Using the Delay Test for Call Latency

Objective

The purpose of this test is to identify any latency in a call by measuring the time it takes to count from 1 to 10 utilizing two different parties. This is the test recommended by Twilio. Before using this test, we recommend that you turn on Voice Trace.

Applies To

• Twilio
• Voice

Procedure

The caller calls the callee using the same call flow that reported the issue. The caller should have an additional timer available to measure the duration of the tests (e.g. another phone is the easiest or watch with a timer). When both parties are ready, the caller says 1 and starts the timer at the same time. As soon as the callee hears 1, the callee immediately says 2. As soon as the caller hears 2, the caller immediately says 3. This process goes back and forth until the callee says 10 and at that very moment, the caller stops the timer. The caller then notes the time it took to count from 1 to 10 on the first try. Since it can take some getting used to, it’s recommended to run the test count at least 3 times. Therefore, the next step is to repeat the process 2 times over. At the end of the process, you should have at least 3 test runs. Averaging out the 3 test runs is a good way to see the average latency on the call.

Results

< 4 seconds: Expected for people in the same room

5.5 seconds: Average landline-landline connection

~8 seconds: Average domestic mobile connection (Baseline)

~10 seconds: Average conference call

>10 seconds: Above average latency, can impact the conversation

>12 seconds: Conversation impacted