R. Mahy Internet Draft Cisco Systems Document: draft-mahy-sip-cc-uri-params-00.txt November 2001 Expires: May 2002 URI Parameters for SIP Call Control Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 [RFC2026]. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. 1. Abstract This document specifies a way for SIP User Agents to convey information about participants in SIP calls and conversation spaces. This information allows other UAs to act more intelligently and autonomously and prevent call control feature interaction problems. 2. Conventions used in this document 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. Overview This document describes new parameters in [SIP] URLs which can be used in the Contact header, Accept-Contact, and Reject-Contact headers defined in [caller-prefs], or in other SIP URLs used to describe the unique characteristics of a contact (for example: [call-package], or SIP for [presence]). These parameters can be used to make intelligent decisions automatically to prevent call control feature interaction problems. For example, to prevent two send-only automatons from spewing media at each other. A more Mahy Expires: May 2002 1 URI Parameters for SIP Call Control detailed desription of the motivation for this work is desribed in [cc-models]. 4. Conveying Call Control Attributes in the Contact Header This specification extends the Contact , Accept-Contact, and Reject- Contact headers by adding the following URI parameters. A User Agent which supports these extensions MAY include them in a Contact header during registration. A UA which also supports [caller-prefs] MAY include these extensions in Accept-Contact or Reject-Contact headers. A UA which supports the call package SHOULD include the participation and user parameters for conversation space participants in call package notification bodies. 4.1. Visibility Attribute This attribute conveys if a UA wishes to be visible among the list of participants in the conversation space correpsonding to the current call-leg. [Obviously a UA that wishes to remain hidden SHOULD only establish call-legs with other UAs that will respect that desire.] A UA which supports this attribute SHOULD NOT reveal the existance of hidden participants to others. For example, a UA SHOULD NOT include hidden participants in a list of participants provided by call package. A UA MAY reveal hidden information to a class of special users (administrator for example) via call package. The default value for this attribute is "visible" Syntax: "visibility" "=" <"> ( "visible" | "hidden" ) <"> Default: visibility="visible" Examples: Contact: sip:recording-service@bank.com;visibility="hidden" Contact: sip:join-leave-announcer@conferences.com ;visibility="hidden" 4.2. Participation Attribute This attribute conveys if a participant is capable of terminating a session/call/conversation on its own (active) or not (passive), or will not contribute any unique content (none) as in the case of a relay, transcoder, or mixer. The default value for this attribute is "active" Syntax: "participation" "=" <"> ( "active" | "passive" | "none" ) <"> Mahy Expires: May 2002 2 URI Parameters for SIP Call Control Default: participation="active" Examples: Contact: sip:announcement25@server.org;participation="passive" Contact: sip:adhoc123245@conf.domain.com;participation="none" Contact: sip:call4524@relay12.relaysrus.net ;participation="none" 4.3. Type of User Attribute This attribute conveys if the user is a human or machine/robot/automaton. The default value for this attribute is "unknown". This is Syntax: "user" = <"> ( "human" | "automaton" | "unknown") <"> Default: user="unknown" Examples: Contact: sip:rmahy@voicemail.com;user=automaton Contact: sip:rohan@phone.cisco.com;user=human 5. Formal Syntax The following syntax specification uses the augmented Backus-Naur Form (BNF) as described in RFC-2234 [BNF]. This specification adds the following extension parameters to the Contact, Accept-Contact, and Reject-Contact header fields. These extension parameters MAY also be used extension parameters in a generic SIP URL. cc-uri-params = visibility | participation | user visibility = "visibility" "=" <"> ( "visible" | "hidden" ) <"> user = "user" = <"> ( "human" | "automaton" | "unknown") <"> participation = "participation" "=" <"> ( "active" | "passive" | "none" ) <"> 6. Security Considerations This extension may convey possibly private information such as the hidden or visible status of a participant within a conversation space. For obvious reasons, this information should only be shared with trusted parties. In addition, UAs are encouraged to encrypt, authenticate, and integrity check this information using general purpose mechanisms. Mahy Expires: May 2002 3 8. References [SIP] M. Handley, E. Schooler, and H. Schulzrinne, "SIP: Session Initiation Protocol", RFC2543, Internet Engineering Task Force, Nov 1998. [cc-model] R. Mahy, "A Call Control Model for SIP", Internet Draft , IETF, Nov. 2001. Work in Progress. [caller-prefs] J. Rosenberg, H. Schulzrinne, "SIP Caller Preferences and Callee Capabilities", Internet Draft , IETF, June 2001. Work in progress. [call-package] J. Rosenberg, H. Schulzrinne, "SIP Event Packages for Call Leg and Conference State", Internet Draft , IETF, July 2001. Work in Progress. [RFC2026] S Bradner, "The Internet Standards Process -- Revision 3", RFC2026 (BCP), IETF, October 1996. [RFC2119] S. Bradner, "Key words for use in RFCs to indicate requirement levels," Request for Comments (Best Current Practice) 2119, Internet Engineering Task Force, Mar. 1997. [BNF] D Crocker, P Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC2234, IETF, Nov 1997. 10. Acknowledgments Thanks to Jonathan Rosenberg and Henning Schulzrinne for their work on the call package and caller preferences. Without their prior work, this document would not have been relevant. 11. Author's Addresses Rohan Mahy Cisco Systems 170 West Tasman Dr, MS: SJC-21/3/3 Phone: +1 408 526 8570 Email: rohan@cisco.com Full Copyright Statement "Copyright (C) The Internet Society (date). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implmentation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph Mahy Expires: May 2002 4 URI Parameters for SIP Call Control are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Mahy Expires: May 2002 5