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Eye On IMS

What is IMS, Really?

By Grant F. Lenahan


IMS (along with its permutations — NGN, MMD, and PacketCable Multimedia) is approaching that stage where it is becoming the ubiquitous topic of our industry, yet it’s also “amorphous” — many still aren’t sure exactly what it is, or should be, while others have widely diverging opinions. This is the dangerous stage at which IMS could easily move on to be a “hype bubble” — or it could be the long-term roadmap for our industry’s business and technical future. Some choice! Mobile operators see IMS as a path to 3G services, although few have yet emerged. Broadband operators see IMS as a path to VoIP and Fixed-Mobile Convergence (just look at who’s driving the 3GPP’s Voice Call Continuity standards — it’s not the GSM community). Stalwart switch vendors see it as the enabler for softswitches and VoIP, (define - news - alerts) while IT and data vendors see it as the enabler of Service Delivery Platforms (SDPs).

It seems to me that they are all correct to a degree, but none of these views capture the essence of what IMS is, and certainly not what it needs to be for our industry to prosper over the next few decades.

So what is IMS? One thing is for certain: IMS is not just about the movement from circuit-switched voice to SIP-based VoIP, although it surely will, and must, accomplish that. It also must be more than a technology to provide convergence in its many forms; although it’s also great for that too. And it cannot be only a path to multimedia and IP service, although that is, in many ways, getting closer.

Let’s begin with the essence of IMS, and do that by dissecting its name: the IP Multimedia Subsystem. That name says a lot:

First, it is intended for networks using the Internet Protocol (IP). The IP network of today — the Internet — is clearly “business model challenged,” and traditional fixed and mobile vendors are struggling to make an economic model work for them.

Next, it is Multimedia, allowing the delivery of voice, messaging, video, and other data services both concurrently and “blended together.” This is pretty special, since, in theory, it would break down both technological and service-specific “silos” or “stovepipes” that have long hampered service innovation and driven up systems integration costs.

Finally, it is a Subsystem. Say what? Well, the real point is that IMS is not a network per se, but a set of network-enhancing resources.

Let’s back up to the root problem, which is also the industry’s root opportunity: IP. IP is wonderfully flexible and interoperable. In fact, it’s so flexible and interoperable that service innovation has moved out from the core to endpoints — PC clients, third-party service providers (think: Vonage (news - alerts), Google (quote - news - alerts), Skype (news - alerts), Yahoo (quote - news - alerts)). This decentralized innovation has resulted in a cornucopia of new services, but has also resulted in problems for both operators (who feel dis-intermediated, and thus are struggling for a business model) and for end-users (who must deal with poor security, non-interoperable services, multiple passwords, chaotic billing, and inconsistent QoS, among many other problems).

It’s also clear that aside from a very few notable stars, no one has figured out how to make money using the traditional Internet model.

IMS aims to fix that. It offers some very basic tools to move the Internet to its next level, and to enable operators to profit from IP networks. IMS (along with the OMA, ETSI, and Cable Labs) defines:

A SIP-based session model so that associations, “calls,” and other services can be identified and controlled. It is interesting to note that a similar model can be applied to non-SIP services as such, greatly extending IMS’ reach and usefulness.

Along with work in the OMA, a set of shared, re-usable “enablers” that should speed service development, allow operators to offer value-adds to third parties that want them, and enhance a consumer’s overall on-line experiences.

A charging (billing) infrastructure with the ability to recognize sessions of many kinds, and to operate in real-time to support a wide range of commercial models, including those collaborative with innovative third parties.

A set of mappings (in progress) to support a range of networks, including DSL, Cable/HSD, 3G, FTTx, broadband wireless WANs and LANs, as well as interoperability with cellular and fixed voice and IN networks.

So there you have it. IMS supports IP networks. It supports service innovation. It supports flexible charging. It supports core network intelligence. And it supports these — in theory — across a wide range of broadband and legacy networks. And therein lies the real magic of IMS. It’s not associated with one vendor, one technology, one service. It’s the “lingua franca” that lets service innovation take place, yet enables operators and other service providers to offer value-adds that augment a consumer’s and enterprise’s experience by adding simplicity, security, and personalization.

Or, as I see it, it leaves the genius of IP networks mostly alone, while patching the holes that stymied attempts to offer common, easy-to-use, secure services.

Grant Lenahan is vice president and strategist, IMS Service Delivery Solutions at Telcordia Technologies, Inc. For more information, visit (news - alerts)

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