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For years, IP multimedia subsystem networks have been forced upon wireless service providers who have been struggling to deploy them given they need to follow a rigorous and complex set of standards. The promise is IMS architectures will help service providers more easily deploy new broadband services such as voice over LTE, rich communications services and unified communications, helping them maximize revenue and strengthen subscriber loyalty. Likewise, cable and wireline service providers, who want to fulfill customer demand for competitive services like residential voice over IP, also have struggled deploying these networks, given they also need to follow the same set of mandated standards.
Bottom line, carriers of all types have not been enthusiastic about deploying IMS because of the associated costs, but they are forced to because it is mandated in the standards (3GPP, 3GPP2, TISPAN, PacketCable). In fact, IMS skeptics have always asked a simple question: why IMS? In an IP network, where devices and application servers communicate using SIP, they believe there really is no need for the complexity of IMS.
Thus, innovative wireless, cable and wireline carriers are beginning to challenge IMS. For the most part, large LTE carriers have committed to IMS thinking it was the only option, but frequently, the decision to implement IMS is forced from the top down without a clear business case to those who are managing the installation. And, with economic uncertainty continuing around the world, many LTE carriers are now realizing the benefits of IMS do not outweigh the exorbitant costs, so they are beginning to explore less expensive alternatives.
One alternative that shows early promise of being a credible alternative to IMS is SIP session management. As its name suggests, SIP session management provides a mechanism for managing SIP sessions. It also enables the management of new UC services consumers want, such as voice calls, instant messaging conversations, video chats and screen sharing – all from the same session. Furthermore, SIP session management enables the interaction among SIP clients, SIP-based applications and policy functions.
Managing SIP sessions is the nucleus of both IMS and SIP session management, and both use a control layer to manage SIP sessions, an application layer to support SIP-based applications, and an access layer to handle network and subscriber connectivity. However, SIP session management has fewer “bells and whistles” compared to IMS, eliminating many functions that are not directly related to managing SIP sessions such as breakout, charging, and media gateway functions. Eliminating these features makes SIP session management less expensive to deploy, configure and manage than IMS. SIP session management can reduce the capital expenditure costs by as much as 70%.
So, if SIP session management gives carriers many of the same benefits of IMS without the added complexity and cost, why have they not embraced it as the viable alternative? The current challenge facing SIP session management is it does not rely on a standard reference architecture like IMS. Thus, vendors who offer SIP session management solutions use different architectures, which may be proprietary or semi-proprietary in nature creating a “silo” environment in which customers are locked into a specific vendor for all – or most – of their communication services.
As a result, the market’s appetite for such solutions has been limited since proprietary solutions are not suitable for widespread deployments in heterogeneous networks. To overcome this roadblock, an open, non-proprietary approach to SIP session management is needed to support standard-based interfaces, provide an application creation environment in which third party developers can create new SIP-based apps, and interoperate with UC and IMS elements and apps.
Thus, to leverage their huge investments in IMS, carriers should consider using open, standards-based SIP session management in one of the following three ways: as an alternative to IMS, as a complementary solution to IMS, or as a transitory step in the evolution to IMS.
–As an alternative to full blown IMS, SIP session management is an attractive option. Using an IMS compatible interface, SIP session management solutions can invoke RCS and other IMS applications that would otherwise be too cost-prohibitive to offer. But, with an IMS-less RCS offering, where most of the SIP session management capability is transitioned to an RCS application server, SIP session management can provide a much needed life line to make RCS applications more mainstream. An open SIP session management solution can also provide the necessary charging and network management interfaces to easily add RCS offerings.
–As a complementary solution to IMS, SIP session management can help assimilate powerful UC capabilities with IMS and RCS applications. Users can invoke and combine UC and IMS/RCS applications, such as presence and video sharing with enterprise and external participants, as well as utilize some of the extensive capabilities supported by IMS (such as roaming). Also, LTE carriers can provide both hosted UC services to enterprises as well as traditional IMS and UC services to both consumers and enterprises, which is a win-win for them and opens multiple revenue streams.
–For those still aiming for a fully deployed IMS network, SIP session management is a pocket book friendly option to get started with basic IMS functionality. Once the SIP session management solution is deployed, additional IMS capabilities can be built on it.
As LTE carriers and service providers continue to invest in their networks and establish offerings that meet their customers’ personal and business needs, they should give serious consideration to complementing IMS with open, standard-based SIP session management or selecting it as the alternative solution to IMS. The savings in cost, time and hassle to deploy new services like RCS or UC applications without the complexity of full-blown IMS will translate into faster revenue stream and more satisfied customers earlier in the process.
