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Softswitch Defined
Charlotte Wolter
05/01/2000 Posted 05/2000 Softswitch Defined Softswitch. The term is deceptively simple, deceivingly straightforward and used everywhere. However, its real meaning has been as hard to grasp as a puff of smoke, and discussions about what a softswitch is, or even whether such an entity exists, have become contentious among observers of the new telephony landscape. Whether or not there is ever agreement on exactly what a softswitch is, it is unlikely that the term will go away. For one thing, there is an organization called the International Softswitch Consortium (www.softswitch.org) that comprises most of the vendors and service providers addressing converged voice and data communications. For another, the term, despite its imprecision, captures the essence of what is hoped and planned for new packet-based public networks--that hardware and features alike will mirror the distributed architecture, software-driven generic platforms, and plunging costs of computer systems--the original model for "soft" processing platforms. Most importantly, there are actual products. A few are on the market already and several dozen have been announced. The products are either being called softswitches or claim to perform the functions, specifically call control, of a traditional telephone switch. These new products will further define the softswitch arena, and extend it as flexible, distributed switching architectures are adapted for a range of communication applications. Defining Moment Softswitch, media gateway controller, call agent, gatekeeper: These are the varied nomenclatures that have been attached to the products that perform the functions that are coming to be called softswitches. Gatekeeper is the ancestor term, derived from VoIP systems in which gateways converted the voice and signaling from analog PSTN and SS7 to IP packets. The gatekeeper controlled one or more gateways, guiding the setup and teardown of voice circuits between the two kinds of networks. Media gateway controller is an elaboration of gatekeeper, growing out of the first efforts to standardize the control of media gateways using a protocol called media gateway control protocol (MGCP). Call agent is a highly generic term that attempts to describe all systems that handle call-control functions. The term "softswitch" is almost as generic as call agent, but seems to be winning out over that term because it is more descriptive of the way these systems generally are designed as software running on a standard computing platform. Analysts and potential users have widely differing views of what constitutes and defines a softswitch, with call control being the unifying principle. "Essentially, it is a decomposed call logic from a traditional central-office type of switch," says Tom Valovic, research manager for data communications and service provider infrastructure at International Data Corp. (www.idc.com). "Through multiprotocol interoperability, it can direct the switching activities of media gateways, which can encompass a lot of different products." Those media gateways do not have to be collocated with the softswitch. The only communication between them is signaling to set up a call and/or a calling feature, which is a low-bandwidth communication. The softswitch may set up the path or do a database dip, but the gateway controls the flow of the medium--whether it is voice or data--over the path. Scott Davidson, executive director of VoIP products for Telcordia Technologies Inc. (www.telcordia.com), says, "If we have limited space in a central office, the only thing that we have to put there are gateways. The actual call agent system can be in a data center." This would appeal to CLECs, he says, giving them "the ability to support lower density markets without having to deploy expensive equipment or backhaul voice traffic. They have to deal only with signaling traffic, and there's a huge difference in bandwidth and cost." Hilary Mine, executive vice president, Probe Research Inc. (www.proberesearch.com) and a leading consultant in IP voice, categorizes the functions of a softswitch as falling into four different layers:
In this model, while call control and routing are the primary objectives, there are protocols to enable a number of different devices to cooperate, especially media gateways, and a mechanism to create complex call features and applications on top of basic call control. That mechanism is sometimes called a feature server or application server, depending on the vendor. "A key point about softswitches: It's not about voice only," says Mine. "It's the central applications development environment and call agent for the reinvented converged multimedia public network [voice, video and data]. A second important point is that there will be multiple business models for softswitches. Some providers may be ASPs rather than vendors. Already there are Internet call waiting and unified messaging portal companies that are potentially on a path to becoming your local service provider using their own applications and call control software married to other people's gateways [outsourcing to Level 3 Communications Inc., www.level3.com, or Williams Communications, www.williamscommunications.com , networks, for example]. The softswitch concept--the fundamental separation of call agents and applications from the underlying media transport--is what will make it possible for [America Online Inc., www.aol.com] or Yahoo! [Inc., www.yahoo.com] soon to be your full-service telco." Ike Elliott, senior director of voice network engineering at Level 3 Communications and one of the founders of the Softswitch Consortium, considers softswitch an "umbrella term, and call agent and media gateway controller are subsets, though call agent is pretty broadly defined as well." He also points out that in some networks, softswitches don't necessarily control gateways. "They can also control an MPLS-based routing network that doesn't have any media gateways on it." In that instance, the softswitch sets up calls between two endpoints that don't know how to find each other. Jason Sayers, senior technologist in the office of the chief technology officer at Williams Communications Group Inc., offers a more telephony-centered definition. "It is an application that is trying to emulate circuit switching using a packet-based infrastructure, and it does that using various gateways. It is the brains that does the call processing. There are different levels of call processing that softswitch makers are doing, from just '1-plus' dialing or '800' to more complex." The problem, says Michael Howard, CEO of consulting firm Infonetics Research Inc. (www.infonetics.com), is the vendors that have announced product have slightly different, but often overlapping, features. "Sonus [Networks Inc., www.sonusnet.com], SALIX [Technologies Inc., www.salix.com], Tachion [Networks, www.tachion.com], etc., all have chosen to carve out slightly different function sets, so they solve different problems. None of them do all the functions of a PSTN switch." Reinventing the Public
