





Network Working Group                                        J. Laganier
Request for Comments: 5203                              DoCoMo Euro-Labs
Category: Experimental                                        T. Koponen
                                                                    HIIT
                                                               L. Eggert
                                                                   Nokia
                                                              April 2008


          Host Identity Protocol (HIP) Registration Extension

Status of This Memo

   This memo defines an Experimental Protocol for the Internet
   community.  It does not specify an Internet standard of any kind.
   Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

Abstract

   This document specifies a registration mechanism for the Host
   Identity Protocol (HIP) that allows hosts to register with services,
   such as HIP rendezvous servers or middleboxes.

1.  Introduction

   This document specifies an extension to the Host Identity Protocol
   (HIP) [RFC5201].  The extension provides a generic means for a host
   to register with a service.  The service may, for example, be a HIP
   rendezvous server [RFC5204] or a middlebox [RFC3234].

   This document makes no further assumptions about the exact type of
   service.  Likewise, this document does not specify any mechanisms to
   discover the presence of specific services or means to interact with
   them after registration.  Future documents may describe those
   operations.

   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 RFC 2119 [RFC2119].











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2.  Terminology

   In addition to the terminology defined in the HIP Architecture
   [RFC4423], the HIP specification [RFC5201], and the HIP Rendezvous
   Extension [RFC5204], this document defines and uses the following
   terms:

   Requester:
      a HIP node registering with a HIP registrar to request
      registration for a service.

   Registrar:
      a HIP node offering registration for one or more services.

   Service:
      a facility that provides requesters with new capabilities or
      functionalities operating at the HIP layer.  Examples include
      firewalls that support HIP traversal or HIP rendezvous servers.

   Registration:
      shared state stored by a requester and a registrar, allowing the
      requester to benefit from one or more HIP services offered by the
      registrar.  Each registration has an associated finite lifetime.
      Requesters can extend established registrations through re-
      registration (i.e., perform a refresh).

   Registration Type:
      an identifier for a given service in the registration protocol.
      For example, the rendezvous service is identified by a specific
      registration type.

3.  HIP Registration Extension Overview

   This document does not specify the means by which a requester
   discovers the availability of a service, or how a requester locates a
   registrar.  After a requester has discovered a registrar, it either
   initiates HIP base exchange or uses an existing HIP association with
   the registrar.  In both cases, registrars use additional parameters,
   which the remainder of this document defines, to announce their
   quality and grant or refuse registration.  Requesters use
   corresponding parameters to register with the service.  Both the
   registrar and the requester MAY also include in the messages
   exchanged additional HIP parameters specific to the registration type
   implicated.  Other documents will define parameters and how they
   shall be used.  The following sections describe the differences
   between this registration handshake and the standard HIP base
   exchange [RFC5201].




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3.1.  Registrar Announcing Its Ability

   A host that is capable and willing to act as a registrar SHOULD
   include a REG_INFO parameter in the R1 packets it sends during all
   base exchanges.  If it is currently unable to provide services due to
   transient conditions, it SHOULD include an empty REG_INFO, i.e., one
   with no services listed.  If services can be provided later, it
   SHOULD send UPDATE packets indicating the current set of services
   available in a new REG_INFO parameter to all hosts it is associated
   with.

3.2.  Requester Requesting Registration

   To request registration with a service, a requester constructs and
   includes a corresponding REG_REQUEST parameter in an I2 or UPDATE
   packet it sends to the registrar.

   If the requester has no HIP association established with the
   registrar, it SHOULD send the REG_REQUEST at the earliest
   possibility, i.e., in the I2 packet.  This minimizes the number of
   packets that need to be exchanged with the registrar.  A registrar
   MAY end a HIP association that does not carry a REG_REQUEST by
   including a NOTIFY with the type REG_REQUIRED in the R2.  In this
   case, no HIP association is created between the hosts.  The
   REG_REQUIRED notification error type is 51.

3.3.  Registrar Granting or Refusing Service(s) Registration

   Once registration has been requested, the registrar is able to
   authenticate the requester based on the host identity included in I2.
   It then verifies that the host identity is authorized to register
   with the requested service(s), based on local policies.  The details
   of this authorization procedure depend on the type of requested
   service(s) and on the local policies of the registrar, and are
   therefore not further specified in this document.

