How is latency measured?

Latency can be measured in one or both directions and is quantified in terms of milliseconds (ms). Latency is measured in two ways: 

  1. One-way latency is the time it takes for a data packet to travel in one direction only and it is generally used to diagnose network problems. 
  2. Two-way latency, also known as ‘round trip latency’, measures the round trip time and this figure is used to calculate MOS (mean opinion scores).


When testing Latency for our customers Spearline performs Two-Way latency tests 

For VoIP calls, a one-way latency of 20 ms is normal; a latency of even 150 ms is barely perceptible and thus acceptable. But anything more than that, the quality and consistency of the call starts to decline. Latency is utterly unacceptable at 300 ms or greater. The International Telecoms Union (ITU) of the United Nations recommends (ITU-T G.114) no more than 150ms latency (one-way) for voice calls. Beyond 150ms (300ms round trip), call quality declines to the point of unacceptable and completely non-productive.