Network Working Group H. Schulzrinne Internet-Draft Columbia U. Expires: February 8, 2005 August 10, 2004 Indication of Message Composition for Instant Messaging draft-ietf-simple-iscomposing-03 Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. 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. This Internet-Draft will expire on February 8, 2005. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract In instant messaging (IM) systems, it is useful to know during an IM conversation that the other party is composing a message, e.g., typing or recording an audio message. This document defines a new status message content type and XML namespace that conveys information about a message being composed. The status message can indicate the composition of a message of any type, including text, voice or video. The status messages are delivered to the instant messaging recipient in the same manner as the instant messages themselves. Schulzrinne Expires February 8, 2005 [Page 1] Internet-Draft iscomposing August 2004 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology and Conventions . . . . . . . . . . . . . . . . . 3 3. Description . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.2 Message Composer Behavior . . . . . . . . . . . . . . . . 4 3.3 Status Message Receiver Behavior . . . . . . . . . . . . . 6 3.4 Message Content . . . . . . . . . . . . . . . . . . . . . 7 3.5 Additional Status Information . . . . . . . . . . . . . . 7 4. Using the Status Message . . . . . . . . . . . . . . . . . . . 8 5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 6. XML Document Format . . . . . . . . . . . . . . . . . . . . . 9 6.1 XML Schema . . . . . . . . . . . . . . . . . . . . . . . . 9 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 8.1 Content-Type Registration for 'application/im-iscomposing+xml' . . . . . . . . . . . . . 10 8.2 URN Sub-Namespace Registration for 'urn:ietf:params:xml:ns:im-iscomposing' . . . . . . . . . 11 8.3 Schema registration . . . . . . . . . . . . . . . . . . . 11 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 10.1 Normative References . . . . . . . . . . . . . . . . . . . . 12 10.2 Informative References . . . . . . . . . . . . . . . . . . . 12 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 13 Intellectual Property and Copyright Statements . . . . . . . . 14 Schulzrinne Expires February 8, 2005 [Page 2] Internet-Draft iscomposing August 2004 1. Introduction By definition, instant messaging (IM) is message-based: a user composes a message by, for example, typing, speaking or recording a video clip. This message is then sent to one or more recipients. Unlike email, instant messaging is often conversational, so that the other party is waiting for a response. If no response is forthcoming, a participant in an instant messaging conversation may erroneously assume that either the communication partner has left or that it is her turn to type again, leading to two messages "crossing on the wire". To avoid this uncertainty, a number of commercial instant messaging systems feature an "is-typing" indication that is sent as soon as one party starts typing a message. In this document, we describe a generalized version of this indication, called isComposing status message. As described in Section 3 in more detail, a status message is delivered to the instant message recipient in the same manner as the messages themselves. The isComposing status messages can announce the composition of any media type, not just text. For example, it might be used if somebody is recording an audio or video clip. In addition, it can be extended to convey other instant messaging user states in the future. Below, we will call these messages "status messages" for brevity. The status messages are carried as XML, as instances of the XML schema defined in Section 6 and labeled as an application/ im-iscomposing+xml content type. These status messages can be considered somewhat analogous to the comfort noise packets that are transmitted in silence-suppressed interactive voice conversations. Events and extensions to presence, such as PIDF [7], were also considered, but have a number of disadvantages. They add more overhead, since an explicit and periodic subscription is required. For page-mode delivery, subscribing to the right user agent and set of messages may not be easy. An in-band, message-based mechanism is also easier to translate across heterogeneous instant messaging systems. The mechanism described here aims to satisfy the requirements in [8]. 