   After authorization, the registrar includes a REG_RESPONSE parameter
   in its response, which contains the service type(s) for which it has
   authorized registration, and zero or more REG_FAILED parameters
   containing the service type(s) for which it has not authorized
   registration or registration has failed for other reasons.  This
   response can be either an R2 or an UPDATE message, respectively,
   depending on whether the registration was requested during the base
   exchange, or using an existing association.  In particular,
   REG_FAILED with a failure type of zero indicates the service(s)
   type(s) that require further credentials for registration.





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   If the registrar requires further authorization and the requester has
   additional credentials available, the requester SHOULD try to
   register again with the service after the HIP association has been
   established.  The precise means of establishing and verifying
   credentials are beyond the scope of this document and are expected to
   be defined in other documents.

   Successful processing of a REG_RESPONSE parameter creates
   registration state at the requester.  In a similar manner, successful
   processing of a REG_REQUEST parameter creates registration state at
   the registrar and possibly at the service.  Both the requester and
   registrar can cancel a registration before it expires, if the
   services afforded by a registration are no longer needed by the
   requester, or cannot be provided any longer by the registrar (for
   instance, because its configuration has changed).

                 +-----+          I1          +-----+-----+
                 |     |--------------------->|     |  S1 |
                 |     |<---------------------|     |     |
                 |     |  R1(REG_INFO:S1,S2)  |     +-----+
                 | RQ  |                      |  R  |  S2 |
                 |     |    I2(REG_REQ:S1)    |     |     |
                 |     |--------------------->|     +-----+
                 |     |<---------------------|     |  S3 |
                 |     |    R2(REG_RESP:S1)   |     |     |
                 +-----+                      +-----+-----+

   A requester (RQ) registers with a registrar (R) of services (S1) and
            (S2), with which it has no current HIP association.



                 +-----+                      +-----+-----+
                 |     |  UPDATE(REG_INFO:S)  |     |     |
                 |     |<---------------------|     |     |
                 | RQ  |--------------------->|  R  |  S  |
                 |     |  UPDATE(REG_REQ:S)   |     |     |
                 |     |  UPDATE(REG_RESP:S)  |     |     |
                 |     |<---------------------|     |     |
                 +-----+                      +-----+-----+

   A requester (RQ) registers with a registrar (R) of services (S), with
           which it currently has a HIP association established.








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4.  Parameter Formats and Processing

   This section describes the format and processing of the new
   parameters introduced by the HIP registration extension.

4.1.  Encoding Registration Lifetimes with Exponents

   The HIP registration uses an exponential encoding of registration
   lifetimes.  This allows compact encoding of 255 different lifetime
   values ranging from 4 ms to 178 days into an 8-bit integer field.
   The lifetime exponent field used throughout this document MUST be
   interpreted as representing the lifetime value 2^((lifetime - 64)/8)
   seconds.

4.2.  REG_INFO

    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              |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Min Lifetime  | Max Lifetime  |  Reg Type #1  |  Reg Type #2  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      ...      |     ...       |  Reg Type #n  |               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    Padding    +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type           930
   Length         Length in octets, excluding Type, Length, and Padding.
   Min Lifetime   Minimum registration lifetime.
   Max Lifetime   Maximum registration lifetime.
   Reg Type       The registration types offered by the registrar.

   Other documents will define specific values for registration types.
   See Section 7 for more information.

   Registrars include the parameter in R1 packets in order to announce
   their registration capabilities.  The registrar SHOULD include the
   parameter in UPDATE packets when its service offering has changed.
   HIP_SIGNATURE_2 protects the parameter within the R1 packets.










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4.3.  REG_REQUEST

    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              |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Lifetime    |  Reg Type #1  |  Reg Type #2  |  Reg Type #3  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      ...      |     ...       |  Reg Type #n  |               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    Padding    +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type        932
   Length      Length in octets, excluding Type, Length, and Padding.
   Lifetime    Requested registration lifetime.
   Reg Type    The preferred registration types in order of preference.

   Other documents will define specific values for registration types.
   See Section 7 for more information.

