June 2000

BY JIM MACHI

In my view, a softswitch needs to have at least three characteristics, though a more rigid definition will undoubtedly include others:

• Integrates the Internet telephony and circuit-switched worlds.
• Duplicates Class 4 and 5 switch capabilities.
• Operates in the classic public network environment, where call control is separate from media flow.

CALL CONTROL
This last characteristic is particularly important because it makes the softswitch more suited to an MGCP or Megaco call control model, where the call control environments are architected in a distributed fashion. This decomposition of the call and media control flow, as compared to H.323, is architecturally more consistent with the public network view of a Public Switched Telephone Network (PSTN) call using SS7. However, in an H.323 environment, I would still consider a gatekeeper to be a type of softswitch, since the gatekeeper -- at a minimum -- routes calls and translates the digits collected to an IP address. A gatekeeper can also perform network management functions, but in my definition, an H.323 gatekeeper would essentially be a subset of a softswitch.

A distributed call control, or MGCP-type environment includes:

• A signaling gateway to handle the call control.
• A media gateway to handle the mediastream such as fax, conferencing, and voice.
• A media gateway controller to direct the mediastream.

Typically, there's not a 1:1 ratio of all three of these systems. Multiple media gateways can be controlled by a single signaling gateway and a single media gateway controller. The media gateway controller is the "brains" of the operation, since it decides how the call flow is routed. In this scenario, I consider the media gateway controller to be the softswitch, since it routes the call and integrates the IP telephony and circuit-switched worlds by being able to translate from disparate call control environments (potentially SS7 to H.323, H.323 to MGCP, Megaco to SIP, SS7 to MGCP, etc.) using sophisticated call control stack translators.

It's also important to note that all these call control environments have open APIs, which is another important characteristic of a true softswitch. Open APIs allow applications to communicate with the softswitch -- delivering application integration and flexibility that are to me the most important characteristics of today's softswitch.

APPLICATIONS
What kind of applications are we talking about? Potentially a multitude of applications as they exist in enhanced service systems in the PSTN world. In these systems, the enhanced service systems are adjuncts to the network, handling applications like network conferencing, network IVR, fax serving, or network voice mail. Also, because the applications interoperate with a softswitch, the softswitch can handle telecom-hosted applications. The softswitch can be the brains that let an ISP or corporation outsource an application.

Consider the announcement in March of NetCentrex, who creates IP Centrex services and sells them to carriers and service providers. By working with NetCentrex, ISP Pagoo now has the ability to add Voice-over-IP (VoIP) value-added services. It's done by placing a call, saving a voice mail, or forwarding a call to, for example, a cellular phone -- all by using telecom hosting via NetCentrex services. Also, softswitch provider Vsys has announced a "porting center" where a company can develop code via a hosted application environment. This would benefit the developer tremendously by enabling testing against live networks without having to build up their own network in-house.

As the softswitch continues to evolve, the ability to incorporate features like directory services will become ever more important. Imagine in a large network being able to dial a call by looking up a name in a database using a directory service instead of having to depend on an operator to do it for you. If you could access the directory and dial the number using spoken commands, it would be even more convenient. And these are only simple examples.

CHECK IT OUT
Since the softswitch is built on open systems, making it flexible, we will continue to see it used in more interesting ways. Every time I go to a CTI or IP telephony tradeshow, I see the softswitch become more prominent. You can check it out for yourself at INTERNET TELEPHONY� EXPO in San Diego, October 4-6. Be on the lookout for softswitches -- and the applications they enable.

Jim Machi is director, product management, CT Server and IPT Products, for Dialogic Corporation (an Intel company). Dialogic is a leading manufacturer of high-performance, standards-based computer telephony components. Dialogic products are used in fax, data, voice recognition, speech synthesis, and call center management CT applications. For more information, visit the Dialogic Web site at www.dialogic.com.