Sipcore Working Group A. Allen, Ed. Internet-Draft Blackberry Intended status: Informational July 3, 2014 Expires: January 4, 2015 Internet Assigned Numbers Authority (IANA) Registration of the Session Initiation Protocol (SIP) Feature-Capability indicators draft-allen-sipcore-sip-tree-cap-indicators-01 Abstract This document registers with IANA the SIP Feature-Capability indicators in the "SIP Feature-Capability Indicator Registration Tree" of the IANA "Proxy-Feature Feature-Capability Indicator Trees" registry for use with the SIP Feature-Caps header field. 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/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on January 4, 2015. Copyright Notice Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 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. Allen Expires January 4, 2015 [Page 1] Internet-Draft SIP Capability Indicators July 2014 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. SIP Feature-Capability indicators . . . . . . . . . . . . . . 4 4. Security Considerations . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 5.1. Audio . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.2. Application . . . . . . . . . . . . . . . . . . . . . . . 6 5.3. Data . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5.4. Control . . . . . . . . . . . . . . . . . . . . . . . . . 7 5.5. Video . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.6. Text . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.7. Duplex . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.8. Description . . . . . . . . . . . . . . . . . . . . . . . 11 5.9. Event Packages . . . . . . . . . . . . . . . . . . . . . . 11 5.10. Priority . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.11. Methods . . . . . . . . . . . . . . . . . . . . . . . . . 13 5.12. Extensions . . . . . . . . . . . . . . . . . . . . . . . . 14 5.13. Schemes . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.14. Is Focus . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.15. Message . . . . . . . . . . . . . . . . . . . . . . . . . 16 5.16. Interactive Connectivity Establishment . . . . . . . . . . 17 5.17. Application Subtype . . . . . . . . . . . . . . . . . . . 17 5.18. Fax . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19 7.1. Normative References . . . . . . . . . . . . . . . . . . . 19 7.2. Informative References . . . . . . . . . . . . . . . . . . 20 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 21 Allen Expires January 4, 2015 [Page 2] Internet-Draft SIP Capability Indicators July 2014 1. Introduction RFC 6809 [1] specifies the SIP Feature-Caps header field thst conveys feature-capability indicators that are used to indicate support of features and capabilities for SIP entities that are not represented by the Uniform Resource Identifier (URI) of the Contact header field. RFC 6809 [1] also creates a new IANA registry, "Proxy-Feature Feature-Capability Indicator Trees", for registering feature- capability indicators including a SIP feature-capability indicator tree for registering SIP feature-capability indicators that is similar to the media feature tag SIP tree defined in RFC 3840 [2]. This document populates this SIP tree with some feature-capability indicators that are based upon those already defined in RFC 3840 [2], RFC 4569 [3], RFC 5768 [4], RFC 5688 [5] and RFC 6913 [6]. 2. Motivation SIP sessions often involve intermediaries (typically acting as B2BUAs) that in addition to forwarding SIP requests and responses can also act as UAs to perform more complex manipulations of the session. Examples of such intermediaries include IP PBXs (Internet Protocol Private Brance Exchanges), Telephony Call Feature Application Servers and Session Transfer Anchor Points. Often the manipulations of the session by the intermediary are initiated by one of the UAs in the session sending a request (such as REFER request) to the intermediary to for example transfer the session or create a conference. Additionally UAs may also need to subscribe to events related to the session with the intermediary accepting such subscritions and providing the notification of event state changes. Typically such functionality has been achieved by sending such REFER and SUBSCRIBE requests within the established dialog for the session, with the intermediary then intercepting and processing the REFER or SUBSCRIBE request rather than forwarding it to the remote UAS. However such dialog reuse has been problematic and RFC 6665 [7] has deprecated dialog reuse (except for legacy interoperability). However, in order to avoid reusing the same dialog as the session and achieve equivalent functionality when interacting with intermediaries using for instance REFER request requires that the UA obtain the Globally Routable User Agent URI (GRUU) of the intermediary and also know that the intermediary supports the relevant capabilities such as the required SIP methods (i.e. REFER) as well as the needed SIP extensions, (such as target dialog extension specified in RFC 4538 in [8]). Typically B2BUAs have acted as two UAs