2. Terminology and Conventions This memo makes use of the vocabulary defined in the IMPP Model document [1]. Terms such as CLOSED, INSTANT MESSAGE, OPEN, PRESENCE SERVICE, PRESENTITY, WATCHER, and WATCHER USER AGENT in this memo are Schulzrinne Expires February 8, 2005 [Page 3] Internet-Draft iscomposing August 2004 used in the same meaning as defined therein. The key words MUST, MUST NOT, REQUIRED, SHOULD, SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL in this document are to be interpreted as described in BCP 14, RFC 2119 [2]. This document discusses two kinds of messages, namely the instant message (IM) conveying actual content between two or more users engaged in an instant messaging conversation, and the status message, described in this document, that indicates the current composing status to the other participants in a conversation. We use the terms "content message" and "status message" for these two message types. 3. Description 3.1 Overview We model the user of an instant messaging system as being in one of several states, in this draft limited to "idle" and "active". By default, the user is in "idle" state, both before starting to compose a message and after sending it. 3.2 Message Composer Behavior Only the instant messaging user agent actively composing a content message generates status messages indicating the current state. When the user first starts composing a content message (the actual instant message), the state becomes "active" and an isComposing status message containing a element indicating "active" is sent to the recipient of the content message being composed. As long as the user continues to produce instant message content, the user remains in state "active". There are two sender timers, the active-state refresh interval and the idle time-out interval. The active-state refresh interval determines how often "active" state messages are sent while the composer remains in "active" state. The interval is chosen by the composing user and indicated in the element in the status message, expressed in integer seconds. Each transmission of the isComposing message resets the timer. The interval SHOULD be no shorter than 60 seconds. A message composer MAY decide not to send active-state refresh messages at all. It indicates that by omitting the refresh interval; this will cause the receiver to assume that it has gone idle after 120 seconds. (In most cases, the content message will have been sent by then.) No refresh messages are sent in "idle" state. Schulzrinne Expires February 8, 2005 [Page 4] Internet-Draft iscomposing August 2004 The active-state refresh mechanism deals with the case that the user logs off or the application crashes before the content message is completed. If the user stops composing for more than a configured time interval, the idle timeout, the state transitions to "idle" and an "idle" status message is sent. When the user starts composing again while in "idle" state, the state transitions to "active", with the corresponding status message being sent. Unless otherwise configured by the user, the idle timeout SHOULD have a default value of 15 seconds. If a content message is sent before the idle threshold expires, no "idle" state indication is needed. Thus, in most cases, only one status message is generated for each content message. In any event, the message rate is limited to one status message per refresh threshold interval. The state transitions are shown in Figure 1. +-------------+ |+-----------+| || || +------>| idle |<--------+ | || || | | |+-----------+| | | +------+------+ | content | | | idle timeout msg. sent | | composing | w/o activity ----------- | | ------------- | ------------------ -- | | "active" msg. | "idle" status msg. | | | | +------V------+ | | | | | | | | | | | | | +------+ active +--------+ | | | |------+ +------^------+ | refresh timeout | | -------------------- | | "active" status msg. +-------------+ Sender state diagram Schulzrinne Expires February 8, 2005 [Page 5] Internet-Draft iscomposing August 2004 Figure 1 3.3 Status Message Receiver Behavior The status message receiver uses the status messages to determine the state of the content message sender. If the most recent "active" status message contained a value, the refresh time-out is set to that value; it is 120 seconds otherwise. The state at the receiver transitions from "active" to "idle" under three conditions: 1. A status message with status "idle" is received. 2. A content message is received. 3. The refresh interval expires. Receivers MUST be able to handle multiple consecutive isComposing messages with "active" state regardless of the refresh interval. The state transitions are shown in Figure 2. +-------------+ |+-----------+| || || +------>| idle |<------+ | || || | | |+-----------+| | | +------+------+ | | | | "idle" recd. | |"active" msg.