Network Working Group H. Schulzrinne
Internet-Draft Columbia U.
Expires: August 30, 2004 March 2004
is-composing Indication for Instant Messaging Using the Session
Initiation Protocol (SIP)
draft-ietf-simple-iscomposing-00
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
In instant messaging systems, it is useful to know that the other
party is composing a message, e.g., typing. This document defines a
new content type and XML namespace that conveys information about a
message being composed. The message could be of any type, including
text, voice or video.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology and Conventions . . . . . . . . . . . . . . . . . 3
3. Description . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Using the Indicator . . . . . . . . . . . . . . . . . . . . . 5
5. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
6. XML Schema Definitions . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8.1 Content-Type Registration for
'application/sip-iscomposing+xml' . . . . . . . . . . . . 6
8.2 URN Sub-Namespace Registration for
'urn:ietf:params:xml:ns:sip-iscomposing' . . . . . . . . . 7
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1 Normative References . . . . . . . . . . . . . . . . . . . . 8
10.2 Informative References . . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 9
Intellectual Property and Copyright Statements . . . . . . . . 10
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1. Introduction
By definition, instant messaging is message-based, i.e., a user
composes a message by typing, speaking or recording a video clip.
This message is then sent. Unlike email, instant messaging is often
conversational, so that the other party is waiting for a response.
If no response is forthcoming, an IM session participant may
erroneously assume that either the communication partner has left or
that it is her turn to type again, leading to messaging "crossing on
the wire".
To avoid this uncertainty, a number of commercial instant messaging
systems feature an "is-typing" indication that is set as soon as one
party starts typing a message. In this document, we describe a
generalized version of this indication. A status message is
delivered to the IM recipient in the same manner as the messages
themselves. The is-composing 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 IM user states in the future.
This indication 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
[I-D.ietf-impp-cpim-pidf], 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
gateway into non-SIP systems.
The mechanism described here aims to satisfy the requirements in
[I-D.rosenberg-simple-messaging-requirements].
2. Terminology and Conventions
This memo makes use of the vocabulary defined in the IMPP Model
document [RFC2778]. Terms such as CLOSED, INSTANT MESSAGE, OPEN,
PRESENCE SERVICE, PRESENTITY, WATCHER, and WATCHER USER AGENT in the
memo are 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
XX, RFC 2119 [RFC2119].
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3. Description
We model user behavior as states, initially limited to Idle and
Active. When the user first starts composing, the state becomes
Active and an isComposing message containing a
See RFCXXXX.