tio agent, Envoy, and application</td><td>No</td></tr><tr><td>15021</td><td>HTTP</td><td>Health checks</td><td>No</td></tr><tr><td>15090</td><td>HTTP</td><td>Envoy Prometheus telemetry</td><td>No</td></tr></tbody></table><p>The following ports and protocols are used by the Istio control plane (istiod).</p><table><thead><tr><th>Port</th><th>Protocol</th><th>Description</th><th>Local host only</th></tr></thead><tbody><tr><td>15010</td><td>GRPC</td><td>XDS and CA services (Plaintext)</td><td>No</td></tr><tr><t