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Network Working Group                                         G. Wolfner
Internet-Draft                                          J. Korhonen, Ed.
Intended status: Informational                    Nokia Siemens Networks
Expires: April 7, 2010                                   October 4, 2009


              Connection Identifier for Proxy Mobile IPv6
                draft-wolfner-netext-pmip6-connid-01.txt

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
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Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
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Abstract

   This document describes a Connection Identifier mobility option for
   Proxy Mobile IPv6.  The new mobility option can be used to uniquely
   identify multiple mobility sessions to the same selected service, for



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   example, in the Evolved Packet System scope.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . . . 4
   3.  Proxy Mobile IPv6 Domain Assumptions  . . . . . . . . . . . . . 4
   4.  Connection Identifier Mobility Option . . . . . . . . . . . . . 4
   5.  Extensions to Conceptual Data Structures and Lookups  . . . . . 5
     5.1.  Binding Cache . . . . . . . . . . . . . . . . . . . . . . . 5
     5.2.  Binding Update List . . . . . . . . . . . . . . . . . . . . 5
     5.3.  Lookup Keys . . . . . . . . . . . . . . . . . . . . . . . . 5
   6.  Processing Considerations . . . . . . . . . . . . . . . . . . . 6
     6.1.  Capability Exchange . . . . . . . . . . . . . . . . . . . . 6
     6.2.  Mobile Access Gateway Considerations  . . . . . . . . . . . 6
     6.3.  Local Mobility Anchor Considerations  . . . . . . . . . . . 6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 7
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     10.1. Normative References  . . . . . . . . . . . . . . . . . . . 7
     10.2. Informative References  . . . . . . . . . . . . . . . . . . 8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 8



























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1.  Introduction

   A Mobile Node (MN) may have several mobility sessions via a single
   interface with the same Local Mobility Anchor (LMA).  An example
   where a MN may have several mobility sessions with the same LMA is
   the 3GPP environment using Enhanced Packet Core (EPC) [3GPP.23.401]
   [3GPP.23.402].  In the 3GPP environment these mobility sessions are
   called PDN connections (PDN stands for the Packet Data Network), and
   PDN connections to the same service defined by an Access Point Name
   (APN) use the same LMA instance.  In 3GPP access networks these PDN
   connections of a single MN can be identified by a unique identifier
   called EPS bearer identifier (EPS stands for the Evolved Packet
   System).  Moreover, 3GPP EPC system can be used with access networks
   that are not defined by the 3GPP such as CDMA or WLANs.  These access
   networks are generally referred as non-3GPP accesses.  Therefore, an
   unique identification of mobility sessions of a MN with the same LMA
   is also needed with those non-3GPP access networks.

   It has been identified that base Proxy Mobile IPv6 (PMIPv6) [RFC5213]
   parameters and existing IETF standardized mobility options are not
   enough in the EPC scope.  Generally in PMIPv6 and especially in the
   EPC, different APNs are identified using the Service Selection
   mobility option [RFC5149].  However, in a case of multiple PDN
   connections to the same APN, and assuming that Home Network Prefixes
   (HNP) are not always available in a Mobile Access Gateway (MAG) after
   a handover and that the "APN name" in the Service Selection mobility
   option cannot be decorated (i.e. making each APN unique), there is a
   need for a new identifier to uniquely identify PDN connections to the
   same APN.  Note that an optional GRE key option defined in
   [I-D.ietf-netlmm-grekey-option] as such does not help to
   differentiate the mobility sessions.  The reason for this is that
   only the downlink GRE key is included in the Proxy Binding Update
   (PBU) messages, and the downlink GRE key option is local to MAG.
   Therefore, the preservation of the same downlink GRE key values
   during inter-MAG handovers cannot be guaranteed.

   This document describes a new Connection Identifier (CID) mobility
   option for PMIPv6.  The Connection Identifier mobility option enables
   that a MN can have several mobility sessions via a single interface
   with the same LMA by carrying an unique connection identifier.  This
   allows the MAG and the LMA to uniquely identify mobility sessions of
   a MN.  The combination of MN-Identifier + Service Selection +
   Connection Identifier can uniquely identify mobility sessions even if
   the selected service on each mobility session for the same MN-
   Identifier are the same.  Furthermore, if Service Selection [RFC5149]
   is not used or supported, the Connection Identifier functionality can
   still be used to manage multiple HNPs individually on a single
   interface.  Effectively that means a combination of MN-Identifier +



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   Connection Identifier can uniquely identify mobility sessions of a
   MN.  This allows a MN to configure additional HNPs to an interface
   that is already assigned with a HNP.

   How the Connection Identifier is created and learnt by the MAG, is
   out of the scope of this document.  The identifier is required to be
   available in a MAG already when a PBU is to be sent and guaranteed to
   preserve its value when a MN handoffs from a MAG to another.  The MAG
   may learn this identifier for example from "lower layers" or external
   control signaling during the PDN connection setup.  The identifier
   could even be an uplink GRE key if that is readily available in a MAG
   when a PBU gets sent.  After a successful creation of a mobility
   session, and an allocation of the Connection Identifier, both the MAG
   and LMA MUST include the Connection Identifier in all subsequent
   PMIPv6 signaling messages related to that mobility session.


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.  Proxy Mobile IPv6 Domain Assumptions

   The functionality described in this specification is supported only
   when multiple mobility sessions to the same selected service are
   anchored to a single LMA.  Also the multiple mobility sessions to the
   same selected service that the MN is using go via the same MAG.


