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Network bandwidth diagnostic

Network bandwidth diagnostic allows administrators to test network bandwidth between specific Agents and troubleshoot performance issues.

To test network connection speed between two Agents:

  1. In the Management Console, select Settings > Diagnostic.

    Management Console Settings

  2. Choose two Agents between which you want to test the connection bandwidth.

    Note

    Both Agents must remain online during the test.

  3. Select the connection protocol you want to use.

    Note

    • The protocol configuration in the Agent’s profile does not affect the network test.
    • The WAN optimization feature must be enabled in the license for at least one Agent to run the test with the ZGT protocol. Otherwise, the test will fail.

  4. Click Start Test.

    Diagnostic Network

Network diagnostic details

  • Agents use their standard peer discovery mechanisms. Discovery through known hosts only does not work.
  • Files are not hashed during the speed test. On real data, if hashing is enabled in the Job or Agent profile, synchronization speed may differ from the test results.
  • During the test, Agents send random 128 KB packets for 10 seconds. The resulting speed samples indicate the available bandwidth between the two peers. This reflects the speed at which Agents can transfer data.
  • Bandwidth scheduler rules are not applied during the test. However, license-based speed limits are enforced, which is indicated with the Agent’s bandwidth is limited by the license package warning.
  • The test runs once. To start a new test, close the results dialog and click Start Test again.

Diagnostic Network Results

The following information is a available in the network test results:

  • SSL encryption speed on uploading side.
  • rtt - Packet round-trip time, reported for both sides.
  • spd3Diff - Actual send speed difference compared to the speed limit. A persistent non‑zero percentage indicates underperformance on the uploading side. This metric is intended for troubleshooting by the Resilio Support team.
  • ctrl3Drop - Lost packets.
  • snd retr - Percentage of packets retransmitted due to loss or timeout (for example, high RTT deviation).
  • rcv drop - Percentage of packets dropped on the downloading side due to window limitations (indicates lost acknowledgments or slow processing on the receiver side).