The opening of telecommunications markets through deregulation, in concert with innovative technology, is creating both challenges and opportunities for developers, service providers, and users of the network infrastructure and services. The availability of attractive new functionality is fueling market demand for connectivity, services, and resources. The challenges in this environment for service providers, exchange carriers, and other infrastructure players are the following:

• how to create and deploy new, differentiating services quickly and economically
• how to ensure that the telecommunications infrastructure remains open to change, accessible to growth, and easy to manage
• how to safeguard and leverage their investments in applications and equipment

A new generation of cost-effective, flexible switching technology is making the implementation of new services technically feasible and economically compelling. Through openness, the network infrastructure can accommodate and integrate a variety of external resources seamlessly and can adapt to tomorrow's technologies. Through scalability, networks can be configured to meet initial market demand and yet expand in both size and scope as the market grows. Through high performance, the telecommunications environment can sustain dynamic loads in real-time even as subscriber populations expand. Finally, through programmability, a wide range of current and future requirements can be fulfilled flexibly and economically.

First, through programmable switching, a logically distinct, visible model is established for call control and processing—that is, the core-switching function. Although the practice of modeling call flows in an identifiable manner initially grew from the need to computerize the function in order to achieve high call rates, programmable switching provides an architecture to support that model. This approach contrasts with previous-generation technology such as private branch exchanges (PBXs) or central office (CO) switches that embedded switching and applications in a single fixed system. The call-control model may be centralized and monolithic or distributed and modular by varying degrees. With this approach, the model may be focused narrowly on traditional switching functionality, or it may extend to, for example, new services such as fax, video conferencing, voice processing, one-number, or prepaid services.

An increasingly used method of implementing the architecture of programmable switching is based on the open and distributed client/server computing model. Like the computer industry before it, the telecommunications industry today is discovering the benefits of moving from large, proprietary solutions to open, scalable platforms and the importance of standards and interoperability between hardware platforms and software applications. Furthermore, the network infrastructure itself is making possible the concept of efficient clients and servers, whose system resources can be geographically distributed where and when they are needed.

Figure 1 illustrates the parallels that exist between the computer and telecommunications industries:

Figure 1. Switch-Market Evolution

Second, programmable switching opens the call control/processing model so that developers can implement new and unique services. This capability enables service providers to differentiate their offerings in a highly competitive market. How open and accessible that programmability is varies greatly. In many cases, functions are implemented by the switch supplier, using proprietary software that is relatively inaccessible to others. In contrast, some switches can extend programmability to developers and service providers by allowing them access to the switch-software environment on one or more levels. Using open strategies such as application programming interfaces (APIs), industry-standard interconnection devices, and high-level host-resident development tools, programmable switches can be tailored to implement unique services that meet individual market needs. As a result, carriers and network operators using an open switching platform can develop services much more rapidly and flexibly and deploy them at a lower cost.