IBM's Sametime has gained interoperability with public instant messaging networks from AOL and Google, and will interoperate with the one from Yahoo in a matter of weeks.

IBM made the announcement on Wednesday, almost a year after disclosing its intention to provide this interoperability for Sametime 7.5, the newest version of the enterprise IM system.

The gaping hole in the announcement is Microsoft's Windows Live Messenger, which, with AOL's AIM and Yahoo Messenger, is one the world's three largest consumer IM networks.

Microsoft sells an enterprise IM system called Live Communications Server (LCS) that competes directly with Sametime. LCS interoperates with AIM, Yahoo Messenger and Windows Live Messenger.

Akiba Saeedi, program director for Real Time Collaboration products at IBM's Lotus division, declined to comment on why Windows Live Messenger is missing from the Sametime interoperability picture.

The Sametime interoperability comes via a separate gateway server to which connectors for each IM network can be added at no extra cost beyond the price of the Sametime license, Saeedi said.

The gateway server provides a variety of management capabilities for IT departments to establish user policies and access rights and in general have control over the IM communications employees engage in with people on the Yahoo, AOL and Google networks.

Initially, the interoperability will be limited to exchanging text messages, but IBM wants to expand and deepen it to include other types of communications that have become common in IM services, like voice and video chats, file sharing and Web conferencing.

Instant messaging has in recent years become an essential tool in the workplace, so opening Sametime up to these external IM networks will allow its users to communicate with clients and partners who use AIM, Yahoo Messenger and Google Talk for business, Saeedi said.