Dozens of vendors are marketing equipment based on the standard, and so many carriers have expressed their plans for deployment that it is easy to forget that the IP multimedia subsystem is still not much more than a concept. The integrated services and more efficient application development that IMS will allow give the industry sufficient hope that this complex collection of standards will pay off in the form of a new, revenue-generating network and service architecture.

But before IMS gets that far, there's still a lot of work to do. That work comes not only in the form of ongoing product development, but also in the form of the internal and external tests and interoperability events being conducted by various companies and groups this year and well into next year.

All through their own IMS product development processes, vendors have been conducting their own lab tests and trials and gathering information to share with the rest of the industry, said Mike Cooper, director of global strategy and marketing for Lucent Technologies' Converged Core Solutions group. “During our entire development cycle, we are constantly feeding information back to our standards people, who are bringing it to the Multi-Service Forum, 3GPP, ETSI [European Telecommunications Standards Institute], TISPAN [ETSI's Telecoms & Internet Converged Services & Protocols for Advanced Networks group] and others,” he said.

For a lucky handful of vendors, those internal tests already have transitioned seamlessly — we are talking about IMS, after all — into pre-contract tests in the labs of network operators, and in a few cases, into well-publicized, albeit tightly controlled field trials. However, while demonstrating the capabilities of IMS in a lab or another controlled environment brings the industry a step closer to realizing the benefits of IMS, they don't perfectly emulate how an IMS architecture will perform in the real world, amid the complexities of large multi-vendor, inter-connected networks spanning the globe. Research firms such as Infonetics and Yankee Group also have pointed out that there are practical gaps in the IMS standards that need to be addressed. That's where interoperability events, plugfests and certification testing programs run by industry trade groups come in.

The most notable recent interoperability event was the MSF's Global Multi-Service Interoperability (GMI 2006) test. The MSF has held GMI events in each of the last three years, attracting a growing number of vendors and carriers from different countries. This year, almost 30 vendors brought IMS-compliant gear to five lab locations worldwide, including four labs run by carriers that have committed to deploy IMS. Observers agreed the GMI 2006 brought a level of scale and industry interaction that wouldn't be possible in a single-lab environment.

Speaking in particular about the GMI 2006 event, Joe McGarvey, principal analyst for Current Analysis, stated in an e-mail interview, “The major value of the GMI 2006 event for equipment vendors is that it provides them with what amounts to a sandbox to play in for a couple of weeks, mixing and matching their products with equipment from vendors offering complementary products. Participating vendors tell me that they just can't reproduce the interop situations in a lab environment that they can achieve in a test event such as GMI.”

“The advantage of working with the MSF and creating a lab of multiple implementations and multiple vendors is that having a lab of this scale is significant because nobody else has the ability to gather all of this in one place,” said Mehdi Ghasem, chief technology officer of Lucent's Converged Core Solutions group.

Moreover, McGarvey said an event like GMI 2006 helps the industry confront implementation issues that probably were not addressed by the standards groups that developed IMS. “Standards exists essentially in the theoretical realm, while the GMI event is real-world and deals with implementation. The event is also a great place for vendors to ‘audition’ for the carriers involved.” As evidence of the value of that audition, McGarvey said several vendors that participated in the GMI 2004 event ended up being on BT's short list of suppliers when the U.K. carrier later announced its 21st Century next-generation network buildout last year.

“For the industry itself, it's a proof point,” said Lucent's Cooper. “You can see how things get put together, and see how it all works in a multi-vendor environment. You also make contacts that hopefully turn into deployments.”

Tom Phelan, principal architect for Sonus Networks, added, “It was the first time some of our equipment was getting out of our labs. Carriers are interested in seeing the results because it gives them a better feeling that they can pick and choose their network parts because they have seen them work together.”