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Centrex, IP Style

But if you also want to access voicemail, place calls from your browser and gain easy Web conferencing and instant messaging capabilities, look no further than an IP Centrex service. For a small-to-midsize business torn between maintaining a PBX and outsourcing, the cost will likely be on par, but IP Centrex will offer you more features (for more on how to choose, see "The Business Case"; and for an overview of a company with a mix of Centrex and PBXs, see "Fidelity Matches Phone Service To Employees' Needs").

To determine just how far IP Centrex has come and what features providers are offering, we asked GoBeam, ICG Communications, MCI and Verizon to participate in our tests. Only Verizon declined our invitation, citing "huge" internal costs to support the test.

Service Providers' Top 10 Requested Apps

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Testing 1, 2, 3

We asked the providers to supply us with a phone and access to their switches so we could look at features and functionality. Each participant sent us a Cisco IP phone, though the providers support a wide range of phones, including those from Polycom and Pingtel.

Our worst-case test network used an unmanaged ADSL connection. We set up a single public IP address at the router, while the rest of the network was privately addressed with static and DHCP-assigned addresses. Because the broadband connection was unmanaged, the phone traffic had to contend with our e-mail, FTP and HTTP packets for bandwidth. Internally, the calls were forced to compete with NFS (Network File System)-mounted partitions providing MP3 and MPEG-2 files around the network.

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