Service Selection for Mobile IPv4
draft-korhonen-mip4-service-08

Network Working Group                                        J. Korhonen
Internet-Draft                                    Nokia Siemens Networks
Intended status: Informational                                U. Nilsson
Expires: July 13, 2009                                       TeliaSonera
                                                         January 9, 2009

                   Service Selection for Mobile IPv4
                   draft-korhonen-mip4-service-08.txt

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Abstract

   In some Mobile IPv4 deployments identifying the mobile node or the

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   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 to provide
   multiple services within a single mobility service subscription.
   This document describes a Service Selection Extension for Mobile IPv4
   that is intended to assist home agents to make specific service
   selections for the mobility service subscription during the
   registration procedure.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . . . 4
   3.  Service Selection Extension . . . . . . . . . . . . . . . . . . 4
   4.  Processing Considerations . . . . . . . . . . . . . . . . . . . 5
     4.1.  Mobile Node Considerations  . . . . . . . . . . . . . . . . 6
     4.2.  Home Agent Considerations . . . . . . . . . . . . . . . . . 6
     4.3.  Foreign Agent Considerations  . . . . . . . . . . . . . . . 7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 8
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 8
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 9

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1.  Introduction

   Mobile IPv4 [RFC3344] can identify mobile nodes in various ways,
   including home addresses [RFC3344] and Network Access Identifiers
   (NAI) [RFC4282][RFC2794].  In some Mobile IPv4 deployments
   identifying the mobile node or the mobility service subscriber via a
   Proxy Mobile IPv4 client [I-D.leung-mip4-proxy-mode] (hereafter the
   mobile node and the Proxy Mobile IPv4 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 assignment for mobility service providers
      based on the subscribed services.

   This document describes a Service Selection Extension for Mobile IPv4
   that is intended to assist home agents to make specific service
   selections for the mobility service subscription during the
   registration procedure.  Mobile IPv6 equivalent Service Selection
   Mobility Option has been described in [RFC5149].  The service
   selection may affect home agent routing decisions, Home Address
   assignment policies, firewall settings, and security policies.  When
   the service selection is used every Registration Request must contain
   the Service Selection extension.  The Service Selection extension
   from the Registration Request may be echoed back in the Registration
   Reply.

   In 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 would be allowed to all subscribers, but it is highly
   recommended in order to avoid having normal subscribers employ

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   operator-specific configuration values in order to get basic service.

   Some of the potential use-cases were listed earlier in this section.
   The general aim is better manageability of services and service
   provisioning from both operators and service providers point of view.
   However, it should be understood that there are potential deployment
   possibilities where selecting a certain service may restrict
   simultaneous access to other services from an user point of view
   (e.g., a "walled garden").  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 [RFC2119].

3.  Service Selection Extension

   At most one Service Selection extension MAY be included in any Mobile
   IPv4 Registration Request message.  When the service selection is
   used, the Service Selection extension MUST be included in every
   Registration Request message.  In absence of a specifically indicated
   service in the Registration Request for the initial registration or
   re-registration, the home agent MUST act as if the default service,
   such as plain Internet access had been requested.  The Service
   Selection extension MUST be placed in the Registration Request
   message as follows:

   o  When present the extension MUST appear after the MN-NAI extension,
      if the MN-NAI is also present in the message

   o  If the extension was added by the mobile node to a Registration
      Request it MUST appear prior to any authentication-enabling
      extensions [RFC3344][RFC4721]

   o  In the event the foreign agent adds the Service Selection
      extension to a Registration Request, the extension MUST appear
      prior to any Foreign-Home authentication-enabling extensions
      [RFC3344]

   The Home Agent MAY echo the received Service Selection extension
   option back in a Mobile IPv4 Registration Reply message.  The echoed
   Service Selection extension MUST be an unchanged copy of the Service
   Selection extension received in the corresponding Registration

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   Request message.  The Service Selection extension MUST be placed in
   the Registration Reply message as follows:

   o  If the extension was originally added by the mobile node to a
      Registration Request it MUST appear in the Registration Reply
      prior any authentication-enabling extensions [RFC3344][RFC4721]

   o  If the foreign agent added the Service Selection extension to a
      Registration Request, the extension MUST appear in the
      Registration Reply prior to any Foreign-Home authentication-
      enabling extensions [RFC3344]

   The Service Selection extension has the following format:

    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 = TBD1  |   Length      | Identifier...                 ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                        Service Selection Extension

   o  Type: 8-bit identifier set to TBD1 (to be defined by IANA) of the
      type of this skippable extension.

   o  Length: 8-bit unsigned integer, representing the length of the
      Service Selection Extension in octets, excluding the Type and
      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 [RFC3629], and formatted
      using Normalization Form KC (NFKC) as specified in [NFKC].

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

4.  Processing Considerations

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4.1.  Mobile Node Considerations

   A mobile node or its proxy representative MAY include the Service
   Selection extension into any Registration Request message.  The
   Service Selection extension can be used with any mobile node
   identification method.  The extension is used to identify the service
   to be associated with the mobility session and if the service
   selection is used, the Service Selection extension MUST be included
   into every Registration Request 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 its proxy representative is out of scope of this
   specification.

