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The Migration Path from Legacy Networks to IMS

By Dr. Ayal Itzkovitz and Tal Zoller            October 2006, Volume 1/Number 5

IMS Magazine

R ecently the need for legacy and IP-based services to interwork seamlessly across both fixed and mobile networks has been getting a lot of service providers’ attention. This realization occurred as it became evident that the move to the all-IP network of the future would not happen overnight. Though service providers are clearly interested in the promise of the IMS architecture; i.e., richer communications with new services and revenue streams, they cannot simply abandon the extensive legacy networks that currently serve their existing customer base. Doing so would neither be practical nor prudent. Conversely, the change to IP must be a migratory one that leverages the existing infrastructure, and the huge investment therein, yet moves the service provider rapidly towards the future network and IMS. Recently the need for legacy and IP-based services to interwork seamlessly across both fixed and mobile networks has been getting a lot of service providers’ attention. This realization occurred as it became evident that the move to the all-IP network of the future would not happen overnight. Though service providers are clearly interested in the promise of the IMS architecture; i.e., richer communications with new services and revenue streams, they cannot simply abandon the extensive legacy networks that currently serve their existing customer base. Doing so would neither be practical nor prudent. Conversely, the change to IP must be a migratory one that leverages the existing infrastructure, and the huge investment therein, yet moves the service provider rapidly towards the future network and IMS.

Many of today’s services will continue to exist, even in the new IP environment, but there will be more flexibility in how they will be used. Of course, the new environment will open up new service opportunities. But the reality is that, for quality assurance reasons, any large-scale rollout of these new services will likely be done gradually. Additionally, most service providers are unwilling for economic reasons to scrap a working network. So service providers are left searching for a solution allowing them to start migrating their network infrastructure and begin realizing some of advantages of the IMS architecture while preserving as much value in their current infrastructure as possible.

The Power of SCIM
A solution lies within the IMS architecture itself. SCIM (Service Capabilities Interaction Management) manages the interactions between and among the applications. A particularly important function of SCIM is to manage and control the interaction between applications and its features in disparate networks. This functionality enables service providers to deploy applications and features (such as IMS Application Servers, Presence servers or SIP Centrex) from their IP networks to mobile subscribers using 2G/2.5G/3G phones, or fixed POTS subscribers, all connected and running on existing circuit-based networks. It also allows the service provider to offer applications and features from their legacy networks to subscribers on their IP networks. This allows any combination of services to be offered to subscribers without regard for the network or device.

To date, the SCIM function has only been loosely defined by 3GPP. The reason for the lack of clarity correlates to the fact that there is a debate at the location of this functionality in regards to the network node in which it resides, especially in a pure IMS network. The SCIM function could serve as service interaction for pure IMS application servers only, or take a broader view of a service interaction core for a wide range of applications, platforms, and protocols. The SCIM function could be viewed as a coordinator in an all-IP network with the services residing on a network of application servers or as the coordinator in a hybridized legacy-IP network containing both legacy and IP service control points able to function in accordance with the spirit of IMS. The answer of course is both, with the latter being particularly important in the early stages of IMS adoption to large incumbent service providers with extensive legacy service infrastructure.

When viewing SCIM in this light it is easy to see how important this function actually is in forwarding the advancement of IMS. But it is also important to realize that SCIM, when deployed for the purpose of unifying legacy and IP service infrastructure across fixed, mobile or fixed-mobile networks, cannot be relegated to the edge of the network on an application server. In this case, SCIM must be implemented as a standalone core network element in order to interface with both SIP application servers and the interfaces of the legacy service infrastructure which varies widely from region to region and vendor to vendor. Deployment of SCIM at the network core enables unified services without any change to the service layer. By adopting the SCIM approach, service providers can actually begin the evolution of their networks to IMS, thereby building a strong foundation on which to add new IP services without the need to completely abandon their existing legacy service infrastructure or their existing deployed legacy subscriber base.

Advancing towards IMS
While 3GPP and the other standardization organizations have been focusing on defining how a pure IMS network would look, function and behave, the operators’ reality dictates a different point of view. A good example of this: Verizon (News - Alert) Wireless recently announced efforts looking at the right migration towards IMS, with a particular focus on the interaction between the IMS network buildup and other domains available or becoming available in the network — such as SOA, web services, existing IN platforms or IPTV (News - Alert) . This is the first public example of a Tier 1 operator taking the helm towards the goal of easing the transition from current networks to the all-IP networks of the future, and having a committed group of network equipment providers behind it (in this case Cisco, Lucent, Motorola (News - Alert), Nortel and Qualcomm).


Real World SCIM Deployments
There are already several examples of core network SCIM deployments today. A North American mobile (CDMA) service provider is using SCIM to enable its approximately 3 million subscribers to make and receive calls with a single number on virtually any phone: wireless, wireline or VoIP softphone. In addition to CDMA, the service provider can offer SIP/IP based services to new markets including fixed line, enterprise, and advanced multimedia communications. SCIM functionality enables the convergence of SIP clients to the CDMA network without compromising the full connectivity to its existing Wireless Intelligent Network Service Control Points (SCPs) including Prepaid SCP and an additional SCP running advanced, location-based VPN services.

In another recent deployment, an Israeli mobile service provider chose a next-generation switching solution that provided a clear migration path to IP-based services but also interacted with its existing IN-based services. It deployed SCIM functionality with a softswitch and SIP-based application server to create an IMS architecture ready f ...an Israeli mobile service provider chose a next-generation switching
solution that provided a clear migration path to
IP-based services but also interacted with its existing IN-based services.
or the IP protocols of today and tomorrow. The service provider can now deliver IP-based services to its mobile 2G, 2.5G and 3G subscribers. It can expand to new domains by using its IP network to deliver services to new devices, providing IP access, VoIP connectivity, as well as the standard telephony services that were already deployed in its network.

The Next Steps
Consumers and businesses are looking for convergence across all of their communications; this is a comprehensive spanning requirement that goes way beyond the search for cheaper calls. While service providers are already looking at moving to an IP-based network, they must also meet these demands of their customers today or loose their market share. We see these trends invoking a new perception across service providers globally, and spanning from Tier-1 (like the Verizon Wireless A-IMS example) to developing markets and smaller providers — the need for evolutional migration to IP and IMS. Service providers have begun to bridge the transition and address this need by implementing SCIM functionality. As more service providers become aware of SCIM, it becomes a new foundation for implementations across their existing network. We are seeing service providers using the SCIM layer as the transitional key towards opening more and more IMS- and IP-based doors, while continuing to leverage their invested network toward their mass subscriber base.

Dr. Ayal Itzkovitz is CEO of Convergin and Tal Zoller is Vice President of Business Development of Convergin. For more information, please visit the company online at www.convergin.com.

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