Applies To: Cloud-managed Fireboxes, Locally-managed Fireboxes
Your Firebox uses the link monitoring targets you specify for an interface to calculate loss, latency, and jitter. For example, if you configure the External-1 interface to ping 203.0.113.1, the SD-WAN graph shows loss, latency, and jitter for ping communication between External-1 and 203.0.113.1.
To calculate loss, latency, and jitter, the Firebox uses the 100 most recent probe results from link monitoring targets. Probe results are stored in groups of 10. When 10 groups are each filled with 10 probe results, probe results in the oldest group are cleared, and 10 new results are stored. To calculate jitter, the uncorrected standard deviation is used. For detailed information about how jitter is calculated, see How is jitter calculated? in the WatchGuard Knowledge Base.
Establish Baselines
Before you use SD-WAN monitoring data to make decisions about your network, we recommend that you establish baseline values that are specific to your network. To do this, note the average loss, latency, and jitter values calculated for an extended period of time. As a best practice, we recommend that you consider the average values for the last 24 hours. In a stable, healthy network, average values for the last 20 minutes might suffice.
To see data from the last 24 hours or more, you can generate an SD-WAN report. For more information, see SD-WAN Report. To see live status data for the last 20 minutes, see SD-WAN Details.
Each network is different, and some applications are more sensitive to performance issues. For these reasons, you must interpret SD-WAN monitoring data based on your knowledge of your network. For reference, this list shows general interpretations of loss, latency, and jitter values.
| SD-WAN Measure | Good | Performance Impacted | Performance Significantly Impacted | Effectively Down |
|---|---|---|---|---|
| Loss | <1% | 1–2% | 2–5% | >5% |
| Latency | <100ms | 100–200ms | 200–400ms | >400ms |
| Jitter | <20ms | 20–50ms | 50–100ms | >100ms |
Many factors can affect loss, latency, and jitter. For example, the quality of your WAN links and link monitoring targets can affect the reported data.
In the SD-WAN configuration, the default measurement values are:
- Loss — 5%
- Latency — 400 ms
- Jitter—100 ms
For more information about these settings, see Configure SD-WAN and About SD-WAN Methods.