SNMP asks repeatedly and learns late. Telemetry inverts it: the device pushes state streams on schedule (or on event) over gRPC/TCP, encoded in GPB or JSON, shaped by YANG data models — Model-Driven Telemetry.

• Subscription = what data, how often, where to.
• Near real-time, low per-poll overhead, scales where polling collapses.
• Three modes: dial-out periodic, On-Change (event), and once.

It’s the data backbone of SDN controllers and assurance platforms (DNA Center): policy engines need fresh state, not a 5-minute SNMP poll. SNMP won’t die — but “monitoring” in modern designs means streaming.