Testing leg latency

In addition to testing throughput, SD-WAN speed tests can also be used to test leg latency. To test leg latency, follow these steps:

1. Determine the download speed of the leg using normal speed testing procedures.

2. Run a TCP download test with a rate limit of 25% of the total bonded speed. For example, if the total speed is 6.0 Mbps, set the TCP download rate limit to 1.5 Mbps.

   

   This ensures that the latency checks during the speed test measure the propagation latency of the leg (the latency seen due to the distance between the CPE and aggregator), not the queueing latency (the latency seen due to packets being placed in large queues).

3. Review the test results. Note the reported latency. The latency chart should be fairly uniform, as in this example below:

   If the latency chart shows a lot of variation, the test result is invalid and the leg should be tested further to determine why the latency varies.