Google has put its weight behind the open Extensible Messaging and Presence Protocol (XMPP), which defines how multi-media apps can be run over instant messaging.

Google has decided to contribute to XMPP extensions that will enable IM applications to conduct sessions involving voice and video.

The effort is spearheaded by the non-profit Jabber Software Foundation (JSF), which published initial documentation late last week. The extensions will be called Jingle.

The story goes that when the JSF began defining the Jingle set of extensions, it discovered that they were similar to the protocol used in the Google Talk IM application, so the two decided to collaborate to merge the technologies.

This is an important step forward, claims analyst Michael Osterman, because IM providers will eventually have to adopt open standards, and the confluence of VoIP and IM is getting great interest from users. "It's an important step forward in the right direction. It won't change the world overnight but it's something the industry will have to move towards," he said.

Google Talk is built on XMPP, unlike competing and older IM systems from AOL,Microsoft and Yahoo, all of which are based on proprietary technology.

By building its IM application on an open platform, Google took a significant stand on the side of interoperability, the main inconvenience affecting users of AOL's AIM, Microsoft's MSN Messenger and Yahoo Messenger. These three have been reluctant to link their IM networks for a variety of reasons, including concern over potential security breaches and worry of diluting the value for their advertisers if their audiences are no longer captive.

However, analysts say, if Google Talk can draw a critical mass of users, and offer them interoperability with other IM networks that support XMPP, it could present a real challenge.