back-to-back with the Contact URI being the URI of the B2BUA. However this means that GRUU of the Allen Expires January 4, 2015 [Page 3] Internet-Draft SIP Capability Indicators July 2014 UA is overwritten by the B2BUA and the meaning of the Contact header field parameters becomes obscure. Do the Contact header field parameters reflect the capabilities of the Contact address (i.e the B2BUA) or do they reflect the capabilities of the remote UA? If they relect the capabilities of the B2BUA then the identfication of the capabilities of the remote UA have been lost. If they reflect the capabilities of the remote UA then they falsely identify that the B2BUA contact address has the capabilities of the remote UA. Another use case for B2BUAs is in control of Application Level Gateways (ALGs). These ALGs are controlled by SIP intermediaries that act as routing B2BUs and perform media functions such as IP address translation, transcoding, and media policing. Such ALGs may only support some media types while blocking others. It is useful if the media types that are allowed can be communciated to other entities in the SIP signaling so that fruitless attempts to establish sessions with media types that will not be allowed are not attempted. What is needed is a way for intermediaries to pass the remote UA's contact address and capabilities transparently in the Contact header field while being able to indicate their own contact address (i.e GRUU) and associated capabilities to the UA. RFC 6809 [1] provides that addresses of intermediaries can be communicated as a value of an associated feature-capability indicator so it would be appropriate to define feature capability indicators as part of the global tree to communicate the GRUU of the intermediary and hence this is outside the scope of this document. The feature- capability indicators for communicating SIP related capabilities (e.g supported SIP Methods and extensions) though need to be registered in the SIP tree. 3. SIP Feature-Capability indicators The following media feature tags from RFC 3840 [2]", RFC 4569 [3], RFC 5768 [4], RFC 5688 [5] and RFC 6913 [6] are considered to be useful to also be defined as Feature-Capability indicators: sip.audio sip.application sip.data sip.control sip.video sip.text sip.duplex sip.description Allen Expires January 4, 2015 [Page 4] Internet-Draft SIP Capability Indicators July 2014 sip.events sip.priority sip.methods sip.extensions sip.schemes sip.isfocus sip.message sip.ice sip.app-subtype sip.fax The following media feature tags from RFC 3840 [2], RFC 4235 [9] and RFC 5626 [10] are NOT considered to be useful to be defined as Feature-Capability indicators: sip.automata sip.class sip.mobility sip.actor sip.byeless sip.rendering sip.instance 4. Security Considerations The security considerations in RFC 3840 [2] and RFC 6809 [1] apply to the use of Feature-capability indicators in the SIP tree. 5. IANA Considerations This specification registers the following new feature-capability indicators in the SIP tree per the procedures defined in RFC 6809 [10]. 5.1. Audio Feature-capability indicator name: sip.audio ASN.1 Identifier: 1 Descrition: This Feature-capability indicator indicates that the intermediary supports audio as a streaming media type. Allen Expires January 4, 2015 [Page 5] Internet-Draft SIP Capability Indicators July 2014 Feature-capability indicator specification reference: RFC 3840 [2]. Additional information: Values appropriate for use with this Feature-Capability indicator: Boolean. This Feature-Capability indicator is most useful in a communications application for describing the capabilities of a network intermediary, such as an IP-PBX or conference bridge. Examples of typical use: An IP PBX indicating that it is capable of accepting and initiating sessions with audio as a streaming media type. Security Considerations: Security considerations for this Feature-capability indicator are discussed in RFC 6809 [1] and RFC 3840 [2]. 5.2. Application Feature-capability indicator name: sip.application ASN.1 Identifier: 2 Descrition: This Feature-capability indicator indicates that the intermediary supports application as a streaming media type. Feature-capability indicator specification reference: RFC 3840 [2]. Additional information: Values appropriate for use with this Feature-Capability indicator: Boolean. This Feature-Capability indicator is most useful in a communications application for describing the capabilities of a network intermediary, such as an IP-PBX or conference bridge. Examples of typical use: An IP PBX indicating that it is capable of accepting and initiating sessions with a media control application. Allen Expires January 4, 2015 [Page 6] Internet-Draft SIP Capability Indicators July 2014 Security Considerations: Security considerations for this Feature-capability indicator are discussed in RFC 6809 [1] and RFC 3840 [2]. 