This week, we'll finish up the mini-series covering IP Multimedia Subsystem (IMS) progress with a re-cap on the issues and our analysis. We began the series with a hypothesis suggesting that "on paper," IMS is a great idea. But our bias before interviewing the experts who are working to advance IMS was that actual deployments are rolling along very slowly due to many factors, including the need for more multivendor interoperability testing of SIP (Sessions Initiation Protocol), the lack of IMS "hooks" for carrier operational support systems (OSS), and our belief that tension between wireless and wireline service network operations was a possible source of delays.

Countering our pre-disposition to the need for more proven multivendor SIP interoperability, Randy Waters at Comverse said that in Europe, his company has tested a wide range of SIP-based voice features within multivendor IMS core networks supporting residential VoIP, IP Centrex, and push-to-talk over cellular - along with messaging application testing (to a lesser extent) than the voice features.

Adding support to Water’s observations, Manish Mangal and Mike Logan of Sprint said that the carrier has worked with multiple vendors to solve some of the interoperability issues for SIP, and they have had “some good agreement on voice and voice extensions;” however “for other services like presence, video, and policies, the standard isn’t that mature and as these [other] services go, there is a lot of work to be done.”

So, testing our hypothesis about the need for more SIP interoperability, it seems that while voice features are pretty well supported, the industry still needs more work before IMS can support other multimedia services beyond voice.

Next time, we’ll look at our second and third hypotheses.

For readers who want to go back and look at the interviews we completed for this series, please click on the links here for views from:
* Ajay Gupta at Aricent
* Manish Mangal and Mike Logan at Sprint
* David Withington at Alcatel Lucent
* Randy Waters at Comverse
* Siroos Afshar at AT&T
* Bill Goodman at Verizon
Our thanks to these experts who helped clarify the issues and progress surrounding IMS.

Steve Taylor is president of Distributed Networking Associates and publisher/editor-in-chief of Webtorials. Larry Hettick is a principal analyst at Current Analysis.