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Feature Article
September 2001

Let There Be (More Than Just) Light


What happens when you flip on the softswitch? After the marketing bubble-wrap and engineering Styrofoam have been pulled away, what is this piece of equipment going to do for you? A few years ago, you might have been satisfied to have it manage the setup of a carrier quality voice call over a packet infrastructure, using any reasonably cosmopolitan media gateway control protocol. But a lack of precision in the initial definitions of a softswitch combined with the intoxicating rush and subsequent crash of funding sped a roller coaster ride of expectations. This is a good time to step back and assess where the action is today in softswitch deployment and where tomorrow's development is likely to take it.

According to legend, one of the first comments received by IBM researchers upon the unveiling of their new invention of the microchip in 1968 was "But what is it good for?" The birth of the softswitch was greeted with no such lack of imagination. While the academics debated the requisite degrees of "softness" (hardware independence), "openness" (reliance on standard protocols), and other criteria in competing softswitch definitions, pragmatists raced to market with demonstrations of compelling value.

The first intrinsic value provided by the softswitch is in network "flattening." Because the bandwidth required for the packets that contain the bearer path or voice encoding of a call is anywhere from 50 to 5,000 times that of the signaling required to make and take down the connection, the softswitch's role in separating these two communication channels profoundly shifts the capital and operational expenses of legacy voice-centric networks. No longer is a dedicated mesh of "fat" voice-only pipes required to interconnect each switch in the network. By consolidating voice and data traffic at the customer site on one link, virtually eliminating trunk provisioning, and simplifying operations, service providers have seen access cost savings of up to 35 percent and operational cost savings of up to 50 percent as well as up to 85 percent faster deployment.

A second benefit that flows directly from the softswitch's delegation of bearer control to the media gateway is the greater geographic span of a given instance of network intelligence. With a five- to ten-fold increase in the number of air miles between a softswitch and a media gateway, we have seen a 25- to 50-fold increase in the serving area of a softswitch. This greatly reduces both the costs of geographic expansion as well as the time it takes to deploy new services.

A third de facto benefit from carrying bearer path over packet is that it allows traffic to skirt taxation and other regulatory barriers in certain areas of the world. Some of the initial European deployments of softswitches were able to make compelling business cases through the promise of the avoidance of burdensome tariffs alone.

So three of the key benefits of softswitches derive simply from their role in enabling carrier class voice over packet networks. Nevertheless, as these early promises of softswitches became well known, a cycle of increasingly exuberant expectations was established. First, came the purists' drive for 100 percent software switches based on commercially available hardware. We have seen early adopters of this approach already reap the benefits of Moore's Law by migrating onto newer generations of hardware offering better price/performance between Beta trial and General Availability. Second came the open architecture advocates' promises to meet and exceed Class 5 service sets on the basis of an ever-increasing litany of new protocols and hordes of eager third-party software developers. Third, and perhaps most important, was the ability of the softswitch to lower the barriers to entry for "greenfield" opportunists in the world of communications. As the expectations multiplied, so did the number of vendors: By mid-2000, dozens of vendors had unveiled new entries, and the International Softswitch Consortium had 185 members.

Over a year later we see a comparatively modest set of real world deployment scenarios for softswitches. Least ambitious, but perhaps most widely touted are Internet Offload deployments, where media gateways controlled by softswitches actually route TDM dial-up modem traffic onto stripped down PRI trunks for cost savings. Independent analysts are now saying this market has already peaked, due to the decline in new ISP subscriptions and overcapacity in DSL and Cable access, which are alternatives to dial-up. Second, but perhaps less publicized, are the 'toll bypass' solutions that have seen greater success outside of North America, where comparatively high rates for long-distance and especially international long-distance offer more favorable arbitrage opportunities. Slower to develop are the carrier class end office replacement softswitches.