5.3. Data Feature-capability indicator name: sip.data ASN.1 Identifier: 1 Descrition: This Feature-capability indicator indicates that the intermediary supports data as a streaming media type. Feature-capability indicator specification reference: RFC 3840 [2]. Additional information: Values appropriate for use with this Feature-Capability indicator: Boolean. This Feature-Capability indicator is most useful in a communications application for describing the capabilities of a network intermediary, such as an IP-PBX or conference bridge. Examples of typical use: An IP PBX indicating that it is capable of accepting and initiating sessions with data as a streaming media type. Security Considerations: Security considerations for this Feature-capability indicator are discussed in RFC 6809 [1] and RFC 3840 [2]. 5.4. Control Feature-capability indicator name: sip.control ASN.1 Identifier: 4 Allen Expires January 4, 2015 [Page 7] Internet-Draft SIP Capability Indicators July 2014 Descrition: This Feature-capability indicator indicates that the intermediary supports control as a streaming media type. Feature-capability indicator specification reference: RFC 3840 [2]. Additional information: Values appropriate for use with this Feature-Capability indicator: Boolean. This Feature-Capability indicator is most useful in a communications application for describing the capabilities of a network intermediary, such as an IP-PBX or conference bridge. Examples of typical use: A conference bridge indicating that it is capable of supporting a floor control application. Security Considerations: Security considerations for this Feature-capability indicator are discussed in RFC 6809 [1] and RFC 3840 [2]. 5.5. Video Feature-capability indicator name: sip.video ASN.1 Identifier: 5 Descrition: This Feature-capability indicator indicates that the intermediary supports video as a streaming media type. Feature-capability indicator specification reference: RFC 3840 [2]. Additional information: Values appropriate for use with this Feature-Capability indicator: Boolean. This Feature-Capability indicator is most useful in a communications application for describing the capabilities of a network intermediary, such as an IP-PBX or conference bridge. Allen Expires January 4, 2015 [Page 8] Internet-Draft SIP Capability Indicators July 2014 Examples of typical use: An IP PBX indicating that it is capable of accepting and initiating sessions with video as a streaming media type. Security Considerations: Security considerations for this Feature-capability indicator are discussed in RFC 6809 [1] and RFC 3840 [2]. 5.6. Text Feature-capability indicator name: sip.text ASN.1 Identifier: 6 Descrition: This Feature-capability indicator indicates that the intermediary supports text as a streaming media type. Feature-capability indicator specification reference: RFC 3840 [2]. Additional information: Values appropriate for use with this Feature-Capability indicator: Boolean. This Feature-Capability indicator is most useful in a communications application for describing the capabilities of a network intermediary, such as an IP-PBX or conference bridge. Examples of typical use: An IP PBX indicating that it is capable of accepting and initiating sessions with text as a streaming media type. Security Considerations: Security considerations for this Feature-capability indicator are discussed in RFC 6809 [1] and RFC 3840 [2]. 5.7. Duplex Feature-capability indicator name: sip.duplex Allen Expires January 4, 2015 [Page 9] Internet-Draft SIP Capability Indicators July 2014 ASN.1 Identifier: 7 Descrition: The values of the sip.duplex (not the plurality) Feature- capability indicator indicate whether a intermediary can support sessions that simultaneously send and receive media ("full"), alternate between sending and receiving ("half"), can only receive ("receive-only") or only send ("send-only"). Feature-capability indicator specification reference: RFC 3840 [2]. Additional information: Values appropriate for use with this Feature-Capability indicator: Token with an equality relationship. Typical values include: full: The device can simultaneously send and receive media. half: The device can alternate between sending and receiving media. receive-only: The device can only receive media. send-only: The device can only send media. Note that a list of multiple values can be include (e.g. "full, half" indicating that both full duplex and half duplex communciations are supported). If "full" or "half" is indicated then support for "receive-only" and "send-only" sessions can also be assumed. This Feature-Capability indicator is most useful in a communications application for describing the capabilities of a network intermediary, such as an IP-PBX or conference bridge. Examples of typical use: A conference bridge indicating that it is capable of accepting sessions with half duplex communications (e.g. Push to Talk). Security Considerations: Security considerations for this Feature-capability indicator are discussed in RFC 6809 [1] and RFC 3840 [2]. Allen Expires January 4, 2015 [Page 10] Internet-Draft SIP Capability Indicators July 2014 5.8. Description Feature-capability indicator name: sip.description ASN.1 Identifier: 8 Descrition: This Feature-capability indicator provides a textual description of the intermediary. Feature-capability indicator specification reference: RFC 3840 [2]. Additional information: Values appropriate for use with this Feature-Capability indicator: String with an equality relationship. This Feature-Capability indicator is most useful in a communications application for describing the capabilities of a network intermediary, such as an IP-PBX or conference bridge. Examples of typical use: An IP PBX indicating that it is the IP PBX of example.org. Security Considerations: Security considerations for this Feature-capability indicator are discussed in RFC 6809 [1] and RFC 3840 [2]. 