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Special Focus
March 2001


The Many Faces Of A Softswitch


[Go right to In Search Of Softswitch?]

The term "softswitch" has evolved over the last 18 months, and is now very loosely applied to many different products with very different capabilities. A recent count from the analysts at RHK revealed over 180 products all claiming to be a softswitch. While the term can be defined only in very general terms, it is more important to focus on the types of softswitches that have emerged.

Very broadly, a softswitch provides call routing/call state functions and controls connectivity within IP networks and between IP and the public switched telephone network (PSTN). Note that softswitches are different from media gateways, which in essence provide a physical hardware bridge between the PSTN and IP networks. Media gateways (also known as media gateway controllers), require a softswitch to provide additional intelligence and direct the call routing functions. Some manufacturers have hybridized the two types of products, adding some softswitch capabilities to their media gateways.

From these very broad definitions, softswitches are much better understood if looked at from the perspective of the business problems they solve. The distinction of whether a softswitch is hardware or software, or both, is not important; rather, the importance lies in a softswitch's core competence.

Operating at the network level, and providing connectivity between the PSTN and an IP network, are softswitches that are often embedded in the hardware media gateways. These systems provide Class 4 types of network functions, i.e., moving calls between two networks, and typically have the robust port densities that service providers require. These initial softswitches focus on the rapid offload of data (modem) calls from the PSTN to the Internet and cost-effectively free up TDM circuits for their intended purpose, i.e., voice traffic.

They are also used for packet-based "tandem routing" functions so that calls can traverse the PSTN effectively. The goal of this softswitch is fairly simple -- to provide call control, call routing, and interconnection at the core of the network and interface with the SS7 network. When compared to a traditional tandem switch, they offer significantly lower capital and operational costs. These Offload/Tandem routing softswitches provide a cost reduction strategy to help service providers transition their circuit-switched networks to a packet-based infrastructure that allows for cheaper transport.

Another type of Class 4 functionality, also at the core, offers capabilities like "call completion" services such as pre-paid calling cards and automatic dialing of 411 information calls. These used to be called service nodes in the old AIN framework and were typically devoted to specialized applications. These services can be delivered more cost effectively over a packet-based network, but more importantly deploying this type of softswitch begins to represent new revenue opportunities for service providers. Call Completion Services softswitches are relatively new, but they will become prevalent as IP-based voice services gain recognition.

In the last year softswitch technology has accelerated rapidly beyond the narrow functionality of Class 4 softswitches, to newer softswitches with features normally attributed to Class 5 switches directly controlling IP endpoints. There are three significant categories of Class 5 softswitches on the market today. In general these softswitches are responsible for initiating call set up and tear down at the edge of the network, but like Class 4 switches, they tend to focus in on certain business problems to be solved. The three categories offering basic Class 5 replacement services are POTS/Residential softswitches, End Office/IP Centrex softswitches, and the Applications-Enabled softswitches. Each category of Class 5 softswitch provides a feature set designed to serve different kinds of applications.

The "POTS/Residential" softswitch offers the basic features residential customers expect such as call forwarding and call waiting. They tend to replicate current residential switch capabilities (in a software-based environment) so that the capabilities become much more cost-effective for a service provider to manage. POTS "residential" softswitches will serve the needs of many service providers who want to offer call forwarding, call waiting, caller ID, and other popular consumer packages.

End Office/IP Centrex
The next level of Class 5 softswitch is focused on what is typically referred to as End Office/IP Centrex capabilities. These softswitches offer more business-oriented functionality, such as call conferencing, call hold, call park/pickup, hunt group routing, etc. In addition to replicating commonly used office features, these softswitches have added some Web-based provisioning, which will make these traditionally complex services much easier to manage for the service provider. The end-office applications on these softswitches enable a small or medium-sized business (SMB) to replace current Centrex offerings with the same familiar functions, add a few more capabilities, and function from a point-and-click browser, rather than from difficult-to-remember key codes.

