How to Measure Latency
Latency is measured in milliseconds (ms), which are thousandths of a second. A latency of 20 ms is normal for VoIP calls; a latency of 150 ms is barely noticeable and therefore acceptable. Any higher than that, however, and quality starts to diminish. At 300 ms or higher, latency becomes unacceptable. Latency is measured in two ways:
One-direction latency is the time a packet takes to travel one way—from the source to the destination.Round-trip latency is the time a packet takes to travel to and from the destination—back to the source. (The same packet doesn’t travel back, but an acknowledgment does.)
Effects of Latency on Voice Calls
The negative effects of latency on call quality include:
Slow and interrupted phone conversations.Overlapping noises, with one speaker interrupting the other.Echo.Disturbed synchronization between voice and other data types, especially during video conferencing.
Latency Causes and Fixes
Eradicating latency is difficult and involves several factors, many of which are beyond your control. For instance, you do not choose which codecs your service provider uses. Here are the factors that cause VoIP latency and what, if anything, can be done to fix it.
