his thorough review.

8.  References

8.1.  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]   Yergeau, F., "UTF-8, a transformation format of ISO 10646",
         STD 63, RFC 3629, November 2003.





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   [4]   Davis, M. and M. Duerst, "Unicode Standard Annex #15; Unicode
         Normalization Forms", Unicode 5.0.0, October 2006.

8.2.  Informative References

   [5]   Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K., and
         B. Patil, "Proxy Mobile IPv6", Work in Progress, December 2007.

   [6]   Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The Network
         Access Identifier", RFC 4282, December 2005.

   [7]   Patel, A., Leung, K., Khalil, M., Akhtar, H., and K. Chowdhury,
         "Mobile Node Identifier Option for Mobile IPv6 (MIPv6)",
         RFC 4283, November 2005.

   [8]   Patel, A., Leung, K., Khalil, M., Akhtar, H., and K. Chowdhury,
         "Authentication Protocol for Mobile IPv6", RFC 4285,
         January 2006.

   [9]   Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303,
         December 2005.

   [10]  Devarapalli, V. and F. Dupont, "Mobile IPv6 Operation with
         IKEv2 and the Revised IPsec Architecture", RFC 4877,
         April 2007.


























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Authors' Addresses

   Jouni Korhonen
   TeliaSonera Corporation
   P.O. Box 970
   FIN-00051 Sonera
   Finland

   EMail: jouni.korhonen@teliasonera.com


   Ulf Nilsson
   TeliaSonera Corporation
   Marbackagatan 11
   S-123 86 Farsta
   Sweden

   EMail: ulf.s.nilsson@teliasonera.com


   Vijay Devarapalli
   Azaire Networks
   4800 Great America Pkwy
   Santa Clara, CA 95054
   USA

   EMail: vijay.devarapalli@azairenet.com
























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