The precise definition of a Softswitch is somewhat controversial due to its numerous service offerings and implementation options. Here is one general definition:

The Softswitch is a collection of products, protocols, and applications that enable any device to access telecommunication and/or Internet services over an IP network.

Looking a little closer, the term Softswitch refers to set of technologies which perform the functions of a switch, by establishing connections for end-to-end communication. A Softswitch can co-exist with a traditional circuit switch, and provide similar services using packet switching technology. The services that can be supported include voice, fax, video, data, and new services that will be offered in the future. The end devices include standard telephones, IP telephones, computers, PDAs,beepers, pagers, video conferencing terminals, and more. Softswitch technologies may extend beyond IP networks to other forms of wired, wireless, and broadband networks.

The Softswitch is perhaps the most significant technology that is driving a shift from traditional circuit switch based telephony to IP packet based networking. Softswitch uses software to make connections between devices, and handles voice, data, and routes calls across different types of networks.

FIGURE 1 Example of Softswitch in a Network

Softswitch technology enables connectivity between the Internet, wireless networks, cable networks and the traditional telephone networks. FIGURE 1-1 illustrates the network convergence that can be achieved using Softswitch. Softswitch enables the Telephone network to communicate with the internet world, and vice versa. The scheme of connectivity, directory numbering system and billing mechanism of the telephony world is made available to other networks (including the internet) using Softswitch.

The traditional telephone network uses Class 5 and Class 4 circuit switches along with Time Division Multiplexing (TDM) technology to transport voice data. It also uses the SS7 signaling network to handle call setup and teardown, plus other functions. The traditional telephone network is integrated with the IP network by using certain Softswitch components, including Media Gateways (which move voice data between dissimilar networks) and Signaling Gateways (which move call signalling data between dissimilar networks).

Most Softswitch deployments support Class 4 (toll center) switches, Class 5 (Central Office) switches,and related value added services. With the evolution of the Internet economy and e-commerce,the service offerings from network operators, Internet Service Providers (ISP), Network Service Providers (NSP) and Application Service Providers (ASP) are merging. The ability to integrate communication and services across diverse networks makes the Softswitch attractive for these businesses and applications.

The International Softswitch Consortium (ISC) is a body represented by various technology leaders, telecommunication equipment manufacturers, ITU and IETF. ISC views Softswitch as a collection of technologies (not a specific product) that enable next generation  telecommunication services based on open standards.