These days, softswitch is a term that's often used -- maybe even overused.
It's the new Internet telephony buzzword. It seems like any piece of
software that does some kind of switching is being called a softswitch.
That's an awfully broad definition.
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.
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,
- 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.
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
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.