The latest buzzword in telecommunications isn't the name of a box, an application or a service. Instead, IMS is a way of organizing all those elements and more.
Internet Protocol Multimedia Subsystem is an architecture that defines how IP networks should handle voice calls and data sessions. It essentially takes the place of the control infrastructure in the traditional circuit-switched telephone network, with the key difference that it separates services from the underlying networks that carry them. That way, services such as text messaging, voice mail and file sharing can reside on application servers anywhere and be delivered by multiple wired and wireless service providers.
Information about the preferences and access rights of each user could be held in one system and made available on many others for roaming.
"The subscriber is at the center of the universe now, instead of everything revolving around the network," says Joe McGarvey, an analyst at Current Analysis. Whether users are in the office, at home or on the road, they will have access to the best possible resources and ways of communicating, according to McGarvey and other industry analysts, carriers and vendors. Plus, IMS should make it less expensive and risky for service providers to invest in new services, a boon to companies, he says.
"They're going to see a lot more interesting applications [that will be] introduced a lot more quickly than they are now," McGarvey says.
IMS originated in the Third-generation Partnership Project (3GPP), which was looking for a common way for 3G mobile operators migrating from Global System for Mobile Communications to deliver data services. However, in the past year or so it has been embraced by a number of other standards bodies for both wired and wireless networks. At its core is Session Initiation Protocol (SIP), a signaling system for setting up and handling calls and data sessions, which already is the standard for VoIP products. That is helping IMS gain backing from infrastructure makers, service providers and software vendors.
But the wide availability of SIP also could be the downfall of IMS, according to David Passmore, an analyst at Burton Group. Using enterprise communications gear or peer-to-peer software that uses SIP, both corporations and consumers could choose to handle their own voice or data sessions and get most of the capabilities of IMS. That would leave carriers in the role of selling pure high-speed IP connections, Passmore says.
"Long term, I'm not convinced that IMS is going to be successful," Passmore says. "Ultimately, fat pipes may win out."
The complexity of IMS makes its road to deployment even steeper, he says, though the architecture can be boiled down to three basic parts. They are the Home Subscriber Server, which stores information about each user; application servers, which run the services that subscribers use; and the call session control function, which regulates how each session works and is merged with other sessions. SIP is the glue that holds all those elements together. The traditional circuit-switched telephone network can tie into IMS via gateways.
Having all services handled on one architecture could have several benefits to companies, according to analysts and others. One of the first windfalls is likely to be fixed-mobile convergence, providing an infrastructure for combination Wi-Fi/cell phones, Passmore says. IMS also would help to extend push-to-talk functions to more cellular networks.
In addition, more users could participate in a given application, such as videoconferencing, if it could be delivered to mobile devices as well as office PCs. Interoperability among service providers using IMS could bring in participants from parts of the company that use different carriers. And users could start multiple communications applications, such as text messaging, voice, file sharing and videoconferencing, from one software portal on a device, says Kevin Mitchell, an analyst of Infonetics Research.
That capability can already be set up in an enterprise or service provider network with Nortel's Multimedia Communications Server (MCS) products, according to Mike Doerk, senior manager of wireline marketing at Nortel. MCS will play the role of application server in a 3GPP-compliant Nortel IMS lineup coming in the fourth quarter, he says. Reaching beyond the 3GPP standard to bring IMS to all types of networks will take more work, but Doerk believes individual vendors will be able to build such systems within a year. Interoperability among different vendors' IMS platforms is perhaps a year or two away, he adds.
Nortel rival Cisco is committed to IMS in the long term but believes there are still issues to be worked out. The architecture as defined today isn't secure or scalable enough, says Art Feather, manager of architectures and standards for Cisco's mobile and wireless organization.
However, carriers are already working on IMS. Burton Group's Passmore says many contracts with vendors have been signed and initial deployments should come in 18 to 24 months, beginning in Europe.
SBC won't say when it will roll out IMS but is "deep in the throes of testing," says John Erickson, a vice president at SBC Labs. The architecture is intended mostly for voice services and will allow SBC to expand its VoIP offerings, but it could be used for data services too, he says. One issue that still needs more work in standards bodies is how the IMS infrastructures of different carriers would interoperate, Erickson adds.