Network By contrast, Lucent Technologies Inc. (www.lucent.com), which actually named its product Softswitch, has a huge product with a price tag around $1 million that does many of the functions of a typical Class 5 switch, including some very obscure calling applications. 2nd Century Communications Inc. (www.2c2.com), a Florida-based CLEC, is doing mostly what it calls mediation, translating calls from a circuit-switched to a packet-switched network and back. The company is using the MainStreetXpress 36170 switch from Siemens Information and Communication Networks Inc. (www.icn.siemens.com) and the PathMinder softswitch from TeraBridge Technologies Corp. (www.terabridge.com). "The lines blur," on whether or not this is a softswitch says Vince Rocca, CTO and co-founder of 2nd Century. "A mediation switch is very nonintelligent. All it is doing is saying here is the legacy network and here is the next-generation network and you have to do a minimal amount of conversion to get between the two." A softswitch, however, gets into the applications. Though 2nd Century is doing "a lot of mediation and a few applications, we will migrate to more applications as time goes on, and will need a different platform for that." The current model used by 2nd Century pushes much of the intelligence to the edge, Rocca says, using an IAD by VINA Technologies Inc. (www.vina-tech.com) as customer premises equipment. "Softswitches, to me, are really taking a lot of intelligence and centralizing it in the core of the network. The difference between a mediation device and softswitch, in my mind, is that a softswitch will try to duplicate at some point the majority of the features that we find in a Class 5 switch or even augment them." Adding another complication to the definition of a softswitch is that gatekeepers can be considered softswitches because they are able to do some call control functions. Companies such as Clarent Corp. (www.clarent.com), NetSpeak Corp. (www.netspeak.com) and VocalTec Communications Ltd. (www.vocaltec.com), who have been shipping product for some time, can move their products into the softswitch arena as Class 4 replacements, Mine says. At this point, these views are largely a matter of opinion because so few softswitch-type products have actually been deployed and used with live customers. Probe Research recorded no shipments of product for the year 1999, and Lucent may have just shipped to Level 3, Mine says. Williams Communications, which has used the Sonus product mainly for call mediation in a Class 4 environment, plans to field trial a full Sonus system, including softswitch, gateways and feature server, in three cities by mid-2000. Even that trial, however, will likely encompass only beta users and may handle very little live traffic. Issues Remain With products just at the announcement stage or in beta trials, some issues are emerging about what softswitches should or should not do, depending on the applications. The differences of opinion highlight the highly eclectic network environment that this new class of product will be entering and the sheer variety of new network features that are emerging as converged voice and data are shaped to many applications. Feature servers are the newcomers to the softswitch landscape, emerging as a repository for applications and databases that can be used to deliver services above and beyond the simplest call control. But the term is deceiving, because a feature server is not a discrete entity, but rather may be any number of servers spread out over one or more networks that can be accessed to deliver services. One of the emerging issues is whether features have to be on the softswitch itself or relegated to a feature server, and where to draw that line. In the PC model there are operating systems and applications, and they are clearly separated. However, an operating system often includes basic application functions, such as the ability to display pictures and play audio. Likewise, on a softswitch, there are certain applications, such as basic call routing, where it is difficult to segregate them from the call agent because of state issues. "There are many different service providers with different service plans" that will want to draw the line between the softswitch and the feature server at different places, Mine says. "Some will want something like Castle Networks [Inc.], which originally put all functionality in the gatekeeper. The call control and applications were all in one box. Taqua [Systems Inc., www.taqua.com] also has applications in the gateway." Castle, now part of Unisphere Solutions Inc. (www.unispheresolutions.com), currently offers a separate softswitch. For a CLEC that has a small deployment and does not want to do extensive engineering, it may be more attractive to have a plug-and-play box that does everything. However, "if you are AT&T and you have architected a very sophisticated network with a lot of service types and a lot of service creation functions so others can program to it ... and you want your network to be access network agnostic, then you are going to need more separation" of functions, Mine says. A vendor that has a softswitch that does basic applications may want to partner with a vendor that has more enhanced features and can be used as a feature server, says Sayers. He expects some vendors will begin to call their products feature servers. Some vendors are building switch-based softswitches versus server-based softswitches. In the early days of VoIP gatekeepers, "they had the features on a server off the switch. It was not a smart design but it served the purpose at the time," says Chris Aronis, a consultant with Network Strategy Partners LLC (www.nspllc.com). Some smaller players are still doing this, he says, "but we will find that the majority are switch-based in the foreseeable future." Packet
