IP PBXs scale for the enterprise

By Betsy Yocom, Network World |  Networking

RIP PBXs aren't just small-office playthings anymore. With near-universal agreement that telephony will be carried within IP packets, vendors are preparing their next-generation PBXs with capacities and features they hope will position their products as competitors to classic enterprise-level PBXs.

A Mier Communications survey conducted last month showed that some IP PBXs can reportedly scale to 10,000 stations, whereas a year ago the average system supported a maximum of 50 to 100 stations. Mier Communications also found that the market is segmented into low-, midrange and high-end systems.

Vendors of classical PBXs have also entered this crowded field by adding voice-over-IP gateway cards and modules to "IP-enable" their existing PBXs.

As far as features are concerned, all vendors are branching out from basic PBX features such as hold, wait and transfer, by adding more advanced PBX features like modem relay and fax support, interactive voice response, billing and accounting, direct-inward-dial, elaborate call routing, least-cost routing and toll restrictions.

Miers detailed questionnaire went to 36 vendors that we believed were shipping or planning soon to ship IP PBX products. The systems go by a variety of names, including Telephony-over-IP exchange, Integrated Communications Server and IP Telephony Server.

We received 22 responses. However, not all were complete and some of the products didn't quite fit, so several were disqualified. The final participating vendor list was: 3Com, Alcatel, Cisco, Dialogic, Ericsson, Intecom, Inter-Tel, Avaya/Lucent, Mitel, NEC, Oki Network Technologies, Shoreline Communications, Tek Digitel, Vertical Networks, Vovida Networks and Vive Synergies.

Expanding capacities

As recently as late last year, IP PBXs generally supported just 100 or fewer stations and were targeted mainly at small-office and branch-office applications. We define "stations" as any connected device, including phones, PCs, faxes and others. Today, however, only 25% of the products surveyed top out at 100 stations. Approximately 30% support maximum capacities in the 101-to-216-station range, and nearly 20% support between 1,000 and 5,000 stations. Products in this midrange group include Lucent's Definity; Alcatel's OmniPCX 4400 and the Shoreline Communications System.

On the high end, there are systems that can support thousands of stations. For example, Cisco's AVVID can reportedly support up to 10,000 stations, and the company claims it is aiming at 100,000 users within the next five years. Cisco's AVVID targets the same high-end enterprise users as traditional PBX vendors such as NEC and Intecom do with their IP-enabled PBXs, but AVVIDD is based on an entirely different architecture. Cisco advocates replacing the traditional fixed-bandwidth, time-division multiplexed PBX switch fabric with a distributed IP network.

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