Completely overhauling the global telecom network per complex yet open-to-interpretation specifications can't be easy, right? Then why the surprise when the evolution to IP multimedia subsystem has been slow slogging — especially when service providers have so many near-term challenges facing them, from new competitors to new opportunities and more?

That's probably the fairest evaluation of industry progress toward IMS — but as always, the more interesting truth is in the details.

Many efforts remain behind the scenes, but conversations with vendors about active requests for proposals and trials reveal that IMS activity is out there. Session border control vendor Acme Packet is involved with more than 100 IMS projects around the globe, said Seamus Hourihan, vice president of marketing and product management for Acme Packet. Alcatel-Lucent also has seen increasing interest: “not huge, but a number of customers are making significant IMS decisions,” said David Withington, director of marketing for Alcatel-Lucent's application division.

The need to add other functionality to IPTV is likely to drive providers to adopt IMS in a major way, said Steven Hawley, senior IPTV analyst with MRG and author of a new report, “IPTV, IMS and the Emergence of Multi-Service Convergence,” but they won't want to commit to large IMS platform investments when standards are still in flux.

“It's possible today for IPTV middleware to be extended through a services delivery platform and Web services 2.0,” Hawley said. “Companies like Integra5 are doing that for caller ID on the TV.”

But as service providers want to differentiate their IPTV services, it can become an operational nightmare to do the required integration on a per-service basis. “You are going to want to put all the data required to do that into a common repository, where every service can access it,” Hawley said. He expects to see service providers pulling pieces of IMS into their networks but making the major commitment in two years or more, when standards work is done.

In the U.S., AT&T is leveraging IMS in the voice-over-IP portion of its U-verse network. Today, IMS elements are used to deliver standard features such as caller ID and messaging, although IMS-driven voice and video integration is in the offing. Verizon, meanwhile, has wrapped up a very long evaluation of IMS gear and is moving into commercial deployment beginning early next year, said Bill Goodman, director of corporate technology for Verizon. The carrier's IMS moves have been watched closely, and its cautious pace has contributed to concerns about the future of IMS.