How do I use the Twilio network test to troubleshoot Voice agent calls?

Question

How do I use the Twilio network test to troubleshoot agent voice calls? I followed the Zendesk Voice troubleshooting steps and performed the Twilio network test. However, I'm not sure how to read the results.

Answer

Most Zendesk Voice (formerly Talk) or Voice over Internet Protocol (VoIP) issues come from the network connection speed, stability, and quality. A fast connection isn't enough for real-time voice communication. Dropped packets or an unstable connection also causes issues.

Perform the Twilio network test to understand if your connection works. The test ensures you follow requirements, such as a proper network, open ports, browser support for calls, and wired headsets.

The Twilio network test is divided into two columns.

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Twilio WebRTC Diagnostics

The left column of the page contains general Pass or Fail diagnostics.

For all the above tests, you must see the green Pass message. A red Fail message indicates network issues, particularly if you get errors with UDP, TLS, or TCP.

• If an agent works from an office environment, those errors happen because something is blocked. Ensure that your network team follows the Voice network requirements, opens the necessary ports, and your team adds all necessary IP addresses and domains to your allowlist.
• If the agent uses a home network, ensure they don't have a special setup or a router that blocks ports. Additional investigation of their network is required.

Note: You ignore any tests below Voice: Test call using Opus.

Understand a Pass result

A green Pass confirms that your network reached at least one Twilio server for that check. It doesn't confirm that every Twilio IP address is open.

The test connects to one or more servers in the region you're routed to. If at least one is reachable, the check shows Pass, even when other addresses in that region's range are blocked. The test also doesn't check every address in the 168.86.128.0/18 media range, which carries direct call media rather than the STUN/TURN fallback connections.

Note: Treat a Pass as a starting point, not as proof that your firewall is fully configured. Allow the full set of IP addresses and ports in the Voice network requirements, not only the addresses that pass. A partial set causes dropped calls or one-way audio later if traffic routes to a server you haven't allowed, or when Twilio adds servers.

Log Output

The right column of the Twilio network test contains the Log Output.

The above screenshot refers to the elements below:

• Ensure that the logs below appear in green. Red indicates a problem:
  A) Successfully established a UDP connection to Twilio in ___ ms
  B) Successfully established a TCP connection to Twilio in ___ ms
  C) Successfully established a TLS connection to Twilio in ___ ms

  Note: The numbers in the test are the highest threshold for Voice.

• D) Ensure that even though you pass the bandwidth test, the results are much higher than the example above. In there, the results represent the lowest threshold in which Voice works reliably.

  Note: The numbers in the test are the lowest threshold for Voice.
• E) Check the Twilio client connection and ensure that you're connected to the right endpoint. A virtual private network, or VPN, connects you to the wrong endpoint. For example, if you're in Germany, but the log shows that you're connected to a US endpoint. Connection to the wrong endpoint causes latency. Twilio decides the best route to take, but a VPN hides the agent's actual location or region. The region can be as follows: sydney, sao-paulo, dublin, frankfurt, tokyo, singapore, ashburn, umatilla. For the latest information about regions from Twilio, see Legacy Regions.
• F) The Round Trip Time (RTT) is ideally at 150ms or less. The higher the RTT value, the poorer quality the call is likely to be.
• G) The jitter audit isn't more than 20ms. A high jitter causes delays.
• H) Packet loss indicates an unstable connection. Even a 1% packet loss causes call issues.