Several roadblocks have emerged to slow the progress of softswitch deployment. First, while a basic VoIP call can be emulated in the softswitch fairly readily, there is a mountain of non-trivial specializations that lies between a basic call and full Class 5 transparency. The incredible complexity of design assumptions accrued over decades of connection-oriented networks do not seamlessly graft onto a connectionless network. Among the boulders at the foot of this mountain lie such showstoppers as emergency (E911) and CALEA or Lawful Intercept (wiretapping). While marketing adrenaline was diverted toward the revolutionary possibilities of the softswitch, these relatively unglamorous table-stakes requirements did not necessarily get the right priority.

Beyond design issues, archaic inter-LATA transport restrictions obviate some of the network flattening capabilities of softswitches for the regulated service provider space. Also, the TDM entrenchment within inter-company billing resolution mechanisms continues to hamper the full flowering of next generation possibilities.

While vendors reassure the industry that solutions for all these hurdles are eminent, it is clear that some of the initial luster and simplicity of the softswitch vision will be difficult to reacquire. For example, CALEA requirements are more appropriately met not by a softswitch but through dedicated media servers, just as SS7 network interworking usually scales better on dedicated gateways. While the softswitch continues to be a focal point within the network, it is clear that it has helped create a world in which the 'switch' has more limited importance as it devolves into a family of specialized servers. As the dreamlike vision of softswitches becomes somewhat scaled back, many of the more exuberant early expectations are finding a new home in one of its spin-offs -- the SIP-based application server.

We have seen a tendency for new technologies to devour or co-opt the spin-offs they enable. The story is so old and universal it was captured in the ancient Greek myth of Kronos, the leader of the Titans. When Kronos was foretold that his son would overthrow him, he began a habit of swallowing his newborn children. Eventually his wife tricked him by presenting a stone wrapped in swaddling clothes, thus saving her newborn son. This son grew to be Zeus, who upon reaching maturity, overpowered Kronos and himself became the king of gods and men.

Similarly, as new possibilities enabled by softswitches have emerged, vendors have been eager to swallow these into their existing softswitch product descriptions. But just as in the myth, there comes an idea that is too revolutionary to be fully absorbed by the earlier model. For softswitches, this "problem child" may be SIP, the Session Initiation Protocol.

SIP is an application-layer protocol that allows direct peer-to-peer communications between intelligent clients without the need for centralized call control. The SIP architecture is articulated entirely through the vocabulary of Web-based application development. Therefore, SIP is poised to change how people communicate just as HTTP and Web browsers changed how people use the Internet. Because SIP treats voice, video, and data the same, it can deliver as an effortless byproduct the perennial white elephant of telecom: Spontaneous video calls. While SIP's ascendancy over H.323 in the enterprise is increasingly accepted, its potential to disrupt carrier-based communication services is perhaps even more dramatic.

Note that increasing client intelligence is not a death knell for core networks. As we have seen in the evolution of Web applications, applets (client-based intelligence) eventually fuel the creation of servlets (server-based intelligence). This trend has gone so far as to create a renaissance for mainframe computing as industrial strength Web servers over the past few years. So network-based server intelligence as provided through SIP-enabled application servers will be an exciting growth area over the next few years.

As we have seen, softswitches provide compelling value for streamlined communication networks. SIP provides an evolution of communications into peer-to-peer multimedia. While dedicated SIP application servers are rolling out under their own banner, we also see softswitches being positioned as SIP servers.
The de-evolution of the switch is spawning increasingly specialized servers, and SIP is likely to accelerate that trend. In addition, SIP's ability to span different
network types will help further the differentiation of SIP-enabled softswitches dedicated to different markets. Together and apart, softswitches and SIP will continue to accelerate the transformation to the next-generation network.

Jim Thomas is senior manager, Carrier Voice over IP Marketing, Nortel Networks. Nortel Networks is a global Internet and communications leader with capabilities spanning Optical Internet, Wireless Internet, Local Internet, eBusiness, and Personal Internet.

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