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

<h2 id="01H8Q61QQ5111KQJK217WXD3QJ">Question</h2><p>How do I use the Twilio network test to troubleshoot agent voice calls? I followed the <a href="https://support.zendesk.com/hc/en-us/articles/10878227300506-Troubleshooting-Issues-with-Zendesk-voice" target="_blank" rel="noopener noreferrer">Zendesk Voice troubleshooting</a> steps and performed the Twilio network test. However, I'm not sure how to read the results.</p><h2 id="h_01KX18AXAJKT55QQ8F1AB9A9RF">Answer</h2><p>Most <strong>Zendesk Voice </strong>(formerly Talk) or <strong>Voice over Internet Protocol</strong> (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.</p><p>Perform the <a href="https://networktest.twilio.com/" target="_blank" rel="noopener noreferrer">Twilio network test</a> 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.</p><p>The Twilio network test is divided into two columns.</p><div style="margin-bottom: 20px; text-align: right;">
<button id="master-toggle" class="btn fw-semibold text-dark" data-action="expand" style="background-color: #DEF991; border: none; outline: none; border-radius: 7px; padding: 10px 20px; font-size: 15px; transition: background-color 0.2s ease;" onmouseover="this.style.backgroundColor='#cbef6d'" onmouseout="this.style.backgroundColor='#DEF991'">
Expand all tabs
</button>
</div>
<script>
document.addEventListener('DOMContentLoaded', function () {
const toggleBtn = document.getElementById('master-toggle');

toggleBtn.addEventListener('click', function () {
const action = this.getAttribute('data-action');
const headers = document.querySelectorAll('.accordion');

headers.forEach(header => {
const isActive = header.classList.contains('active');
const panel = header.nextElementSibling; // Grabs the corresponding .panel container

if (action === 'expand' && !isActive) {
// Open it by simulating a standard click
header.click();
} else if (action === 'collapse' && isActive) {
// Close it by simulating a standard click
header.click();
}
});

// Flip button text and states
if (action === 'expand') {
this.setAttribute('data-action', 'collapse');
this.textContent = 'Collapse all tabs';
} else {
this.setAttribute('data-action', 'expand');
this.textContent = 'Expand all tabs';
}
});
});
</script><div class="accordion"><p>Twilio WebRTC Diagnostics</p></div><div class="panel">
<p>The left column of the page contains general <strong>Pass</strong> or <strong>Fail</strong> diagnostics.</p>
<p><img class="wysiwyg-image-resized" style="width: 500px;" src="https://support.zendesk.com/hc/article_attachments/7856390997018" alt="Twilio WebRTC diagnostics pane displaying pass or fail metrics."></p>
<p>For all the above tests, you must see the green <strong>Pass</strong> message. A red <strong>Fail</strong> message indicates network issues, particularly if you get errors with <strong>UDP</strong>, <strong>TLS</strong>, or <strong>TCP</strong>.</p>
<ul>
<li data-list-item-id="e4ac6bee79e1d9761b707dad7a7d7b852">If an agent works from an office environment, those errors happen because something is blocked. Ensure that your network team follows the <a href="https://support.zendesk.com/hc/en-us/articles/115005468288-Talk-network-requirements" target="_blank" rel="noopener noreferrer">Voice network requirements</a>, opens the necessary ports, and your team adds all necessary IP addresses and domains to your allowlist.</li>
<li data-list-item-id="e1cbb64c7e0571a7ef417f0e4785dea2b">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.</li>
</ul>
<div><div class="note">
<span class="notetitle">Note:</span> You ignore any tests below <strong>Voice: Test call using Opus.</strong>
</div></div>
<h3 id="understand-a-pass-result">Understand a Pass result</h3>
<p>A green <strong>Pass</strong> confirms that your network reached at least one Twilio server for that check. It doesn't confirm that every Twilio IP address is open.</p>
<p>The test connects to one or more servers in the region you're routed to. If at least one is reachable, the check shows <strong>Pass</strong>, even when other addresses in that region's range are blocked. The test also doesn't check every address in the <code>168.86.128.0/18</code> media range, which carries direct call media rather than the STUN/TURN fallback connections.</p>
<div><div class="note">
<span class="notetitle">Note:</span> Treat a <strong>Pass</strong> as a starting point, not as proof that your firewall is fully configured. Allow the full set of IP addresses and ports in the <a href="https://support.zendesk.com/hc/en-us/articles/115005468288-Talk-network-requirements" target="_blank" rel="noopener noreferrer">Voice network requirements</a>, 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.</div></div>
</div><div class="accordion"><p>Log Output</p></div><div class="panel">
<p>The right column of the <a href="https://networktest.twilio.com/" target="_blank" rel="noopener noreferrer">Twilio network test</a> contains the <strong>Log Output</strong>.</p>
<p><img class="wysiwyg-image-resized" style="width: 500px;" src="https://support.zendesk.com/hc/article_attachments/7856435529498" alt="Twilio network test log output details column."></p>
<p>The above screenshot refers to the elements below:</p>
<ul>
<li data-list-item-id="e8163e3f0bba479dc5b614b4584b1a4c2">
<p>Ensure that the logs below appear in green. Red indicates a problem:<br><code>A)</code> <strong>Successfully established a UDP connection to Twilio in ___ ms</strong><br><code>B)</code> <strong>Successfully established a TCP connection to Twilio in ___ ms</strong><br><code>C)</code> <strong>Successfully established a TLS connection to Twilio in ___ ms</strong></p>
<div><div class="note">
<span class="notetitle">Note:</span> The numbers in the test are the highest threshold for Voice.</div></div>
</li>
<li data-list-item-id="ee56617105cff3fbf86f0b80008ff291f">
<p><code>D)</code> Ensure that even though you pass the <strong>bandwidth</strong> test, the results are much higher than the example above. In there, the results represent the lowest threshold in which Voice works reliably.</p>
<div><div class="note">
<span class="notetitle">Note:</span> The numbers in the test are the lowest threshold for Voice.</div></div>
</li>
<li data-list-item-id="eb786cbe96c6f816d8499141901eb8b1f">
<code>E)</code> 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: <code>sydney</code>, <code>sao-paulo</code>, <code>dublin</code>, <code>frankfurt</code>, <code>tokyo</code>, <code>singapore</code>, <code>ashburn</code>, <code>umatilla</code>. For the latest information about regions from Twilio, see <a href="https://www.twilio.com/docs/global-infrastructure/edge-locations/legacy-regions" target="_blank" rel="noopener noreferrer">Legacy Regions</a>.</li>
<li data-list-item-id="ec0b7821e23c4cce011e7be6f7fd35280">
<code>F)</code> The Round Trip Time (<strong>RTT</strong>) is ideally at 150ms or less. The higher the <strong>RTT</strong> value, the poorer quality the call is likely to be.</li>
<li data-list-item-id="e7839e5e2f144645c5b5bea24cb23924b">
<code>G)</code> The <strong>jitter</strong> audit isn't more than 20ms. A high <strong>jitter</strong> causes delays.</li>
<li data-list-item-id="e2cf641dffdd682d10fd446f536032093">
<code>H)</code> <strong>Packet loss</strong> indicates an unstable connection. Even a 1% packet loss causes call issues.</li>
</ul>
</div>