Applications-Enabled Softswitch
It is the next category of Class 5 softswitches, the Applications-Enabled softswitches, which bring about a fundamental shift in the manner that the softswitch is implemented by being application-centric versus telephony-centric. These softswitches are architected in a manner that not only allows advanced applications to be quickly introduced but also provides a natural mechanism for interfacing with other hosted applications, both within a service provider's network and the Internet. The applications with these softswitches give service providers new financial reasons for implementing a softswitch, moving from simple cost-reduction, and selling services for less, to significant new revenue generation based on innovative, compelling new services. These applications offer the hosted model of telephony that made Centrex initially popular, but focus on offering advanced PBX functions and new innovative services not typically found on business phones, such as mobile phone features like viewing missed calls, click to dial, or even e-mail a response. End-office users save from $20K to $50K in equipment costs, since they no longer need an in-house telephone system, effectively outsourcing this requirement to a service provider while gaining more control over the management of their telephony on an easier-to-use Web-based portal.

Because applications-enabled softswitches sit at the edge of the network and have an open API with a separate layer for applications, they are ideally suited for development and deployment of many advanced telephony applications. The rich applications combine the benefits of data and telephony to offer new capabilities that users will purchase. Since 80 percent of overall industry revenue comes from voice services, service providers need innovative, voice-oriented applications to generate new sources of revenue. In this highly competitive market with decreasing transport prices and profitability, innovative services that go beyond these basic features are essential for customer retention and increased profits. Additionally, these new telephony applications are designed to be easy to provision by the service provider and/or an office manager at the SMB. The telephony applications on an applications-enabled softswitch can not only be delivered more cost efficiently and quickly than voice transmission, they have greater value to both the service provider and the end-office user.

Feature Servers
There is a small group of applications servers, called feature servers that are often confused with the Class 5 softswitches. However, this group lacks call control functionality and provides the applications only. They are more toolkit-oriented and designed for building
services; they require the addition of a softswitch like
a "POTS/Residential" type to provide call handling
and routing. As a result, the applications that are developed are limited to what the underlying softswitch can support.

Going forward, end-users will demand more applications tailored for special situations such as vertical markets, which are very easy to create on the Applications Enabled softswitches. In today's financial climate, service providers will need the new sources of revenue they can achieve only with these advanced technologies. Thus, the future revenues of the industry may very well depend on these new Class 5 softswitches. It will be important for service providers to determine which application set(s) and which business problems they really are trying to solve when evaluating different softswitches.

Laura Thompson is vice president of marketing and business development at Sylantro Systems. Sylantro's applications-enabled softswitch is designed to allow service providers to deliver high value telephony services. The company's solutions are an advanced breed of managed telephony services that render Centrex and PBX offerings obsolete and provide additional popular capabilities. Sylantro transforms the way communications applications are used and delivered -- doing for telephony what the browser did for the Internet. Visit them on the Web at

Return To The March 2001 Table Of Contents

In Search of Softswitch?

The following companies make up just a fraction of all the vendors listed as members of the International Softswitch Consortium, an organization dedicated to rapid advancement of application development for the evolving Internet protocol networks that support both voice and multimedia communications. Currently, nearly 200 vendors are members of this organization.

A Technical Advisory Council decides which standard interfaces the Consortium will promote. Five standard interfaces are adopted for promotion in the Consortium's charter, including H.323, Session Initiation Protocol (SIP), Real-time Transport Protocol (RTP), Real-time Streaming Protocol (RTSP), and Media Gateway Control Protocol (MGCP). Adoption of additional standard interfaces is expected by the Consortium, allowing powerful call control, media control, authentication, encryption, bandwidth on demand, and policy enforcement on Internet-based multimedia networks.

For more information, visit the International Softswitch Consortium online at


Accelerated Networks, Inc.
AccessLan Networks
Cisco Systems
Comgates Communications
Convergent Networks
empowerTel Networks, Inc.
General Bandwidth
GNP Computers, Inc.
Inet Technologies, Inc.
Integral Access
ipVerse, Inc.
Lucent Technologies, Inc.
Marconi Communications
Mockingbird Networks
Motorola, Inc.
NetCentrex, Inc.
Nortel Networks, Inc.
Nx Networks
SALIX Technologies, Inc. (Acquired by Tellabs) /
Santera Systems, Inc.
Sonus Networks
Sylantro Systems Corporation
Syndeo Corporation
Telcordia Technologies, Inc.
Telecom Technologies (Acquired by Sonus)
TELOS Technologies, Inc.
TeraBridge Technologies Corporation
Unisphere Solutions
VocalData, Inc
Xybridge Technologies

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