While still wrestling with the exact approach, the IMS Forum plans to have a certification program in place by early next year that should help service providers feel more comfortable that IP Multimedia Subsystem gear will be interoperable.

That news comes as the IMS Forum this week released the results of its latest IMS Plugfest III event, which was held Oct. 15 - 19. Plugfest interop demos began about a year ago, making it the right time for the forum to move beyond mere demos and launch a formal certification program, said Michael Khalilian, chairman and president of the IMS Forum.

"We needed to get through one year of testing, and we accomplished that," Khalilian said, admitting that formally certifying IMS product interoperability remains a "controversial" topic. Exactly how the IMS Forum will certify products -- including whether the end result will be a true certification or a rubber stamp of approval -- will be decided by the IMS Forum in the coming months, he said.

"All IMS applications meet some level of the IMS standards," said Khalilian. “They were designed based on those standards.” But only a formal certification program can ensure that any deviations from the standards -- intentional or not -- won't hinder IMS interoperability.

For service providers, interoperability certification would surely provide an additional level of comfort. While IMS enables many new service capabilities, most carriers must justify the expense with cost savings. Without assurances of interoperability, those cost savings could be quickly eaten away by after-the-fact integration requirements.

The IMS Forum certification program will likely be announced around the time of IMS Plugfest IV, which will be held Feb. 25 - 29.

In addition to those efforts, the IMS Forum plans to publish additional recommendations and guidelines on IMS deployment, driven by its technical working groups, Khalilian said. It expects to release two new documents next week, focused on application infrastructure and security issues, respectively.

As for the latest Plugfest results, more than 16 companies participated in the testing, including sponsors Empirix, Intel and Sonus. Participating companies tested multivendor IMS interoperability for voice, multimedia, video-sharing, security and mobile services. Among the highlights: the first-ever multivendor interoperability demo of secure mobile 2G and 3G access to IMS services.

Other service tests included VoIP, instant messaging and fixed mobile convergence via femtocells; video sharing and multimedia; unified communications services; user and application profile handling; and security, reliability and robustness testing for IMS services.

"[The demo] focus was heavily on looking at applications and services important to service providers today, services that can help them generate revenues right now," Khalilian said.

"The major misconception about IMS today is that you have to be greenfield to transition to it," he said. "What we're telling the industry is that, even if you are upgrading your network today, these are elements that can continue to operate tomorrow within an IMS environment. You don't need to throw them away. This is an area service providers are very confused about. They are getting mixed messages from vendors."