Calling all IP PBXs.

This article evaluates several Internet protocol (IP) private branch exchanges (PBX). The 3Com, Avaya, Siemens, and Zultys IP PBX were tested at the Advanced Network Computing Laboratory at the University of Hawaii. Each product provides all the familiar telephony functions, from putting people on hold with insipid music, to transferring calls and recording voice mail. But each has capabilities that go far beyond the basics. Even better, these PBX can send phone settings out to the telephone sets attached to the network, providing great control over how the phones work, which features are available to which users, what locations the phones can call and how the phones can be used. The Siemens HiPath 4000 is another mega-PBX that can he configured to support as many as 100,000 users if several of the units arc networked together. The individual HiPath 4000 that we tested can support up to 12,000 users. 3Com VCX V70 provides a Web-based interface for phone users, allowing them to set various parameters for their phones. This means that they can use the Web interface to set up button assignments, forwarding rules, speed dial numbers, and so on. Avaya's S87OO is scalable enough to handle nearly any enterprise. Properly configured, this PBX can support up to 36,000 users per server and up to 1 million by networking multiple servers together. The S8300 is much smaller, limited to 450 users per server or 28,800 per network. The company Zultys says that the MX25O was designed from the ground up as an IP PBX platform, rather than being a telephony platform with IP grafted on, or a computer with telephony grafted on. INSET: Prepping for Networked Telephony.