Google has finished making its Google Talk instant messaging service fully interoperable with IM networks that support the XMPP protocol, the company announced Tuesday.

When Google launched Google Talk in August of last year, the service was compatible with device applications that support XMPP (Extensible Messaging and Presence Protocol), including Cerulean Studios' Trillian.

At the time, Google also indicated its intention, now fulfilled, to make Google Talk interoperable with XMPP networks at the server-to-server level. It planned to do so in order to help foster what it calls a federation of XMPP networks, including ones from Internet service providers, vendors and private businesses.

Some of the networks that are now fully interoperable with Google Talk include EarthLink's Vling IM and voice service, as well as XMPP-based networks run by corporations, universities and individual users.

Google hopes its efforts will help "build a lot of momentum so the remaining major service providers of IM will follow as well," said Mike Jazayeri, Google Talk product manager, in an interview.

A major problem for users of IM services has been the lack of interoperability among the major providers: America Online, Yahoo and Microsoft. Those networks are based on proprietary protocols and users can't communicate across networks.

Last year, Yahoo and Microsoft announced plans to build links between Yahoo Messenger and MSN Messenger. Later, Google and AOL announced the intention to enable their respective IM networks to interoperate.

However, today's announcement isn't part of Google's collaboration with AOL, Jazayeri said.

"We believe this is an important first step toward a broader industry effort aimed at open communications among instant-message and voice providers," said Tom Hsieh, EarthLink's director of voice products and engineering, in a prepared statement.