VoIP variations

Different architectural strokes from different vendor folks.

When it comes to IP PBXs, products from IP-centric vendors and legacy PBX companies are characterized as much by their differences as by their similarities.

In general, the two camps can be summarized this way: the legacy PBX vendors include Alcatel, Avaya, Mitel, Nortel and Siemens; the IP newcomers are led by Cisco, 3Com, Shoreline and Vertical Networks.

The legacy vendors have an edge when it comes to the total number of traditional PBX features. The IP PBX vendors offer a more stripped-down suite of features - call hold, call forwarding, call waiting, conference calling and voice mail. But the newcomers also take advantage of the tighter integration with desktop productivity applications, such as Microsoft Outlook, giving users a unified view of voice mail, e-mail and faxes.

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When it comes to IP PBXs, products from IP-centric vendors and legacy PBX companies are characterized as much by their differences as by their similarities.

In general, the two camps can be summarized this way: the legacy PBX vendors include Alcatel, Avaya, Mitel, Nortel and Siemens; the IP newcomers are led by Cisco, 3Com, Shoreline and Vertical Networks.

The legacy vendors have an edge when it comes to the total number of traditional PBX features. The IP PBX vendors offer a more stripped-down suite of features - call hold, call forwarding, call waiting, conference calling and voice mail. But the newcomers also take advantage of the tighter integration with desktop productivity applications, such as Microsoft Outlook, giving users a unified view of voice mail, e-mail and faxes.

When it comes to other characteristics, such as basic architecture, how they provide reliability and how they support standards for features such as call control and inline power, the results are all over the map.

IP phone home

You might assume that all IP PBX vendors support IP phones, but until recently, that was not the case. The legacy vendors supported IP phones, but not upstarts Shoreline and Vertical. They held the view that the value of the IP PBX lay with the distributed architecture and the applications, not an expensive phone. Therefore, they limited their support to analog stations.

Another concern often raised about IP phones is the potential need to reengineer the corporate IP network to accommodate - and prioritize - voice traffic. Establishing quality of service entails configuring switches and routers to support 802.1p/q, type of service bits, and potentially, Differentiated Service. While these are not necessarily difficult tasks, they do require datacom expertise - either in-house or outsourced.