InformationWeek

May 14, 2001

IP PBX Basics

By Candee Wilde

traditional PBX is a proprietary telephone-switching system that resides within an enterprise network and connects internal telephone extensions to each other and to the public switched telephone network (PSTN). Vendors program the PBX with applications such as call hold, forwarding, and conference calling, and more complex call-center applications. Because traditional PBX technology is proprietary, customers usually have to ask their vendor to add new applications, and pay for the service. Similarly, traditional PBX vendors usually handle--and charge for--adding, moving, and changing telephone extensions.

Eliminating these expenses for users by using open protocols is cited as a benefit of IP PBX technology by vendors and users. As the name implies, an IP PBX delivers PBX-like services, but over IP-based LANs or WANs rather than circuit-switched networks. IP PBX systems can be designed as a single network server, a group of servers, or a network appliance. Despite widespread use of open protocols, no real standards have been agreed on for IP PBXs, so interoperability between IP systems, phones, and other devices, remains an issue.

IP PBXs began evolving in the mid-1990s, when companies such as Altigen, Dash, NetPhone, Selsius Systems, and NBX introduced PC-, server-, and IP-based alternatives to traditional PBXs, Gartner analyst Rich Costello explains. Soon after, Sphere Communications Inc. announced an ATM-based telephony server system called Sphericall, which was also innovative. Since then, Sphere has added IP support to its product line. Says Costello, "With the subsequent entrance of major new vendors into the telephony space, such as Cisco and 3Com, almost all of these alternative PBX systems have evolved to provide voice-over-IP support in varying degrees."

close this window

E-mail To A Friend | Printer-Friendly | Send Us Your Feedback