Network Working Group C. Boulton Internet-Draft NS-Technologies Intended status: Standards Track August 16, 2010 Expires: February 17, 2011 A Session Description Protocol (SDP) Control Package Attribute draft-boulton-mmusic-sdp-control-package-attribute-05 Abstract This document defines a new Session Description Protocol (SDP) media- level attribute: "ctrl-package". The "ctrl-package" attribute conveys details of the SIP Control Framework extension packages that are supported by a client participating in an offer/answer exchange. 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 Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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Boulton Expires February 17, 2011 [Page 1] Internet-Draft Control Package Attribute August 2010 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions and Terminology . . . . . . . . . . . . . . . . . 4 3. The Ctrl-Package Attribute . . . . . . . . . . . . . . . . . . 5 4. The Ctrl-Package Attribute in the Offer/Answer Model . . . . . 7 5. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 9.1. Normative References . . . . . . . . . . . . . . . . . . . 12 9.2. Informative References . . . . . . . . . . . . . . . . . . 12 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13 Boulton Expires February 17, 2011 [Page 2] Internet-Draft Control Package Attribute August 2010 1. Introduction The MEDIACTRL work group of the IETF has defined a Media Control Channel Framework[I-D.boulton-sip-control-framework]. The Media Control Channel Framework introduces the concept of Control Packages which are extensions to the core connection framework. The Control Package extension documents allow for the base mechanism to be extended for specific usages, in a similar way that RFC 3265 [RFC3265] has 'Event Packages'. A good example is the Basic IVR Control Package[I-D.boulton-ivr-control-package] that is also defined by the MEDIACTRL work group for basic Interactive Voice Response. Control Packages are identified using a unique registered token in a similar mechanism to other IETF technologies such as RFC 3265 [RFC3265]. The core Media Control Channel Framework provides a dynamic, session level negotiation mechanism to decide on a common set of Control Packages that are supported by both clients participating in a control framework session. A mechanism does not exist for clients to identify SIP Control Packages supported before the control channel has been established. This specification defines the SDP 'ctrl-package' media-level attribute which provides an indication of Control Package extensions that are supported. Boulton Expires February 17, 2011 [Page 3] Internet-Draft Control Package Attribute August 2010 2. Conventions and Terminology In this document, BCP 14/RFC 2119 [RFC2119] defines the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL". In addition, BCP 15 indicates requirement levels for compliant implementations. Boulton Expires February 17, 2011 [Page 4] Internet-Draft Control Package Attribute August 2010 3. The Ctrl-Package Attribute This specification defines a new media-level value attribute: 'ctrl- package'. Its formatting in SDP is described by the following ABNF[RFC5234]. ctrl-package-attribute = "a=ctrl-package:" 1*(SP ctrl-package-name) CRLF ctrl-package-name = token token = 1*(token-char) token-char = %x21 / %x23-27 / %x2A-2B / %x2D-2E / %x30-39 / %x41-5A / %x5E-7E The token-char and token elements are defined in RFC 4566 [RFC4566] but included here to provide support for the implementer of this SDP feature. The values of a 'ctrl-package' attribute consists of a token that has been appropriately defined by the Media Control Channel Framework extension procedures for Control packages. This includes appropriate registration. The 'ctrl-package' attribute serves as a complimentary mechanism to the Control Package extension negotiation mechanism that is defined in the Media Control Channel Framework. It serves as an initial hint to the negotiating endpoints on exactly what Control Packages are supported when creating a new control channel. This can be beneficial both from a resource allocation perspective and it could also result in two clients identifying they are not capable of successful control channel interactions. This would lead to early abandonment of control channel setup (for example, a client may choose to terminate the associated SIP dialog and not attempt to make the connection). It should be noted that the 'ctrl-package' attribute does not have any context outside the creation of a control channel using the Media Control Channel Framework. It is simply to provide two Media Control Framework clients an opportunity to convey supported Control Packages. The Media Control Channel Framework has its own dynamic negotiation mechanism that is used to negotiate session level supported Control Packages. Allowing such additional semantics during an active Control Framework session would result in confusing and conflicting operation. For this reason, the 'ctrl-package' attribute MUST only be used in association with the value of 'new' defined for the 'connection' attribute in the COMEDIA[RFC4145] specification. This ensures that no conflicts take place between the Boulton Expires February 17, 2011 [Page 5] Internet-Draft Control Package Attribute August 2010 signalling layer and the underlying media control channel. Once a control channel has been established, the 'ctrl-package' attribute (and changes to it) has no impact on the Media Control Channel Framework session and should be ignored. Boulton Expires February 17, 2011 [Page 6] Internet-Draft Control Package Attribute August 2010 4. The Ctrl-Package Attribute in the Offer/Answer Model This specification does not define a means to discover whether or not the peer endpoint understands the 'ctrl-package' attribute because values contained in the attribute are informative and only intended as a hint at the offer/answer level. At the offer/answer level, the fact that an offer does not contain a 'ctrl-package' attribute does not imply that the answer should not contain one. As a result, this also implies that an offer containing a 'ctrl-package' attribute does not imply that the answer should contain one. Boulton Expires February 17, 2011 [Page 7] Internet-Draft Control Package Attribute August 2010 5. Example The following is an example of an SDP session description that uses the 'ctrl-package' attribute: v=0 o=originator 2890844526 2890842808 IN IP4 controller.example,com s=- i=A demo of the ctrl-package attribute c=IN IP4 controller.example.com t=0 0 m=application 7575 TCP/ESCS a=setup:active a=connection:new a=ctrl-package:msc-basic-ivr/1.0 Boulton Expires February 17, 2011 [Page 8] Internet-Draft Control Package Attribute August 2010 6. Security Considerations Security Considerations to be included in later versions of this document. Boulton Expires February 17, 2011 [Page 9] Internet-Draft Control Package Attribute August 2010 7. IANA Considerations Contact name: Chris Boulton cboulton@avaya.com. Attribute name: "ctrl-package". Type of attribute Media level. Subject to charset: Not. Purpose of attribute: The 'ctrl-package' attribute indicates supported Sip Control Framework extension documents that are supported in an associated media session. Allowed attribute values: A token. Boulton Expires February 17, 2011 [Page 10] Internet-Draft Control Package Attribute August 2010 8. Acknowledgments The authors would like to thank.... Boulton Expires February 17, 2011 [Page 11] Internet-Draft Control Package Attribute August 2010 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. [RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in the Session Description Protocol (SDP)", RFC 4145, September 2005. [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session Description Protocol", RFC 4566, July 2006. [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. 9.2. Informative References [I-D.boulton-ivr-control-package] Boulton, C., Melanchuk, T., and S. McGlashan, "A Basic Interactive Voice Response (IVR) Control Package for the Media Control Channel Framework", draft-boulton-ivr-control-package-06 (work in progress), February 2008. [I-D.boulton-sip-control-framework] Boulton, C., "A Control Framework for the Session Initiation Protocol (SIP)", draft-boulton-sip-control-framework-05 (work in progress), February 2007. [RFC3265] Roach, A., "Session Initiation Protocol (SIP)-Specific Event Notification", RFC 3265, June 2002. Boulton Expires February 17, 2011 [Page 12] Internet-Draft Control Package Attribute August 2010 Author's Address Chris Boulton NS-Technologies Email: chris@ns-technologies.com Boulton Expires February 17, 2011 [Page 13]