Every serious VoIP user has at one time or another tested his or her downstream and upstream bandwidth to see if there’s a problem. Sometimes (though rarely at today’s typical broadband speeds), a bottleneck large enough to affect voice conversations is pinpointed through such a test.
But several other internet connectivity factors can have an impact on VoIP quality. Megapath, one of the major independent internet service providers in the U.S., has updated its popular internet speed Speed Test applet (which it acquired when it acquired internet service provider Speakeasy from Best Buy two years ago) to measure them.
For VoIPsters, Megapath’s Speed Test Plus is a very useful web tool to bookmark.
The free service utilizes one of Megapath’s eight U.S. network centers, and automatically attempts to route the tester to the closest (this can be overridden by the user). The centers are in Atlanta, Chicago, Dallas, Los Angeles, New York, San Francisco, Seattle and Washington, D.C.
The user begins the test by choosing whether from a business or residential end point, though after several tests it does not appear that the end result is affected by this choice.
Besides basic download and upload speeds, Megapath’s expanded Speed Test Plus measures three other factors that can affect the quality of a VoIP call. These are:
Packet Loss – The percentage of data packets that do not reach their destination, which causes voice calls to sound choppy;
Latency – The time, in milliseconds, it takes for a data packet to make its way to and from a remote end point. Latency causes periods of silence on VoIP calls, often resulting in the parties talking over one another.
Jitter – Variations, in milliseconds, of latency over time between two end points. When high jitter values exist, voice packets may be transmitted out of order, resulting in echoes and talk-over.
At the end of the tests, which can take a couple of minutes, the user is provided a “Mean Opinion Score (MOS)” that predicts the typical quality of a VoIP call over the tested connection.