VoIP glossary
What is Latency?
Latency is the one-way delay between someone speaking and the other person hearing them, measured in milliseconds.
Latency explained
Every hop adds latency: encoding the voice, the jitter buffer, the physical distance the packets travel and any transcoding along the route. The ITU guideline is to keep one-way delay under 150 ms for natural conversation. Above roughly 300 ms people start talking over each other.
Distance matters but routing matters more. A call from Singapore to London that travels via the US can add 100 ms compared with a direct path. When choosing routes for long-distance destinations, ask where traffic hands off to the local network.
Example
A call between Sydney and Frankfurt measures 165 ms one way. It is usable, but the agents notice the slight pause before replies.
Put it into practice
Prepaid SIP trunks and wholesale routes from $200. Ask sales for rates or the NOC for a technical answer.