| refresh timeout or content recd. | | | or 120s | | | | +------V------+ | | | | | | | | | | | | | +------+ active +------+ | | | | +-------------+ Receiver state diagram Figure 2 Schulzrinne Expires February 8, 2005 [Page 6] Internet-Draft iscomposing August 2004 3.4 Message Content We briefly describe the message content to summarize the discussion above. This description is non-normative. The schema (Section 6) should be consulted for the normative message format. The message consists of an element, with a mandatory element indicating the composer state, i.e., idle or active. In addition, there are three optional elements, , indicating the time of last activity, , the type of message being created, and , the time interval after which the receiver can expect an update from the composer. Details are given in the following section. 3.5 Additional Status Information The status message contains additional optional elements to provide further details on the composition activity. All of these can appear in both "active" and "idle" state messages. The optional element describes the absolute time when the user last added or edited content. The optional element indicates what type of media the messaging terminal is currently composing. It can contain either just a MIME media type, such as "audio" or "text", or a media type and subtype, such as "text/html". It is best understood as a hint to the user, not a guarantee that the actual content message will indeed contain only the content indicated. It allows the human recipient to be prepared for the likely message format. In order to further describe message composition, the XML schema or the set of allowable state names can be extended in future documents. Recipients of status messages implementing this specification without extensions MUST treat state tokens other than "idle" and "active" as "idle". Additional elements MUST use their own namespaces and MUST be designed such that receivers can safely ignore such extensions. Adding elements to the namespace defined in this document is not permitted. The isComposing status message MAY be carried in CPIM messages [3]. Such a wrapper is particularly useful if messages are relayed by a conference server since the CPIM message maintains the identity of the original composer. Schulzrinne Expires February 8, 2005 [Page 7] Internet-Draft iscomposing August 2004 4. Using the Status Message The isComposing status message can be used with either page mode or session mode, although it is a more natural fit with session mode. In session mode, the status message is sent as part of the messaging stream. Its usage is negotiated just like any other media type in that stream, with details depending on the session mode protocol. Sending the status messages within the session-mode messaging stream has at least three benefits. First, it ensures proper ordering and synchronization with the actual content messages being composed. In messaging systems that guarantee in-order delivery of messages, this approach avoids that message reordering across two delivery mechanisms has an active indication appear at the receiver after the actual message has been delivered. Secondly, end-to-end security can be applied to the messages. Thirdly, session negotiation mechanisms can be used to turn it on and off at any time, and even negotiate its use in a single direction at a time. Usage with page mode is also straightforward. There, the status message is carried as the body of a page mode message. In SIP-based IM, The composer MUST cease transmitting status messages if the receiver returned a 415 status code (Unsupported Media Type) in response to a MESSAGE request containing the status indication. The sender cannot be assured that the status message gets delivered before the actual content being composed arrives. However, SIP page mode is limited to one unacknowledged message, so that out-of-order delivery is unlikely, albeit still possible if proxies are involved. 5. Examples active text/plain 90 Schulzrinne Expires February 8, 2005 [Page 8] Internet-Draft iscomposing August 2004 idle 2003-01-27T10:43:00Z audio 6. XML Document Format An isComposing document is an XML document that MUST be well-formed and SHOULD be valid. isComposing documents MUST be based on XML 1.0 and MUST be encoded using UTF-8. This specification makes use of XML namespaces for identifying isComposing documents. The namespace URI for elements defined for this purpose is a URN, using the namespace identifier 'ietf'. This URN is: urn:ietf:params:xml:ns:im-iscomposing 6.1 XML Schema Schulzrinne Expires February 8, 2005 [Page 9] Internet-Draft iscomposing August 2004 7. Security Considerations The isComposing indication provides a fine-grained view of the activity of the entity composing and thus deserves particularly careful confidentiality protection so that only the intended destination of the message will receive the isComposing indication. Since the status messages are carried using the IM protocol itself, all security considerations of the underlying IM protocol apply also to the isComposing status messages. There are potential privacy issues in sending isComposing status messages before an actual conversation has been established between the communicating users. A status message may be sent even if the user later abandons the message. It is RECOMMENDED that isComposing indications in page-mode are only sent when a message is being composed as a reply to an earlier message. This document does not prescribe how an implementation detects in page mode whether a message is in response to an earlier one, but elapsed time or user interface behavior might be used as hints. 