Class 5 Switches

By Ellen Muraskin  |  Posted 2004-05-26 Print this article Print

Class 5 switches, situated at the local central office—the user end of the switching office hierarchy—traditionally supply the enhanced features the calling public has come to know: caller ID, three-way calling, call blocking, last-call return, call waiting and the like. Class 4 services link trunks together for aggregating traffic across longer distances and handing off calls between carriers.
Signaling gateways link up an IP-based phone system to the PSTN world, so that things such as caller ID can be delivered in, and things such as 800 numbers can be delivered out to the routing tables that know where such calls terminate.
Click here to read an interview with one of the founders of the SIP protocol, who responds to VOIP security concerns. In a Monday morning conference call, Janet Davidson, president of Lucent Technologies Integrated Network Solutions (INS), pointed out that Telica has done well both with carrier customers replacing their legacy Class 5 switches and with those "capping and growing" their Class 5 business to extend past the limits of TDM switches. "Their products give us a more complete, highly scalable VOIP solution and a flexible, open architecture to respond to the many different approaches our customers are taking with the evolution of their networks," Davidson said. Ron De Lange, vice president of Lucent Technologies Convergence Solutions Group, described a target carrier customer as one who wants to position signaling gateways and media gateways in distributed fashion out of regional hubs, in areas of greatest end-customer density, all controlled by centralized media gateway controllers/softswitches. Lucent spokesman Michael Alva went into some specifics on Telicas line: The Plexus 9000 Media Gateway simultaneously supports both IP and ATM transport and wireline and wireless applications, critical to Lucents carrier customers. At 21,500 ports, it also complements Lucents 8,000-port Universal Gateways, as well as the PSAX Multiservice Gateways, which are used primarily in wireless backhaul applications. "We will continue to support all of these gateways because they remain appropriate for different customer applications," he said. "The Telica PLUS Signaling Gateway, because it is designed for a distributed environment, complements the Lucent softswitch and will help speed delivery of Class 5 VOIP applications based on the Lucent softswitch." "The PLUS Media Gateway Controller–which supports 10 times the capacity of first-generation packet media gateway controllers—overlaps our unified softswitch," Alva said. "Going forward, we will integrate PLUS MGC and Lucent Softswitch functionality as appropriate." Alva also nodded to the importance of interoperability with the phone systems of other vendors, both carrier- and enterprise-directed. In that regard, he pointed out that the Lucent Softswitch and the Plexus 9000 platform are fully interoperable with other softswitches, trunk gateways and line gateways that support open signaling interfaces including MEGACO, MGCP, SIP, and SIP-T. They also support legacy protocols such as ISUP, TCAP/AIN and GR-303 for seamless integration with the TDM switches. Check out eWEEK.coms VOIP & Telephony Center at for the latest news, views and analysis on voice over IP and telephony.

Ellen Muraskin is editor of's VOIP & Telephony Center. She has worked on the editorial staff at Computer Telephony, since renamed Communications Convergence, including three years as executive editor. Muraskin's work has also appeared in Popular Science magazine and other publications.

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