5.9. Event Packages Feature-capability indicator name: sip.events ASN.1 Identifier: 9 Descrition: Each value of the sip.events (note the plurality) Feature- capability indicator indicates a SIP event package RFC 6665 supported by a SIP UA. The values for this Feature-capability indicator equal the event package names that are registered by each event package. Feature-capability indicator specification reference: RFC 3840 [2]. Allen Expires January 4, 2015 [Page 11] Internet-Draft SIP Capability Indicators July 2014 Additional information: Values appropriate for use with this Feature-Capability indicator: Token with an equality relationship. Values are taken from the IANA SIP Event types namespace registry. This Feature-Capability indicator is most useful in a communications application for describing the capabilities of a network intermediary, such as an IP-PBX or conference bridge. Examples of typical use: An IP PBX indicating that it supports and can accept subscriptions to the message waiting event package, (i.e it is also the voicemail server). Security Considerations: Security considerations for this Feature-capability indicator are discussed in RFC 6809 [1] and RFC 3840 [2]. 5.10. Priority Feature-capability indicator name: sip.priority ASN.1 Identifier: 10 Descrition: This Feature-capability indicator indicates the call priorities the intermediary is willing to handle. A value of X means that the intermediary is willing to tak requests with priority X and higher. Feature-capability indicator specification reference: RFC 3840 [2]. Additional information: Values appropriate for use with this Feature-Capability indicator: An integer. Each integral value corresponds to one of the possible values of the Priority header field as specified in SIP. The mapping is defined as: non-urgent: Integral value of 10. The device supports non- urgent calls. normal: Integral value of 20. The device supports normal calls. Allen Expires January 4, 2015 [Page 12] Internet-Draft SIP Capability Indicators July 2014 urgent: Integral value of 30. The device supports urgent calls. emergency: Integral value of 40. The device supports calls in the case of an emergency situation. This Feature-Capability indicator is most useful in a communications application for describing the capabilities of a network intermediary, such as an IP-PBX or conference bridge. Examples of typical use: An IP PBX indicating that it accepts emergency calls (e.g. it can connect a user directly to campus security). Security Considerations: Security considerations for this Feature-capability indicator are discussed in RFC 6809 [1] and RFC 3840 [2]. 5.11. Methods Feature-capability indicator name: sip.methods ASN.1 Identifier: 11 Descrition: Each value of the sip.methods (note the plurality) Feature- capability indicator indicates a SIP method supported by this intermediary. In this case, "supported" means that the intermediary will accept requests with this method. In that sense, it has the same connotation as the Allow header field. Feature-capability indicator specification reference: RFC 3840 [2]. Additional information: Values appropriate for use with this Feature-Capability indicator: Token with an equality relationship. Values are taken from the Methods table defined in the IANA SIP parameters registry. This Feature-Capability indicator is most useful in a communications application for describing the capabilities of a network intermediary, such as an IP-PBX or conference bridge. Allen Expires January 4, 2015 [Page 13] Internet-Draft SIP Capability Indicators July 2014 Examples of typical use: An IP PBX indicating that it accepts a REFER request to transfer the session. Security Considerations: Security considerations for this Feature-capability indicator are discussed in RFC 6809 [1] and RFC 3840 [2]. 