Addressing and Correcting VoIP Latency
Latency refers to the time it takes a transmitted audio signal to reach its destination. When a packet travels slowly, due to congestion or poor configuration, the audio signal lags, resulting in delay. To the user, delay sounds like an echo. When troubleshooting latency, understand that three types of VoIP delay occur.
Propagation: Delay resulting from the distance travelled; the further an electronic signal must traverse, the longer its delay. Often, this type of VoIP delay is unnoticeable, unless exasperated by another latency factor. Nevertheless, routing an electronic signal to the shortest path is good practice.
Handling: Known also as serialization, lag arises because of devices on a network. How long a device takes to process and forward a packet determines this factor, though call devices too may play a role.
Queuing: Another facet of serialization, devices may pause transmission when traffic increases or another device experiences problems with connectivity/processing.
Measuring VoIP Delay
Users can monitor latency based on the direction of a transmission—one-way or round-trip. One-way delay adopts our primary definition of latency (see above), whereas round-trip delay includes the time it takes a response packet to find the original source. A user’s threshold for latency is typically 300 milliseconds, though half this number is ideal.
To assess VoIP delay, users can purchase protocol analyzers in either hardware or software form. Such tools monitor specific communication channels and collect various data in real-time to determine wire speed, packet filtering and more. Understandably, protocol analyzers do more than address VoIP delay; they also track jitter and packet loss.
Numerous protocol analyzers are on the market—some commercial, others open-source. Which you choose hinges on your familiarity with networking and audio configuration. Note that handling latency may also originate from your computer, so ensure all audio drivers are up-to-date and support low-latency audio monitoring before shopping around.