IP Multimedia Subsystem (IMS) has been widely accepted as the unifying network architecture of the communications industry but still has “gaping holes and inadequacies” which must be addressed before it is widely adopted, a Yankee Group report concludes.

“IMS Architecture: Time for Introspection and Reality Check” says carriers want IMS for its ability to facilitate fixed-mobile convergence and rapid new service creation and delivery but must proceed cautiously because the vendor solutions available today are not fully standards-compliant and the standards themselves aren’t mature to the point they allow vendor interoperability.

“That is what most carriers are doing today, anyway” said Ari Banerjee, Yankee Group senior analyst. More aggressive deployment is virtually impossible because the lack of “plug and play” capabilities requires major integration work any time a carrier deploys IMS equipment from more than one vendor, he said.

The role of IMS in enabling fixed-mobile convergence and service brokering, where network elements are reused to deliver multiple services, is also blunted, Banerjee said, by immature standards and the lack of support for both Session Initiation Protocol-based services and non-SIP services.

“If you look at service brokering, which is one of the things that IMS is supposed to enable, many of the services today – IPTV and many kinds of VoIP – are not SIP-based and cannot be supported,” he said. “IMS is all focused around SIP and there needs to be support for non-SIP based services as well.”

Many service providers are taking a Service Oriented Architecture (SOA) approach to maintain their legacy assets in the transition to an all-IP world, Banerjee said. IMS development needs to take that trend into account.

“That needs to be a part of your overall service delivery layer – SOA has to be part of whole offering,” he said. Otherwise, service providers risk simply creating another silo of service offerings that are IMS-based but aren’t integrated into legacy offerings.

Banerjee believes service providers need to come together under one umbrella to drive standards forward. Individual efforts, such as Verizon’s Advanced IMS drive with its vendors, won’t have the same impact, he said.

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