   A requester includes the REG_REQUEST parameter in I2 or UPDATE
   packets to register with a registrar's service(s).  If the
   REG_REQUEST parameter is in an UPDATE packet, the registrar MUST NOT
   modify the registrations of registration types that are not listed in
   the parameter.  Moreover, the requester MUST NOT include the
   parameter unless the registrar's R1 packet or latest received UPDATE
   packet has contained a REG_INFO parameter with the requested
   registration types.

   The requester MUST NOT include more than one REG_REQUEST parameter in
   its I2 or UPDATE packets, while the registrar MUST be able to process
   one or more REG_REQUEST parameters in received I2 or UPDATE packets.

   When the registrar receives a registration with a lifetime that is
   either smaller or greater than the minimum or maximum lifetime,
   respectively, then it SHOULD grant the registration for the minimum
   or maximum lifetime, respectively.

   HIP_SIGNATURE protects the parameter within the I2 and UPDATE
   packets.









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4.4.  REG_RESPONSE

    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              |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Lifetime    |  Reg Type #1  |  Reg Type #2  |  Reg Type #3  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      ...      |     ...       |  Reg Type #n  |               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    Padding    +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type        934
   Length      Length in octets, excluding Type, Length, and Padding.
   Lifetime    Granted registration lifetime.
   Reg Type    The granted registration types in order of preference.

   Other documents will define specific values for registration types.
   See Section 7 for more information.

   The registrar SHOULD includes an REG_RESPONSE parameter in its R2 or
   UPDATE packet only if a registration has successfully completed.

   The registrar MUST NOT include more than one REG_RESPONSE parameter
   in its R2 or UPDATE packets, while the requester MUST be able to
   process one or more REG_RESPONSE parameters in received R2 or UPDATE
   packets.

   The requester MUST be prepared to receive any registration lifetime,
   including ones beyond the minimum and maximum lifetime indicated in
   the REG_INFO parameter.  It MUST NOT expect that the returned
   lifetime will be the requested one, even when the requested lifetime
   falls within the announced minimum and maximum.

   HIP_SIGNATURE protects the parameter within the R2 and UPDATE
   packets.













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4.5.  REG_FAILED

     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              |             Length            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Failure Type  |  Reg Type #1  |  Reg Type #2  |  Reg Type #3  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |      ...      |     ...       |  Reg Type #n  |               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    Padding    +
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    Type          936
    Length        Length in octets, excluding Type, Length, and Padding.
    Failure Type  Reason for failure.
    Reg Type      The registration types that failed with the specified
                  reason.

    Failure Type    Reason
    ------------    --------------------------------------------
    0               Registration requires additional credentials
    1               Registration type unavailable
    2-200           Unassigned
    201-255         Reserved by IANA for private use

   Other documents will define specific values for registration types.
   See Section 7 for more information.

   A failure type of zero means a registrar requires additional
   credentials to authorize a requester to register with the
   registration types listed in the parameter.  A failure type of one
   means that the requested service type is unavailable at the
   registrar.  Failure types other than zero (0) and one (1) have not
   been defined.

   The registrar SHOULD include the REG_FAILED parameter in its R2 or
   UPDATE packet, if registration with the registration types listed has
   not completed successfully and a requester is asked to try again with
   additional credentials.

   HIP_SIGNATURE protects the parameter within the R2 and UPDATE
   packets.







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5.  Establishing and Maintaining Registrations

   Establishing and/or maintaining a registration may require additional
   information not available in the transmitted REG_REQUEST or
   REG_RESPONSE parameters.  Therefore, registration type definitions
   MAY define dependencies for HIP parameters that are not defined in
   this document.  Their semantics are subject to the specific
   registration type specifications.

   The minimum lifetime both registrars and requesters MUST support is
   10 seconds, while they SHOULD support a maximum lifetime of 120
   seconds, at least.  These values define a baseline for the
   specification of services based on the registration system.  They
   were chosen to be neither too short nor too long, and to accommodate
   for existing timeouts of state established in middleboxes (e.g., NATs
   and firewalls.)

