Explanation
There are two types of subscriptions: periodic and on-change. With periodic subscription, data is streamed out to the destination at the configured interval. It continuously sends data for the lifetime of that subscription.
With on-change, data is published only when a change in the data occurs such as when an interface or OSPF neighbor goes down.https://developer.cisco.com/docs/ios-xe/#!streaming-telemetry-quick-start-guide/streaming-telemetry