What's in a name?

Some providers object to the IP Centrex terminology and insist on calling the service network-based IP telephony. To them, the term "Centrex" carries too much baggage: It sounds dated, and it is associated with the old regional Bell operating company monopolies.

"Centrex was the poor-man's PBX, while IP Centrex is better than a PBX," says Kevin Gavin, chief marketing officer for IP Centrex pioneer GoBeam.

To further confuse things, the incumbent local exchange carriers are rolling out a "Centrex IP" service that primarily is a migration platform for traditional Centrex customers. While IP Centrex uses softswitch technology, Centrex IP is a hybrid platform that's is based on a Class 5 TDM switch that has been IP-enabled. BellSouth and Qwest are sticking with this Centrex IP technology for their initial trials.

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Some providers object to the IP Centrex terminology and insist on calling the service network-based IP telephony. To them, the term "Centrex" carries too much baggage: It sounds dated, and it is associated with the old regional Bell operating company monopolies.

"Centrex was the poor-man's PBX, while IP Centrex is better than a PBX," says Kevin Gavin, chief marketing officer for IP Centrex pioneer GoBeam.

To further confuse things, the incumbent local exchange carriers are rolling out a "Centrex IP" service that primarily is a migration platform for traditional Centrex customers. While IP Centrex uses softswitch technology, Centrex IP is a hybrid platform that's is based on a Class 5 TDM switch that has been IP-enabled. BellSouth and Qwest are sticking with this Centrex IP technology for their initial trials.

Another option called managed or hosted PBX can be based on traditional or IP PBX switches.

There is some disagreement about where the switch has to be or who has to own it if it is to qualify for this classification.

However, what distinguishes Centrex - traditional or IP - is that there are multiple tenant-customers sharing the same central-office switch. With hosted or managed PBX service, the switch is dedicated to a single customer, regardless of the switch's location or ownership.

In the main story, IP Centrex and network-based IP telephony are used interchangeably.

Read more about voip & convergence in Network World's VoIP & Convergence section.