The convergence of wireline, cable and mobile networks is getting closer to reality. And the technology that’s expected to make it all happen – known as IP Multimedia Subsystem (IMS) – is maturing quickly.

That’s the finding of a recent interoperability test of IMS platforms that was sponsored by the IMS Forum, an industry association consisting of 50 equipment vendors and service providers.

Ten companies that sell IMS hardware, software and test equipment to service providers participated in the IMS Plugfest, which was conducted in January at the University of New Hampshire’s Interoperability Lab (UNH IOL).

The IMS Plugfest represented the first-ever test of IMS interoperability across products from multiple vendors. The IMS Forum will sponsor a second IMS Plugfest in May or June.

"What we were able to create was a true multivendor IMS network and demonstrate that we can support applications and services based on the interoperability of the transport layer," says Manual Vexler, who sits on the board of directors of the IMS Forum.

The test included 15 carrier-grade platforms valued at $15 million. Using dual-mode mobile phones and a number of VoIP and Wi-Fi user equipment simulators, the test was able to demonstrate voice services including fixed-mobile services, IP Centrex and PSTN gateway.

"This is the fist time that this many vendors have been able to come together and hash out what happens when you have a proxy from vendor A communicate with a server from B," says Lincoln Lavoi, senior engineer at UNH IOL.

The IMS test bed was up and running for six days, with around 30 network engineers working 50-plus hours to test their equipment.

Participants were able to place calls through the network for IP Centrex applications. They also were able to place an interdomain IMS call and emulate SS7 gateways.

"We have a very good level of confidence in IMS," Vexler says. The Plugfest showed that "interoperability among the vendors is a reality. We’ve seen it. It was easy to put together."

Chad Hart, product marketing manager for test equipment vendor Empirix, says the Plugfest results were good news for service providers because the IMS standards being tested are new, ranging from three to 18 months old.

"We were pleasantly surprised at how smoothly it went," Hart says. "There is still lots of work that needs to be done, but that will get done with future Plugfests. A lot of progress has taken place in a short period of time."