IP Multimedia Subsystem (IMS) and Session Initiation Protocol (SIP) are said to have huge benefits for mobile phone systems. But these technologies may be accelerating the transformation of the wireline networking world, say experts.

For now, at least, experts say that IMS technology is much about wireline networks -- both the operators and the companies that make gear for them. It is the thing that will let you walk into work talking on your cell phone and be automatically switched over to the PBX once inside. It will allow you to IM with somebody on a moblie phone from your desktop PC. [Ed. note: Be still, my heart!]

In the end, these technologies may push carriers more rapidly toward IP networks.

“For the last six or seven years, carriers have had very little incentive to switch over to IP networks because customers don’t see any difference in the service after they do,” says Niel Ransom, outgoing Alcatel (NYSE: ALA; Paris: CGEP:PA) CTO. "An IP phone call sounds just like a circuit-switched phone call to the customer, so they will not pay any more for the service."

IMS, and the converged services it facilitates, might be the thing that finally brings about the change.

IMS is a common, IP-speaking medium in which service creators (wireline and wireless) can assemble, deliver, and bill for multimedia services built upon Internet applications, services, and protocols.

IMS carries signaling and bearer traffic over the IP layer and operates as a "routing engine" or "session control" application that matches user profiles with appropriate call/session-handling servers, then routes the call or session to the appropriate destination.

It allows the service creator to combine wireline and wireless applications in the same session, and allows sessions to be dynamically modified on the fly (e.g., adding a video component to an existing voice session). This makes possible "blended" services such as video telephony, chat, and multimedia conferencing.

The topic of some recent reports from Heavy Reading and Unstrung Insider, IMS was originally created for wireless services by the 3rd Generation Partnership Project (3GPP) standards consortium, but wireline service providers are now seeing that they can offer converged wireline and wireless services -- new, cool applications that customers are willing to pay more for -- based on the common language of SIP.

“Wireline organizations are all referencing it,” says Garland Sharratt of media server maker Convedia Corp. “They’re trying to align their core architecture with IMS, trying to tie in access into the IMS core. That core is at the heart of every new service deployed.”

Alcatel's Ransom agrees. So what's the result? He believes that one outcome will be that the carriers move more rapidly to VOIP.

“So what you’re seeing is IMS in the wireless world is driving VOIP acceptance in the fixed, wireline world, and operators are now changing out their class 5 switches,” Ransom says. “Everyone saw where they wanted to get to, but just had no immediate incentive to do so.”

When the devices on wireless networks begin communicating with those that live on fixed networks, that’s when things are going to get interesting.

For example: In a recent request for proposal (RFP) seen by Light Reading editors, U.S. carrier BellSouth Corp. (NYSE: BLS) says it is in the process of deploying a host of SIP and IP technologies. "BellSouth's target architecture would harmonize on the use of SIP for session initiation for all types of sessions -- IP telephony, multimedia, VOD, multicast video, etc.," the RFP states.

The IMS architecture is implemented in software that typically runs on a vendor's switch or commercial hardware platform, according to Unstrung Insideranalyst Gabriel Brown. Depending on the customer, the call/session control functions can be run either as dedicated hardware or as software loaded onto a next-generation mobile switching center or call server.

This common IP-speaking medium is driving fundamental changes in the way both wireline and wireless networks look. Ubiquity Software Corp.’s Jeff Liebl likens it to the conversion from mainframe/dumb terminal systems to the distributed processing of client/server systems. Instead of a monolithic central switch that does everything, the call control applications will be spread out to a number of software elements across the network. These elements include application servers (Ubiquity’s product), session controllers, media gateways, media servers, and home subscriber servers.

"The idea of a standardized session control architecture for SIP-based services is becoming central to both wireless and wireline networks," wrote Brown in his recent report titled “IMS: The Heart of Wireless & Wireline.”

Brown sees this driving forward the market for core IMS elements, such as the call session controllers and home subscriber server. It could easily be worth several hundreds of millions of dollars over the next few years, Brown says.

The cumulative effect of IMS on the industry will play out in the next five years. In a recent survey from Heavy Reading analyst Graham Finnie’s “Fixed-Mobile Convergence Reality Check” report, telecom professionals sketched out two of the most likely near-future scenarios. First, an environment may emerge where most voice calls are made over cellular networks using a cellular (or similar) handset, and the wireline network will be used mainly for broadband, entertainment, and data services.

The second possibility is a fixed-mobile convergence where customers own a multimode phone that is used to make calls over the most appropriate available network -- wireline or wireless. “In the core network, the boundaries between fixed and mobile technologies will be largely dissolved by 2010 to 2012,” predicts Brown.

Vendors have been formulating their IMS strategies for several years now, and some are beginning to bring product to market. Light Reading will review the IMS strategies and product offerings of the major telecom equipment makers in subsequent stories.

— Mark Sullivan, Reporter, Light Reading

For further education, visit the archived Light Reading Webinar:IMS: A Blueprint for Fixed-Mobile Convergence