In this Clear Choice test of four open source-based IP PBX systems, we found products that are well suited for the low end -- defined in this testing as supporting as many as 250 concurrent users. By providing simple installation processes, automatic endpoint configuration and straightforward Web-based management interfaces, these products could go a long way in easing IT fears about dealing with open source VoIP products.

While this initial test of these products focused on smaller-scale deployment models, several of the systems tested also lend themselves to larger deployments. They incorporate more-advanced features, such as standby systems for failover and presence capabilities. All provide full Session Initiation Protocol (SIP) support for endpoints as well as trunks. The management interfaces are simple but also provide detail for troubleshooting and bandwidth control necessary in larger environments.

The vendors that accepted our invitation were Escaux, Fonality, Four Loop Technologies and Pingtel. Three of the four products tested (PingTel is the exception) were built on top of Asterisk, the original open source IP PBX (see the assessment of Digium's Asterisk). The four vendors in our test demonstrated tangible improvements to existing open source IP PBX base code, especially in their efforts to facilitate installation, management and maintenance with GUIs.

The systems were ordered and provisioned as a customer would procure them. We then put them through their paces looking at management, features, interoperability, ease of use and architecture. Because such performance metrics as voice quality depend on the endpoint chosen, it was not a key factor in this test.