Voice Network Functional Architecture A number of new market entrants in 2000 will introduce products that do not have their own gateways. Instead, they will have powerful switching fabric control and a rich set of applications on a feature server. They will partner with gateway providers. New players doing this include ipVerse Inc. (www.ipverse.com), NetCentrex (www.netcentrex.net) and Sylantro Systems Corp. (www.sylantro.com). Others have announced only gateways so far. These companies include Cisco Systems Inc. (www.cisco.com) and Zhone Technologies Inc. (www.zhone.com). There are ongoing efforts, such as the Cisco New World Ecosystem Partner program, that are working to establish interoperability among gateways and softswitches. Although MGCP will be the protocol that will eventually be used for this effort, it is just nearing completion. Most vendors have not implemented an interoperable version and, instead, have its predecessors, such as Internet device control protocol (IDCP) and simple gateway control protocol (SGCP), implemented. "This is interesting because it means there will be vendors that can focus on enhanced services, such as unified messaging, customer control of provisioning and call center functions," says Sayers. "They are focused on the softswitch and not necessarily the media gateway." Although the first thing Williams tests is basic call functionality, he says, "the vision doesn't elude us as to where this could go as we get more and more features into a softswitch. Davidson points out that separating gateways and softswitches supports one of the goals of the new architecture--a medium-independent approach. "We have worked recently with cable companies, which is a hybrid fiber/coaxial medium, but we could just as easily support DSL or fixed wireless or even straight Ethernet. We just need to be able to deliver the signaling protocol to end devices." Originally envisioned to replace the monstrous Class 5 switches, softswitch platforms, by recent estimates, can be as much as 20 times smaller physically and 10 times cheaper. In that vision "they are the services engine of the converged IP telephony network," says Howard, which can obviate the need for a Class 5 switch. "They are services engines that work for both the PSTN and IP networks. They apply not only existing Class 5 features and business functions but new business functions as well." However, the flexibility of the platforms is beginning to be realized as new networks are established for chores, such as building an all-data network and adding VoIP to it, or offloading Internet traffic from Class 5 switches. "For other selected markets, such as business data and e-business voice services, you don't get thousands of features of a Class 5 switch but basic business features," Howard says. An example is Tachion, which calls its product a Class 5 switch in a box, although now it has only the most popular business applications rather than the full Class 5 slate. Williams will use its deployment of Sonus primarily as a media gateway and signaling gateway, says Sayers, as well as for Internet call offloading and "800" services. "One possibly then would be used as we build out our local strategy as a classless switch." Still, a CLEC today is unlikely to buy a Class 5 switch for a new buildout in a city, he says, and will likely go with a softswitch solution. Given that they often replace Class 5 infrastructure and provide new ways to offer voice services, does a softswitch have to include a gateway for TDM voice? The question goes to the heart of what is supposed to be happening with converged networks. "If it is about a converged network, then the role of the softswitch becomes more interesting," Mine says. "If a softswitch is just replacing intelligent networking [IN] things, if it's just cheaper IN, it's nice but it doesn't give a real competitive advantage." NetCentrex is one of those not offering TDM phone, though there is nothing in its softswitch to prevent it from partnering with one of the many TDM gateway providers. As for reliability, the hallmark of the Class 5 infrastructure, service providers are not necessarily looking for "five 9s" performance yet. "I can't say that we do that on a blanket basis," says Elliott. "There are certain applications that need it, and others that do not. The more they can reach that level, the greater the appeal to the customer base. However, there is a kind of spectrum. At one end, a service provider could get away with 95 percent depending on what customers are paying, such as some of the free-phone services. But, if customers are paying, you have to be a little better." Today, the market for softswitches is limited to startups, CLECs, some ISPs and a few big players such as Williams and Level 3. As far as taking off in the ILEC community, "it is still in the planning phase," and may be for some time, says Paul Langmeyer an analyst with RHK Inc. (www.rhk.com). "It is amazing how far behind the RBOCs are and what a low priority it has become," he says. The exceptions are pioneering big players, such as Global Crossing Ltd. (www.globalcrossing.com), Level 3 and Qwest Communications International Inc. (www.qwest.net). "It will be a very slow transition," he adds. Even in the big users, most softswitches today are doing Class 4 functions, such as Williams' use of Sonus and 2nd Century's deployment of the Siemens mediation switch. When they will move out of those roles is unclear, but there are indications that 2000 will see a number of real-world network deployments, possibly announced at SUPERCOMM. Despite Wall Street's predictions of billion-dollar markets, vendors are still struggling to make sales, Langmeyer says. Instead, "this is embryonic," but all the hype "has become very confusing to a lot of sectors of business," he notes. "When I start seeing things such as a network with 100,000 subscribers with a number of vendors' platforms, then that will be credibility that those guys are for real," Langmeyer says. "Right now, all we see is small-scale stuff with big plans."
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