8. IANA Considerations 8.1 Content-Type Registration for 'application/im-iscomposing+xml' To: ietf-types@iana.org Subject: Registration of MIME media type application/ im-iscomposing+xml MIME media type name: application MIME subtype name: im-iscomposing+xml Required parameters: (none) Optional parameters: charset; Indicates the character encoding of enclosed XML. Default is UTF-8. Encoding considerations: Uses XML, which can employ 8-bit characters, depending on the character encoding used. See RFC 3023 [4], section 3.2. Security considerations: This content type is designed to carry information about current user activity, which may be considered private information. Appropriate precautions should be adopted to limit disclosure of this information. Interoperability considerations: This content type provides a common format for exchange of composition activity information. Published specification: XXXX (this document) Applications which use this media type: Instant messaging systems. Additional information: none Schulzrinne Expires February 8, 2005 [Page 10] Internet-Draft iscomposing August 2004 Person & email address to contact for further information: Henning Schulzrinne, hgs@cs.columbia.edu Intended usage: LIMITED USE Author/Change controller: This specification is a work item of the IETF SIMPLE working group, with mailing list address simple@ietf.org. Other information: This media type is a specialization of application/xml RFC 3023 [4], and many of the considerations described there also apply to application/im-iscomposing+xml. 8.2 URN Sub-Namespace Registration for 'urn:ietf:params:xml:ns:im-iscomposing' URI: urn:ietf:params:xml:ns:im-iscomposing Description: This is the XML namespace for XML elements defined by RFCXXXX to describe composition activity by an instant messaging client using the application/im-iscomposing+xml content type. Registrant Contact: IETF, SIMPLE working group, simple@ietf.org, Henning Schulzrinne, hgs@cs.columbia.edu XML: BEGIN Is-composing Indication for Instant Messaging

Namespace for SIMPLE iscomposing extension

urn:ietf:params:xml:ns:im-composing

See RFCXXXX.

END 8.3 Schema registration This section registers a new XML schema per the procedures in [5]. URI: urn:ietf:params:xml:schema:im-composing Schulzrinne Expires February 8, 2005 [Page 11] Internet-Draft iscomposing August 2004 Registrant Contact: IETF, SIMPLE working group, (simple@ietf.org), Henning Schulzrinne (hgs@cs.columbia.edu). The XML for this schema can be found as the sole content of Section 6.1. 9. Acknowledgements Ben Campbell, Miguel Garcia, Scott Hollenbeck, Christian Jansson, Cullen Jennings, Hisham Khartabil, Allison Mankin, Aki Niemi, Jonathan Rosenberg and Xiaotao Wu provided helpful comments. 10. References 10.1 Normative References [1] Day, M., Rosenberg, J. and H. Sugano, "A Model for Presence and Instant Messaging", RFC 2778, February 2000. [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [3] Atkins, D. and G. Klyne, "Common Presence and Instant Messaging: Message Format", draft-ietf-impp-cpim-msgfmt-08 (work in progress), January 2003. [4] Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC 3023, January 2001. [5] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, January 2004. [6] Handley, M. and V. Jacobson, "SDP: Session Description Protocol", RFC 2327, April 1998. 10.2 Informative References [7] Sugano, H. and S. Fujimoto, "Presence Information Data Format (PIDF)", draft-ietf-impp-cpim-pidf-08 (work in progress), May 2003. [8] Rosenberg, J., "Advanced Instant Messaging Requirements for the Session Initiation Protocol (SIP)", draft-rosenberg-simple-messaging-requirements-01 (work in progress), February 2004. Schulzrinne Expires February 8, 2005 [Page 12] Internet-Draft iscomposing August 2004 Author's Address Henning Schulzrinne Columbia University Department of Computer Science 450 Computer Science Building New York, NY 10027 US Phone: +1 212 939 7004 EMail: hgs@cs.columbia.edu URI: http://www.cs.columbia.edu/~hgs Schulzrinne Expires February 8, 2005 [Page 13] Internet-Draft iscomposing August 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the IETF's procedures with respect to rights in IETF Documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM 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. Copyright Statement Copyright (C) The Internet Society (2004). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Schulzrinne Expires February 8, 2005 [Page 14]