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SIMPLE
Instant messaging (IM) and presence
A standard instant messaging protocol based on SIP, called SIMPLE, has been
proposed and is under development. SIMPLE can also carry presence information,
conveying a person's willingness and ability to engage in communications.
Presence information is most recognizable today as buddy status in IM clients
such as Yahoo! Messenger, AIM, Skype, or the open standard Jabber.
Some efforts have been made to integrate SIP-based VoIP with the XMPP
specification used by Jabber. Most notably Google Talk, which extends XMPP to
support voice, plans to integrate SIP. Google's XMPP extension is called Jingle
and, like SIP, it acts as a Session Description Protocol carrier.
The free OpenWengo softphone and the proprietary Gizmo Project have implemented
SIP in their clients and services. As both software use SIP they can accept
calls from each other.
SIP itself defines a method of passing instant messages between endpoints,
similar to SMS messages. This is not generally supported by commercial
operators, but UK-based VoIP provider AQL supports this method of communication,
including the sending of such messages to ordinary GSM mobile telephones.
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