4.  Connection Identifier Mobility Option

   At most one Connection Identifier mobility option MAY be included in
   any PBU message sent by the MAG.  The LMA MUST echo the received
   Connection Identifier back in a Proxy Binding Acknowledgement (PBA)
   message, assuming the LMA understands the Connection Identifier
   mobility option in the first place.  The echoed Connection Identifier
   mobility option MUST be an unchanged copy of the Connection
   Identifier mobility option received in the corresponding PBU message.

   The Connection Identifier mobility option has the alignment
   requirement of 4n+2 and the following format:







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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
                                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                   | Option Type   | Option Length |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Connection Identifier                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Connection Identifier Mobility Option

   Option Type

      8-bit identifier set to TBD1.

   Option Length

      8-bit unsigned integer, representing the length in octets of the
      mobility option, not including the Option Type and Option Length
      fields.

   Connection Identifier

      A 32-bit identifier value.  The value is in network order.



5.  Extensions to Conceptual Data Structures and Lookups

5.1.  Binding Cache

   Each Binding Cache Entry (BCE) MUST be extended with a Connection
   Identifier parameter.  This concerns only LMAs that implement the
   Connection Identifier mobility option and the associated
   functionality.

5.2.  Binding Update List

   Each Binding Update List Entry (BULE) MUST be extended with a
   Connection Identifier parameter.  This concerns only MAGs that
   implement the Connection Identifier mobility option and the
   associated functionality.

5.3.  Lookup Keys

   Both BCE and BULE MAY be queried using the Connection Identifier
   mobility option value as one additional lookup key.  The lookup key
   combination:




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      MN-Identifier + Service Selection + Connection Identifier

   MUST uniquely identify a single BCE or a BULE.

   In a case Service Selection [RFC5149] is not used at all or supported
   by a MAG-LMA pair, then the lookup key combination:

      MN-Identifier + Connection Identifier

   MUST uniquely identify a single BCE or a BULE.


6.  Processing Considerations

6.1.  Capability Exchange

   The Connection Identifier mobility option in the PBU is also an
   indication to a LMA that the MAG supports multiple mobility sessions
   to the same selected service (identified by the Service Selection
   mobility option).  Similarly, the Connection Identifier mobility
   option in the PBA is an indication to the MAG that the LMA supports
   the multiple mobility sessions to the same selected service.  Using
   this simple mechanism the MAG and the LMA can dynamically find out
   whether both support the multiple mobility sessions to the same
   selected service functionality.

6.2.  Mobile Access Gateway Considerations

   If the multiple mobility session to the same selected service
   functionality is enabled and mutually supported by the MAG and the
   LMA, then the MAG MUST include the Connection Identifier mobility
   option in all PBUs.  How the MAG maps connections originated from the
   MN to connection identifiers is out of scope of this specification.
   The mapping of mobility sessions and connection identifiers MUST
   remain the lifetime of the mobility session.

   How the MAG knows/learns the connection identifiers after a handover
   between MAGs is out of scope of this specification.  However,
   mechanisms such as context transfer between MAGs may be used.

6.3.  Local Mobility Anchor Considerations

   If the multiple mobility session to the same selected service
   functionality is enabled and mutually supported by the MAG and the
   LMA, then the LMA MUST echo the Connection Identifier mobility option
   in all PBAs that it received in the corresponding PBUs.

   In a case the LMA does not support the Connection Identifier mobility



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   option, the LMA MUST silently ignore the option and process the
   remaining of the PBU as defined in [RFC5213] and [RFC5149].  It is
   implementation specific which BCE for a given MN-Identifier is
   returned when e.g. the BC lookup using the MN-Identifier and the
   Service Selection option as the lookup key match multiple BCEs.


7.  Security Considerations

   The protection for the Connection Identifier mobility option depends
   on the services that are being connected to.  If the Connection
   Identifier information should not be revealed on the wire, Proxy
   Binding Updates and Proxy Binding Acknowledgements should use
   Encapsulating Security Payload (ESP) [RFC4303] in transport mode with
   a non-null encryption transform to provide message confidentiality.


8.  IANA Considerations

   A new mobility option for the use with PMIPv6 is defined in the
   [RFC3775] "Mobility Options" registry.  The mobility options are
   defined in Section 4:

     Connection Identifier mobility option   is set to TBD1


9.  Acknowledgements

   The authors thank Basavaraj Patil and Xiangsong Cui for their
   comments and discussion on this document.


10.  References

10.1.  Normative References

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

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

   [RFC5213]  Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
              and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.







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10.2.  Informative References

   [3GPP.23.401]
              3GPP, "General Packet Radio Service (GPRS) enhancements
              for Evolved Universal Terrestrial Radio Access Network
              (E-UTRAN) access", 3GPP TS 23.401 8.6.0, June 2009.

   [3GPP.23.402]
              3GPP, "Architecture enhancements for non-3GPP accesses",
              3GPP TS 23.402 8.6.0, June 2009.

   [I-D.ietf-netlmm-grekey-option]
              Muhanna, A., Khalil, M., Gundavelli, S., and K. Leung,
              "GRE Key Option for Proxy Mobile IPv6",
              draft-ietf-netlmm-grekey-option-09 (work in progress),
              May 2009.

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, December 2005.

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


Authors' Addresses

   Gyorgy Wolfner
   Nokia Siemens Networks

   Email: gyorgy.wolfner@nsn.com


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

   Email: jouni.nospam@gmail.com












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