Network Working Group                                            K. Jiao
Internet-Draft                                                    Huawei
Intended status: Standards Track                                 G. Zorn
Expires: November 25, December 20, 2010                                   Network Zen
                                                            May 24,
                                                           June 18, 2010

              The Diameter Capabilities Update Application
                 draft-ietf-dime-capablities-update-04
                 draft-ietf-dime-capablities-update-05

Abstract

   This document defines a new Diameter application and associated
   command codes.  The Capabilities Update application is intended to
   allow the dynamic update of certain Diameter peer capabilities while
   the peer-to-peer connection is in the open state.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on November 25, December 20, 2010.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Specification of Requirements . . . . . . . . . . . . . . . . . 3
   3.  Diameter Protocol Considerations  . . . . . . . . . . . . . . . 3
   4.  Capabilities Update . . . . . . . . . . . . . . . . . . . . . . 3
     4.1.  Command-Code Values . . . . . . . . . . . . . . . . . . . . 4
       4.1.1.  Capabilities-Update-Request . . . . . . . . . . . . . . 5
       4.1.2.  Capabilities-Update-Answer  . . . . . . . . . . . . . . 5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
     6.1.  Application Identifier  . . . . . . . . . . . . . . . . . . 6
     6.2.  Command Codes . . . . . . . . . . . . . . . . . . . . . . . 6
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . 6
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 6
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     9.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     9.2.  Informative References  . . . . . . . . . . . . . . . . . . 7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 7

1.  Introduction

   Capabilities exchange is an important component of the Diameter Base
   Protocol [RFC3588], [I-D.ietf-dime-rfc3588bis], allowing peers to exchange
   identities and Diameter capabilities (protocol version number,
   supported Diameter applications, security mechanisms, etc.).  As
   defined in RFC 3588, however, the capabilities exchange process takes
   place only once, at the inception of a transport connection between a
   given pair of peers.  Therefore, if a peer's capabilities change (due
   to software update, for example), the existing connection(s) must be
   torn down (along with all of the associated user sessions) and
   restarted before the modified capabilities can be advertised.

   This document defines a new Diameter application intended to allow
   the dynamic update of a subset of Diameter peer capabilities over an
   existing connection.  Because the Capabilities Update application
   specified herein operates over an existing transport connection,
   modification of certain capabilities is prohibited.  Specifically,
   modifying the security mechanism in use is not allowed; if the
   security method used between a pair of peers is changed the affected
   connection MUST be restarted.

   Discussion of this draft may be directed to the dime Working Group of
   the IETF (dime@ietf.org).

2.  Specification of 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 RFC 2119 [RFC2119].

3.  Diameter Protocol Considerations

   This section details the relationship of the Diameter Capabilities
   Update application to the Diameter Base Protocol.

   This document specifies Diameter Application-ID <TBD1>.  Diameter
   nodes conforming to this specification MUST advertise support by
   including the value <TBD1> in the Auth-Application-Id of the
   Capabilities-Exchange-Req
   Capabilities-Exchange-Request and Capabilities-Exchange-Answer
   commands
   [RFC3588]. [I-D.ietf-dime-rfc3588bis].

4.  Capabilities Update

   When the capabilities of a Diameter node conforming to this
   specification change, it SHOULD MUST notify all of the nodes with which it
   has an open transport connection and have also advertised support for
   the Capabilities Update application using the Capabilities-Update-
   Request (CUR) message (Section 4.1.1).  This message allows the
   update of a peer's capabilities (supported Diameter applications,
   etc.).

   A Diameter node only issues a given command to those peers that have
   advertised support for the Diameter application that defines the
   command.  A Diameter node MUST cache the supported applications in
   order to ensure that unrecognized commands and/or AVPs are not
   unnecessarily sent to a peer.

   The receiver of the CUR MUST determine common applications by
   computing the intersection of its own set of supported Application Id
   against all of the application identifier AVPs (Auth-Application-Id,
   Acct-Application-Id and Vendor-Specific- Application-Id) present in
   the CUR.  The value of the Vendor-Id AVP in the Vendor-Specific-
   Application-Id MUST NOT be used during computation.

   If the receiver of a Capabilities-Update-Req (CUR) message CUR does not have any applications in common
   with the sender then it MUST return a Capabilities-Update-Answer
   (CUA) (Section 4.1.2) with the Result-Code AVP set to
   DIAMETER_NO_COMMON_APPLICATION, and SHOULD disconnect the transport
   layer connection; however, if active sessions are using the
   connection, peers MAY delay disconnection until the sessions can be
   redirected or gracefully terminated.  Note that receiving a CUA from
   a peer advertising itself as a Relay (see [RFC3588], [I-D.ietf-dime-rfc3588bis],
   Section 2.4) MUST be interpreted as having common applications with
   the peer.