5.12. Extensions Feature-capability indicator name: sip.extensions ASN.1 Identifier: 12 Descrition: Each value of the sip.extensions (note the plurality) Feature- capability indicator indicates is a SIP extension (each of which is defined by an option-tag registered with IANA) that is understood by the intermediary. Understood, in this context, means the same as if the option tag had been included in a Supported header field. Feature-capability indicator specification reference: RFC 3840 [2]. Additional information: Values appropriate for use with this Feature-Capability indicator: Token with an equality relationship. Values are taken from the option tags table in the IANA SIP parameters registry. This Feature-Capability indicator is most useful in a communications application for describing the capabilities of a network intermediary, such as an IP-PBX or conference bridge. Examples of typical use: An IP PBX indicating that it supports the target dialog extension for use with a session transfer. Security Considerations: Security considerations for this Feature-capability indicator are discussed in RFC 6809 [1] and RFC 3840 [2]. Allen Expires January 4, 2015 [Page 14] Internet-Draft SIP Capability Indicators July 2014 5.13. Schemes Feature-capability indicator name: sip.schemes ASN.1 Identifier: 13 Descrition: Each value of the sip.schemes (note the plurality) Feature- capability indicator indicates a URI scheme that is supported by an intermediary. Supported implies, for example, that the intermediary would know how to handle a URI of that scheme in the Contact header field of a redirect response. Feature-capability indicator specification reference: RFC 3840 [2]. Additional information: Values appropriate for use with this Feature-Capability indicator: Token with an equality relationship. Values are taken from the IANA URI scheme registry. This Feature-Capability indicator is most useful in a communications application for describing the capabilities of a network intermediary, such as an IP-PBX or conference bridge. Examples of typical use: An IP PBX indicating that it will accept redirection of the session to a server that supports media content (e.g a music server). Security Considerations: Security considerations for this Feature-capability indicator are discussed in RFC 6809 [1] and RFC 3840 [2]. 5.14. Is Focus Feature-capability indicator name: sip.isfocus ASN.1 Identifier: 14 Descrition: This Feature-capability indicator indicates that the intermediary is a conference server, also known as a focus, and is capable of mixing together the media for all calls to the same URI. Allen Expires January 4, 2015 [Page 15] Internet-Draft SIP Capability Indicators July 2014 Feature-capability indicator specification reference: RFC 3840 [2]. Additional information: Values appropriate for use with this Feature-Capability indicator: Boolean. This Feature-Capability indicator is most useful in a communications application for describing the capabilities of a network intermediary, such as a conference bridge. Examples of typical use: A conference bridge indicating that it is a conference bridge and is capable of acting as a conference focus for this session. Security Considerations: Security considerations for this Feature-capability indicator are discussed in RFC 6809 [1] and RFC 3840 [2]. 5.15. Message Feature-capability indicator name: sip.message ASN.1 Identifier: 15 Descrition: This Feature-capability indicator indicates that the intermediary supports message as a streaming media type. Feature-capability indicator specification reference: RFC 4569 [3]. Additional information: Values appropriate for use with this Feature-Capability indicator: Boolean. This Feature-Capability indicator is most useful in a communications application for describing the capabilities of a network intermediary, such as an IP-PBX or conference bridge. Examples of typical use: An IP PBX indicating that it is capable of accepting and initiating sessions with message as a streaming media type. Allen Expires January 4, 2015 [Page 16] Internet-Draft SIP Capability Indicators July 2014 Security Considerations: Security considerations for this Feature-capability indicator are discussed in RFC 6809 [1], RFC 3840 [2] and RFC 4569 [3]. 5.16. Interactive Connectivity Establishment Feature-capability indicator name: sip.ice ASN.1 Identifier: 16 Descrition: This Feature-capability indicator indicates that the intermediary supports that the device supports Interactive Connectivity Establishment (ICE). Feature-capability indicator specification reference: RFC 5768 [4]. Additional information: Values appropriate for use with this Feature-Capability indicator: Boolean. This Feature-Capability indicator is most useful in a communications application for describing the capabilities of a network intermediary, such as an IP-PBX or conference bridge. Examples of typical use: An IP PBX indicating that it is capable of using ICE to establish media connectivity for sessions. Security Considerations: Security considerations for this Feature-capability indicator are discussed in RFC 6809 [1], RFC 3840 [2] and RFC 5768 [4]. 5.17. Application Subtype Feature-capability indicator name: sip.app-subtype ASN.1 Identifier: 17 Descrition: Allen Expires January 4, 2015 [Page 17] Internet-Draft SIP Capability Indicators July 2014 This Feature-capability indicator indicates the MIME application subtypes supported by the intermediary for purposes of streaming media. Feature-capability indicator specification reference: RFC 5688 [5]. Additional information: Values appropriate for use with this Feature-Capability indicator: Token (equality relationship). This Feature-Capability indicator is most useful in a communications application for describing the capabilities of a network intermediary, such as an IP-PBX or conference bridge. Examples of typical use: A conference setrver indicating that it supports an application specific media burst control protocol for Push to Talk sessions. Security Considerations: Security considerations for this Feature-capability indicator are discussed in RFC 6809 [1], RFC 3840 [2] and RFC 5688 [5]. 