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At the recently held Supercomm in Chicago, Pradeep Malhotra, MD, India operations, Continuous Computing, found out that people were talking a lot about IMS.

And this chatter did not start overnight. In December 2004, thirteen companies, signed a GSM Association MoU, to actively promote interoperability for SIP-based services. Following this, seven of them went ahead and conducted a test campaign in February 2005, and demonstrated cross-network and cross-platform interoperability. The trial used infrastructure based on IMS, and ran applications such as: voice instant messaging, video sharing, and gaming. Interestingly, using both 2G and 3G access networks.

What Is IMS
This is how various equipment vendors describe IMS (IP multimedia subsystem).

The Vitruvian Man: All parts in proportion and in symmetry with each other-inspiration for the IMS?

It is an international, recognized standard; it specifies interoperability and roaming; and it provides bearer control, charging, and security. What is more, it is well integrated with existing voice and data networks, while adopting many of the key characteristics of the IT domain. This makes IMS a key enabler for fixed-mobile convergence and value-based charging

At its core it is an IP multimedia and telephony network. It is defined by 3GPP and 3GPP2 standards and organizations, based on IETF Internet protocols. It is access independent as it supports IP to IP sessions over wireline IP, 802.11, 802.15, CDMA, and packet data along with GSM/EDGE/UMTS and other packet data applications.

It is a standardized reference architecture consisting of: session control, connection control, and an applications services framework along with subscriber and services data.

IMS was developed as an umbrella framework, for providing IP-based services, by the Third Generation Partnership Project (3GPP). It originally planned to develop specifications only for 3G GSM, however it has gone much beyond that now. To date, two phases, known as Release 5 and Release 6, have been published for IMS, which lay out the specifications for an IP/SIP-based network services architecture catering to both the span fixed and mobile broadband.

Why is IMS needed?
First, old equipment and technologies need to be replaced. If we consider that the last large-scale networking infrastructure deployments were in the tech-boom era in the 1990s-and their 20-year useful life is almost nearing an end-then within the next five years we should see a boom in the equipment and technology business again. Most of these replacements would be IP-enabled replacements. Even if all other factors remain the same, just the replacement market should create enough of feel good in the global market. Among others, the vendors are glued in to this hope and are feverishly pitching their new wares.

Then, the business scenario is changing. Pradeep Malhotra says, "If the telcos remain telcos, they will be wiped out of the market." IP has changed the telecommunications business. With the Internet hosting so many new services and applications for all types of communications, network operators are feeling threatened. While the others offer premium services over the telcos' networks, the telcos themselves are constantly being squeezed with bandwidth price cuts. A s study from Alcatel, titled IMS: Internet Age Telephony, says, "Many successful services are available today...some of the latest to be launched, are being proposed by Microsoft MSN, Yahoo, AOL, and Skype. Operators have devised the Internet Protocol Multimedia Subsystem (IMS), which is their architecture for Internet telephony and multimedia communications, to compete against these newcomers. Operators want to avoid becoming only low-margin bit-pipe providers."

Convergence: There is also the issue of convergence, which has been touted as the 'next big thing' for quite some time now. IMS can supports service convergence, by providing a common set of services across fixed and mobile networks; and it provides network convergence by providing cost savings that come with a single, core IP network. IMS is being looked at as the road to convergence because it enables technology-agnostic access to multimedia services.

How Is IMS Different?
Most of what IMS promises in terms of person-to-person communications is based on the 3GPP variant of SIP. So far, SIP has been the domain of the Internet, and services and applications based on it are a plenty on the Internet.

Though IMS can be called the telecom equivalent of the Internet, it differs from the Internet in one major way, says Krishan K Sabnani, senior vice president, networking research, Bell Labs. The Internet is a best-effort technology. A best-effort technology can promise anything, it cannot assure it. Besides, the Internet does not work very well when the network is overloaded. With IMS, Sabnani says, you can deliver what you promise.

Looking ahead, the aim of IMS is not only to provide new services but to provide all the services, current and future, that the Internet provides, says a more pedestrian Wikipedia encyclopedia.

Eshwar Pittanpalli, CTO, Lucent India elaborates, "IMS is not a technology. It is a way of giving the user the same experience irrespective of endpoints." Simply put, it provides the user a standardized interface for all the entities in the IMS architecture. It enables the user to access all the services seamlessly, independent of the access device. So if a Web surfer wants to hear Airtel's joke of the day (normally available to cellular subscribers only) he can go ahead and do it over a broadband connection. The service providers benefits too, as they does not have to create the service separately for their fixed broadband and or GSM subscribers.

Also, as opposed to the next-generation network approach, which aims at just carrying circuit services on top of the Internet protocol (IP), IMS offers operators the opportunity to build an open IP-based service infrastructure that will enable an easy deployment of new multimedia communication services-mixing telecom and data services, says an Alcatel white paper titled, Network Evolution towards IP Multimedia Subsystem.

And because IMS is based on open standards, the operator retains the freedom to create and provide the multimedia services with heterogeneous elements, without being bound to a particular equipment or technology vendor. Also, unlike in a traditional architecture, the network operator is not required to host all the services (and servers) at its premises. As long as the applications server are IMS (or SIP) compliant, services can be offered from anywhere in the network, without the need for physical presence of servers at the operator's premises.

So What Is Stopping It?
While services over the IMS are touted as next-generation, and technology is a major issue in their deployment, it is not the biggest. IMS is based the already-popular SIP. In fact, Pradeep Malhotra says that even 3G is not an absolute must for providing multimedia services (the raison d'etre for IMS). Users in East Asia take to the new services with gusto, while rest of the world does not. In the US, push-to-talk offered by Nextel is a big hit, but it has not caught on with the 3G subscribers in Europe. So the fuel for IMS is going to be culture or the mood of the people. The service provider has no need to invest in services the people are not demanding. But if there were a need, Malhotra says, IMS will greatly simplify the service-creation environment.

According to a report by Analysys Research titled, Delivering Strategic Benefits with IP Multimedia Subsystem (IMS), (published July this year) while vendors of IMS point to the immediate service opportunities to justify its short-term deployment, there seems to be no strong justification for immediate IMS deployment. Therefore, operators should not get distracted from their core revenue opportunities in voice and messaging and should not rush into decisions about implementing IMS. Though IMS promises services such as push-to-talk, mobile VoIP, video sharing, IP centrex, and instant voice messaging; these are as yet unproven, it says, and adds that in some cases, proprietary solutions may provide quicker, cheaper, or better-tested alternatives.

Some of the risks of IMS it enumerates-in short-term- are: uncertain demand, risk of revenue cannibalization, quality of service, interworking, and handset availability. Even if IMS is access and technology agnostic, its benefits can only be realized by high-end multimedia capable handsets. Analysys notes, "Operators should maintain their focus on the most attractive service opportunities, not just those enabled by IMS."

Even though the report may sound pessimistic about IMS, it is more upbeat on the prospects in the slightly longer term.

Who Stands To Gain From It?
Actually, everyone. The service providers today aim to have just one network to deliver all the needs of all the customers. The customers want newer services everyday, preferably delivered on a mobile terminal, and that too at a good price. And they will want to use these services the way they want, certainly not the way their service provider finds it convenient. And IMS can realize that future.

Alok Singh