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Internet Engineering Task Force (IETF)                           K. JiaoRequest for Comments: 6737                                        HuaweiCategory: Standards Track                                        G. ZornISSN: 2070-1721                                              Network Zen                                                            October 2012The Diameter Capabilities Update ApplicationAbstract   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 is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6737.Copyright Notice   Copyright (c) 2012 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Jiao & Zorn                  Standards Track                    [Page 1]

RFC 6737              Diameter Capabilities Update          October 2012Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .22.  Specification of Requirements . . . . . . . . . . . . . . . . .23.  Diameter Protocol Considerations  . . . . . . . . . . . . . . .34.  Capabilities Update . . . . . . . . . . . . . . . . . . . . . .34.1.  Command Code Values . . . . . . . . . . . . . . . . . . . .44.1.1.  Capabilities-Update-Request . . . . . . . . . . . . . .44.1.2.  Capabilities-Update-Answer  . . . . . . . . . . . . . .55.  Security Considerations . . . . . . . . . . . . . . . . . . . .56.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .56.1.  Application Identifier  . . . . . . . . . . . . . . . . . .56.2.  Command Codes . . . . . . . . . . . . . . . . . . . . . . .57.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . . .58.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . .59.  References  . . . . . . . . . . . . . . . . . . . . . . . . . .69.1.  Normative References  . . . . . . . . . . . . . . . . . . .69.2.  Informative References  . . . . . . . . . . . . . . . . . .61.  Introduction   Capabilities exchange is an important component of the Diameter base   protocol [RFC6733], allowing peers to exchange identities and   Diameter capabilities (protocol version number, supported Diameter   applications, security mechanisms, etc.).  As defined inRFC 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 a 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.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 inRFC 2119 [RFC2119].Jiao & Zorn                  Standards Track                    [Page 2]

RFC 6737              Diameter Capabilities Update          October 20123.  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 10.  Diameter nodes   conforming to this specification MUST advertise support by including   the value 10 in the Auth-Application-Id of the Capabilities-Exchange-   Request (CER) and Capabilities-Exchange-Answer (CEA) commands   [RFC6733].4.  Capabilities Update   When the capabilities of a Diameter node conforming to this   specification change, the node MUST notify all of the nodes with   which it has an open transport connection and which 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 Attribute-Value   Pairs (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   Ids against all of the Application-Id 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 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 [RFC6733], and it 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[RFC6733], Section 2.4) MUST be interpreted as having common   applications with the peer.   As for CER/CEA messages, the CUR and CUA messages MUST NOT be   proxied, redirected, or relayed.Jiao & Zorn                  Standards Track                    [Page 3]

RFC 6737              Diameter Capabilities Update          October 2012   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 [RFC6733] 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).  The Diameter   Command Code Format (CCF) ([RFC6733], Section 3.2) is used in the   definitions.4.1.1.  Capabilities-Update-Request   The Capabilities-Update-Request (CUR), indicated by the Command Code   set to 328 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 the Stream Control Transmission Protocol   (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: 328, 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 ]Jiao & Zorn                  Standards Track                    [Page 4]

RFC 6737              Diameter Capabilities Update          October 20124.1.2.  Capabilities-Update-Answer   The Capabilities-Update-Answer, indicated by the Command Code set to   328 and the Command Flags' 'R' bit cleared, is sent in response to a   CUR message.                     Message Format                     <CUA> ::= < Diameter Header: 328 >                               { Origin-Host }                               { Origin-Realm }                               { Result-Code }                               [ Error-Message ]                             * [ AVP ]5.  Security Considerations   The security considerations applicable to the Diameter base protocol   [RFC6733] 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 10 (Diameter Capabilities   Update) from the Application Identifiers namespace [RFC6733].  SeeSection 3 for the assignment of the namespace in this specification.6.2.  Command Codes   This specification assigns the value 328 (Capabilities-Update-   Request/Capabilities-Update-Answer (CUR/CUA)) from the Command Codes   namespace [RFC6733].  SeeSection 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, Lionel   Morand, Dan Romascanu, Dan Harkins, and Ravi for helpful review and   discussion.Jiao & Zorn                  Standards Track                    [Page 5]

RFC 6737              Diameter Capabilities Update          October 20129.  References9.1.  Normative References   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC6733]  Fajardo, V., Arkko, J., Loughney, J., and G. Zorn,              "Diameter Base Protocol",RFC 6733, October 2012.9.2.  Informative References   [RFC4960]  Stewart, R., "Stream Control Transmission Protocol",RFC 4960, September 2007.Authors' Addresses   Jiao Kang   Huawei Technologies   Section F1, Huawei Industrial Base   Bantian, Longgang District   Shenzhen  518129   P.R. China   EMail: kangjiao@huawei.com   Glen Zorn   Network Zen   227/358 Thanon Sanphawut   Bang Na, Bangkok  10260   Thailand   Phone: +66 (0) 909-201060   EMail: glenzorn@gmail.comJiao & Zorn                  Standards Track                    [Page 6]