Softswitch Fever: The Bedrock for Next-Gen Services - Technology Information

Telecommunications, Jan, 2000 by Doug Allen

Of all the elements that will make up the new public network, softswitches may be the most important. Softswitches play a crucial role in converged services, end-user control and third-party application integration--attributes that require many changes to the infrastructure.

The idea isn't new, even if the buzzword is. The idea of supporting advanced intelligent networks (AIN) has been around since the '80s, when proprietary code and lack of vendor support sank it. This time around, softswitches have generated major hype--and some real-world deployment. Level 3 and Global Crossing have announced major IP telephony initiatives using the technology; 22 vendors have announced or introduced softswitch products of one stripe or another; and the International Softswitch Consortium debuted earlier this year to address time-to-market issues for its impressive roster of members.

So what is a softswitch? Everyone basically agrees that a softswitch separates the call control functions of a phone call from the media gateways (transport layer) that carry it. Call control features can vary, but call routing, admission control, connection control (such as creating and tearing down sessions), and signaling interworking--such as from SS7 to SIP--are usually the minimum requirements. Since a softswitch is essentially software that resides in either a server or in another network element, SS7 functionality can be embedded or kept separate. As a general rule, tighter integration is usually better. And just to complicate matters, the softswitch can sit on top of a media gateway, instead of being physically distinct, as long as transport and call control features are split. This is the case with Salix Technologies, which offers a "class independent" switch with embedded signaling, and Convergent Networks, which splits the call control chores between its ICS switch and a service management gatewa y.

By creating separate planes for control and switching and leveraging software's programmability, service providers can combine transport services and control protocols freely and migrate from one service to another. Most importantly, open APIs allow new services to be introduced to the switching scheme, and the old Class 4 and Class 5 services are retained via SS7 links.

Both a server-based and switch-based model have advantages, and a combination of the two will probably prevail. According to softswitch start-up telecom technologies' Matthew Johnner, director of product marketing, "We leverage the switch-centric model to increase performance on resource-intensive tasks such as table lookups and state control (the management of the status and handling of a call as it relates to origination, termination and associated features within a CLASS-based switch). On the other hand, a server-based approach is more powerful than a switch-centric architecture for programmability of procedural functions such as policy-based decisions, subscriber preferences and feature control?"

Several vendors have gone a good deal further in their definition. Most point out that open APIs are of no use to providers without a service creation environment (SCE) that supports new applications or modifies existing ones. Moreover, a library of existing services should be available, so that network managers don't have to reinvent the wheel each time a new service that combines aspects of previously available services is rolled out. Unisphere Solutions, which abosorbed Castle Networks, has announced plans to wrap OSS links, metadirectories, service provisioning and firewall control to the usual feature menu, along with service mediation and service creation standards such as XML and Java. telecom technologies' laundry list includes a signaling gateway, call agent or call session engine, a policy/directory server, an IP telephony gateway, a network manager and an SCE.

Cost Justification

There are three primary advantages to using a softswitch. As mentioned before, users become independent of vendors and their technology-centric approach (e.g., ATM, IP, TDM) and the protocols hey support (e.g., H.323, MGCP, SIP). Providers gain more control over service creation, where the true telephony wars will be fought, and the software reduces the total cost of service rollout.

"A softswitch is generally 40 percent to 45 percent less expensive than a comparable circuit switch, scales better, and--most importantly--is an open platform for innovations to take place," said Mike Borsetti, director of technology strategy for NorthPoint Communications. "Furthermore, because softswitches utilize general computing architectures where price/performance has historically improved at a rate of 60 percent to 80 percent per year (Moore's law), we expect them to provide an even greater cost advantage than circuit switches, where price/performance improvement has been only around 20 percent per year." Indeed, many vendors predict and welcome the onslaught of a new thirdparty developer cottage industry that will create standards-based services that can fit into any network easily and quickly, bringing time-to-market into the two-to four-week implementation range.