Over a two-month period, the VoIP analysis tools were connected into our test bed made up of four IP PBX systems, which were:

•  EADS Telecom's Nexspan L system, which uses a proprietary, stimulus-based VoIP call-control protocol.

•  Mitel Networks' SX-200 ICP, which uses a proprietary message-based protocol called MINET for call control.

•  NEC's Univerge 7000, which uses both a proprietary stimulus-based call-control protocol called PROTIMS and also supports Session Initiation Protocol-based endpoints via a separate SIP controller.

•  PingTel's SIPxchange, which is based fully and exclusively on standard SIP VoIP call control.

The test bed was configured with two subnets simulating a headquarters and a branch location. The two subnets were interconnected using Cisco routers and Extreme Networks switches. The WAN connection was simulated using a Hurricane IP Network Emulator from PacketStorm Communications. The PacketStorm Emulator let us vary our network environment simulating various impairments including latency, jitter and packet loss.

A mirrored port was configured on the headquarter subnet for the VoIP analysis tools. Five of the seven tools were connected using this port, but the Brix and the Viola products had connections on both sides of our WAN. These two products can generate simulated traffic between their own endpoints to assess the performance of the connecting link.

We used more than eight IP phones to generate real VoIP call traffic between the headquarters and branch subnets. Additionally, some calls were made locally on only the headquarter subnet. Up to four separate VoIP phone calls were placed concurrently, as were conference calls. Before, during and after the calls, the VoIP tools were used to examine the characteristics of the call flows. We used the tools to display call initiation and setup, signaling and any performance statistics relating to the actual VoIP conversation itself.

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