   A zero lifetime is reserved for canceling purposes.  Requesting a
   zero lifetime for a registration type is equal to canceling the
   registration of that type.  A requester MAY cancel a registration
   before it expires by sending a REG_REQ to the registrar with a zero
   lifetime.  A registrar SHOULD respond and grant a registration with a
   zero lifetime.  A registrar (and an attached service) MAY cancel a
   registration before it expires, at its own discretion.  However, if
   it does so, it SHOULD send a REG_RESPONSE with a zero lifetime to all
   registered requesters.

6.  Security Considerations

   This section discusses the threats on the HIP registration protocol,
   and their implications on the overall security of HIP.  In
   particular, it argues that the extensions described in this document
   do not introduce additional threats to HIP.

   The extensions described in this document rely on the HIP base
   exchange and do not modify its security characteristics, e.g.,
   digital signatures or HMAC.  Hence, the only threat introduced by
   these extensions is related to the creation of soft registration
   state at the registrar.

   Registrars act on a voluntary basis and are willing to accept being a
   responder and then to create HIP associations with a number of
   previously unknown hosts.  Because they have to store HIP association
   state anyway, adding a certain amount of time-limited HIP
   registration state should not introduce any serious additional
   threats, especially because HIP registrars may cancel registrations
   at any time at their own discretion, e.g., because of resource
   constraints during an attack.



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7.  IANA Considerations

   This section is to be interpreted according to the Guidelines for
   Writing an IANA Considerations Section in RFCs [RFC2434].

   This document updates the IANA Registry for HIP Parameter Types by
   assigning new HIP Parameter Types values for the new HIP Parameters
   defined in this document:

   o  REG_INFO (defined in Section 4.2)

   o  REG_REQUEST (defined in Section 4.3)

   o  REG_RESPONSE (defined in Section 4.4)

   o  REG_FAILED (defined in Section 4.5)

   IANA has allocated the Notify Message Type code 51 for the
   REG_REQUIRED notification error type in the Notify Message Type
   registry.

   IANA has opened a new registry for registration types.  This document
   does not define registration types but makes the following
   reservations:

   Reg Type        Service
   --------        -------
   0-200           Unassigned
   201-255         Reserved by IANA for private use

   Adding a new type requires new IETF specifications.

   IANA has opened a new registry for registration failure types.  This
   document makes the following failure type definitions and
   reservations:

   Failure Type    Reason
   ------------    --------------------------------------------
   0               Registration requires additional credentials
   1               Registration type unavailable
   2-200           Unassigned
   201-255         Reserved by IANA for private use

   Adding a new type requires new IETF specifications.







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8.  Acknowledgments

   The following people (in alphabetical order) have provided thoughtful
   and helpful discussions and/or suggestions that have helped to
   improve this document: Jeffrey Ahrenholz, Miriam Esteban, Mika Kousa,
   Pekka Nikander, and Hannes Tschofenig.

9.  References

9.1.  Normative References

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

   [RFC2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 2434,
              October 1998.

   [RFC5201]  Moskowitz, R., Nikander, P., Jokela, P., Ed., and T.
              Henderson, "Host Identity Protocol", RFC 5201, April 2008.

9.2.  Informative References

   [RFC3234]  Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and
              Issues", RFC 3234, February 2002.

   [RFC4423]  Moskowitz, R. and P. Nikander, "Host Identity Protocol
              (HIP) Architecture", RFC 4423, May 2006.

   [RFC5204]  Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
              Rendezvous Extension", RFC 5204, April 2008.




















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Authors' Addresses

   Julien Laganier
   DoCoMo Communications Laboratories Europe GmbH
   Landsberger Strasse 312
   Munich  80687
   Germany

   Phone: +49 89 56824 231
   EMail: julien.ietf@laposte.net
   URI:   http://www.docomolab-euro.com/


   Teemu Koponen
   Helsinki Institute for Information Technology
   Advanced Research Unit (ARU)
   P.O. Box 9800
   Helsinki  FIN-02015-HUT
   Finland

   Phone: +358 9 45 1
   EMail: teemu.koponen@iki.fi
   URI:   http://www.hiit.fi/


   Lars Eggert
   Nokia Research Center
   P.O. Box 407
   Nokia Group  00045
   Finland

   Phone: +358 50 48 24461
   EMail: lars.eggert@nokia.com
   URI:   http://research.nokia.com/people/lars_eggert/

















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Full Copyright Statement

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