   The CUR and CUA messages MUST NOT be proxied, redirected or relayed.

   Even though the CUR/CUA messages cannot be proxied, it is still
   possible for an upstream agent to receive a message for which there
   are no peers available to handle the application that corresponds to
   the Command-Code.  This could happen if, for example, the peers are
   too busy or down.  In such instances, the 'E' bit MUST be set in the
   answer message with the Result-Code AVP set to
   DIAMETER_UNABLE_TO_DELIVER to inform the downstream peer to take
   action (e.g., re-routing requests to an alternate peer).

4.1.  Command-Code Values

   This section defines Command-Code [RFC3588] [I-D.ietf-dime-rfc3588bis] values
   that MUST be supported by all Diameter implementations conforming to
   this specification.  The following Command Codes are defined in this
   document: Capabilities-Update-Request (CUR, Section 4.1.1) and
   Capabilities-Update-Answer (CUA, Section 4.1.2).

4.1.1.  Capabilities-Update-Request

   The Capabilities-Update-Request (CUR), indicated by the Command-Code
   set to <TBD2> and the Command Flags' 'R' bit set, is sent to update
   local capabilities.  Upon detection of a transport failure, this
   message MUST NOT be sent to an alternate peer.

   When Diameter is run over SCTP [RFC4960], which allows connections to
   span multiple interfaces and multiple IP addresses, the Capabilities-
   Update-Request message MUST contain one Host-IP-Address AVP for each
   potential IP address that may be locally used when transmitting
   Diameter messages.

   Message Format

      <CUR> ::= < Diameter Header: TBD2, REQ >
                { Origin-Host }
                { Origin-Realm }
             1* { Host-IP-Address }
                { Vendor-Id }
                { Product-Name }
                [ Origin-State-Id ]
              * [ Supported-Vendor-Id ]
              * [ Auth-Application-Id ]
              * [ Acct-Application-Id ]
              * [ Vendor-Specific-Application-Id ]
                [ Firmware-Revision ]
              * [ AVP ]

4.1.2.  Capabilities-Update-Answer

   The Capabilities-Update-Answer Capabilities-Update-Answer, indicated by the Command-Code set to
   <TBD3> and the Command Flags' 'R' bit set, cleared, is sent in response to
   a CUR message.

                    Message Format

                    <CUA> ::= < Diameter Header: TBD3 >
                              { Origin-Host }
                              { Origin-Realm }
                              { Result-Code }
                              [ Error-Message ]
                            * [ AVP ]

5.  Security Considerations

   The security considerations applicable to the Diameter Base Protocol
   [RFC3588]
   [I-D.ietf-dime-rfc3588bis] are also applicable to this document.

6.  IANA Considerations

   This section explains the criteria to be used by the IANA for
   assignment of numbers within namespaces used within this document.

6.1.  Application Identifier

   This specification assigns the value <TBD1> from the Application
   Identifiers namespace defined in RFC 3588.  See Section 3 for the
   assignment of the namespace in this specification.

6.2.  Command Codes

   This specification assigns the values <TBD2> and <TBD3> from the
   Command Codes namespace defined in RFC 3588.  See Section 4.1 for the
   assignment of the namespace in this specification.

7.  Contributors

   This document is based upon work done by Tina Tsou.

8.  Acknowledgements

   Thanks to Sebastien Decugis, Niklas Neumann, Subash Comerica Comerica, Lionel
   Morand and Ravi for helpful discussion.

9.  References

9.1.  Normative References

   [I-D.ietf-dime-rfc3588bis]
              Fajardo, V., Arkko, J., Loughney, J., and G. Zorn,
              "Diameter Base Protocol", draft-ietf-dime-rfc3588bis-21
              (work in progress), June 2010.

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

   [RFC3588]  Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
              Arkko, "Diameter Base Protocol", RFC 3588, September 2003.

9.2.  Informative References

   [RFC4960]  Stewart, R., "Stream Control Transmission Protocol",
              RFC 4960, September 2007.

Authors' Addresses

   Jiao Kang
   Huawei Technologies
   Section B1, Huawei Industrial Base
   Bantian, Longgang District
   Shenzhen  518129
   P.R. China

   Phone: +86 755 2878-6690
   Email: kangjiao@huawei.com

   Glen Zorn
   Network Zen
   1463 East Republican Street
   #358
   Seattle, WA  98112
   USA

   Email: gwz@net-zen.net