5.18. Fax Feature-capability indicator name: sip.fax ASN.1 Identifier: 18 Descrition: This Feature-capability indicator indicates whether an intermediary accepts sessions using the ITU-T T.38 [11] fax protocol ("t38") or the passthrough method of fax transmission using the ITU-T G.711 [12] audio codec ("passthrough"). Feature-capability indicator specification reference: RFC 6913 [6]. Additional information: Values appropriate for use with this Feature-Capability indicator: Token with an equality relationship. Values are: Allen Expires January 4, 2015 [Page 18] Internet-Draft SIP Capability Indicators July 2014 t38: The device supports the "image/t38" media type (RFC 3326) [13] and implements ITU-T T.38 [11] for transporting the ITU-T T.30 [14] and ITU-T T.4 [15] fax data over IP. passthrough: The device supports the "audio/pcmu" and "audio/ pcma" media types (RFC4856) [16] for transporting ITU-T T.30 [14] and ITU-T T.4 [15] fax data using the ITU-T G.711 [12] audio codec. This Feature-Capability indicator is most useful in a communications application for describing the capabilities of a network intermediary, such as an IP-PBX or conference bridge. Examples of typical use: A conference bridge indicating that it is capable of distributing T.38 fax media to the participants in a conference. Security Considerations: Security considerations for this Feature-capability indicator are discussed in RFC 6809 [1], RFC 3840 [2] and RFC 6913 [6]. 6. Acknowledgements This document draws heavily on text from the earlier work on RFC 6809 [1], RFC 3840 [2], RFC 4569 [3], RFC 5768 [4], RFC 5688 [5] and RFC 6913 [6]. The author would like to thank the authors of these RFCs: Christer Holmber, Ivo Sedlacek, Hadriel Kaplan, Jonathan Rosenberg Henning Schulzrinne, Paul Kyzivat, Gonzalo Camarillo, D Hanes, G Salgueiro and K Fleming for their earlier work which has made this a relatively simple IANA registration exercise. 7. References 7.1. Normative References [1] Holmberg, C., Sedlacek, I., and H. Kaplan, "Mechanism to Indicate Support of Features and Capabilities in the Session Initiation Protocol (SIP)", RFC 6809, November 2012. [2] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, "Indicating User Agent Capabilities in the Session Initiation Protocol (SIP)", RFC 3840, August 2004. [3] Camarillo, G., "Internet Assigned Number Authority (IANA) Registration of the Message Media Feature Tag", RFC 4569, Allen Expires January 4, 2015 [Page 19] Internet-Draft SIP Capability Indicators July 2014 July 2006. [4] Rosenberg, J., "Indicating Support for Interactive Connectivity Establishment (ICE) in the Session Initiation Protocol (SIP)", RFC 5768, April 2010. [5] Rosenberg, J., "A Session Initiation Protocol (SIP) Media Feature Tag for MIME Application Subtypes", RFC 5688, January 2010. [6] Hanes, D., Salgueiro, G., and K. Fleming, "Indicating Fax over IP Capability in the Session Initiation Protocol (SIP)", RFC 6913, March 2013. [7] Roach, A., "SIP-Specific Event Notification", RFC 6665, July 2012. 7.2. Informative References [8] Rosenberg, J., "Request Authorization through Dialog Identification in the Session Initiation Protocol (SIP)", RFC 4538, June 2006. [9] Rosenberg, J., Schulzrinne, H., and R. Mahy, "An INVITE- Initiated Dialog Event Package for the Session Initiation Protocol (SIP)", RFC 4235, November 2005. [10] Jennings, C., Mahy, R., and F. Audet, "Managing Client- Initiated Connections in the Session Initiation Protocol (SIP)", RFC 5626, October 2009. [11] International Telecommunication Union, "Procedures for real- time Group 3 facsimile communication over IP Networks", ITU- T Recommendation T.38, October 2010. [12] International Telephone and Telegraph Consultative Committee, "Pulse Code Modulation (PCM) of Voice Frequencies", CCITT Recommendation G.711, 1972. [13] Schulzrinne, H., Oran, D., and G. Camarillo, "The Reason Header Field for the Session Initiation Protocol (SIP)", RFC 3326, December 2002. [14] International Telecommunication Union, "Procedures for document facsimile transmission in the general switched telephone network", ITU-T Recommendation T.30, September 2005. [15] International Telecommunication Union, "Standardization of Allen Expires January 4, 2015 [Page 20] Internet-Draft SIP Capability Indicators July 2014 Group 3 facsimile terminals for document transmission", ITU- T Recommendation T.4, July 2003. [16] Casner, S., "Media Type Registration of Payload Formats in the RTP Profile for Audio and Video Conferences", RFC 4856, February 2007. Author's Address Andrew Allen (editor) Blackberry 1200 Sawgrass Corporate Parkway Sunrise, Florida 33323 USA Email: aallen@blackberry.com Allen Expires January 4, 2015 [Page 21]