How does a model-driven telemetry dial-out approach function?

The dial-out model-driven telemetry approach is initiated by the network device, not by the collector. Cisco IOS XE telemetry documentation describes configured subscriptions as dial-out because the publisher, meaning the router or switch, initiates the connection to the configured receiver. After the session is established, the device streams the subscribed YANG-modeled data at the configured cadence or when the configured on-change condition occurs. This model is useful when the telemetry collector is a fixed destination and the network operator wants the device to maintain the outbound session automatically. Option B describes dial-in telemetry, where the collector or subscriber connects to the device and requests the subscription. Option C is also dial-in oriented because the collector initiates the session. Option D is close in wording, but the key design point is that the session is based on an already configured subscription rather than a negotiation process. Reference topics: model-driven telemetry, configured subscriptions, dial-out telemetry, YANG-push, telemetry collectors.