   If the mobile node receives a Registration Reply message with a Code
   set to SERVICE_AUTHORIZATION_FAILED and the mobile node has an
   existing binding with the Home Address used in the failed
   Registration Request message, the mobile node MUST delete the
   existing binding.  If there is no existing binding the mobile node
   proceeds as with any failed initial registration.

4.2.  Home Agent Considerations

   Upon receiving the Service Selection extension 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 to the service identified by the Service Selection
   extension.  The services the mobile node is authorized to SHOULD be
   part of the general mobile node subscription data.  If the mobile
   node is not authorized to the service, or the home agent does not
   recognize the identified service, the home agent MUST deny the
   registration and send a Registration Reply with a Code
   SERVICE_AUTHORIZATION_FAILED (error code TBD2).

   The Service Selection extension is used to assist the mobile node
   authorization phase and identifies a specific service that is to be
   authorized.  The Service Selection extension MAY also affect the Home
   Address allocation when for example used with the MN-NAI extension.
   For example, for the same NAI there MAY be different Home Addresses
   depending on the identified service.  Furthermore, the Service
   Selection extension 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 Registration Request message with a Service

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   Selection extension indicates a change in the selected service, then
   the home agent MUST re-authorize the mobile node.  The absence of the
   Service Selection extension MUST be treated as a request for the
   default service, which may also cause the re-authorization of the
   mobile node.  Depending on the home agent policies, the services
   policies, Home Address 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 Addresses.  If the
   authorization fails then the home agent MUST deny the registration,
   delete any binding with the existing Home Address and send a
   Registration Reply with a Code set to SERVICE_AUTHORIZATION_FAILED
   (error code TBD2).

   Depending on the local home agent policy, the home agent MAY echo
   back the Service Selection extension in the corresponding
   Registration Reply message towards the mobile node or the foreign
   agent.  The home agent MUST NOT change the content of the echoed
   Service Selection extension.

4.3.  Foreign Agent Considerations

   A foreign agent MUST skip the Service Selection extension if the
   Registration Request already contains the Service Selection
   extension.  If the Registration Request does not contain the Service
   Selection extension the foreign agent MAY add the Service Selection
   extension to the Registration Request message.  How the foreign agent
   learns the service the mobile nodes needs to authorize to is outside
   of scope of this document.

   In the case a foreign agent added the Service Selection extension to
   the Registration Request on behalf of the mobile node, it MUST verify
   whether the corresponding Registration Reply message from a home
   agent also contains an echoed Service Selection extension.  If the
   received Registration Reply message contains the echoed Service
   Selection extension, the foreign agent MUST NOT include the extension
   to the Registration Reply message that gets forwarded to the mobile
   node.

5.  Security Considerations

   The protection for the Service Selection extension depends on the
   service that is being identified and eventually selected.  If the
   service selection information should not be revealed on the wire it
   should be protected in a manner similar to Registration Requests and
   Registration Replies.  The Service Selection extension is protected
   by the same authentication enabling extension as the rest of the

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   Registration Request message.

   The home agent MUST verify that the mobile node is authorized to the
   service included in the Service Selection extension.  The Service
   Selection extension authorization is part of the normal mobile node
   registration and authentication procedure.  Both registration
   authentication and service authorization MUST succeed before the
   mobile node is allowed to register to the home agent.

6.  IANA Considerations

   A new Mobile IPv4 skippable Extension type is required for the
   following new Extension described in Section 3.  The Extension type
   must be from the 'skippable Extension' range (128-255):

       Service Selection Extension       is set to TBD1

   A new Mobile IPv4 registration denied by home agent error code is
   required.  The error code must be allocated from the 'Error Codes
   from the Home Agent' range (128-192):

       SERVICE_AUTHORIZATION_FAILED      is set to TBD2

7.  Acknowledgements

   The authors would like to thank Henrik Levkowetz, Kent Leung, Spencer
   Dawkins and Jari Arkko for their comments.  Jouni Korhonen also
   acknowledges TeliaSonera and TEKES MERCoNe project where most of the
   work was conducted.

8.  References

8.1.  Normative References

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

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3344]  Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
              August 2002.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

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8.2.  Informative References

   [I-D.leung-mip4-proxy-mode]
              Leung, K., "WiMAX Forum/3GPP2 Proxy Mobile IPv4",
              draft-leung-mip4-proxy-mode-10 (work in progress),
              December 2008.

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

   [RFC4282]  Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The
              Network Access Identifier", RFC 4282, December 2005.

   [RFC4721]  Perkins, C., Calhoun, P., and J. Bharatia, "Mobile IPv4
              Challenge/Response Extensions (Revised)", RFC 4721,
              January 2007.

   [RFC5149]  Korhonen, J., Nilsson, U., and V. Devarapalli, "Service
              Selection for Mobile IPv6", RFC 5149, February 2008.

Authors' Addresses

   Jouni Korhonen
   Nokia Siemens Networks
   Linnoitustie 6
   FIN-02600 Espoo
   FINLAND

   Email: jouni.nospam@gmail.com

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

   Email: ulf.s.nilsson@teliasonera.com

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