Monitoring devices (commonly called "probes" in this context) contain RMON software agents that collect information and analyze packets.
While both agent configuration and data collection use SNMP, RMON is designed to operate differently than other SNMP-based systems: In short, RMON is designed for "flow-based" monitoring, while SNMP is often used for "device-based" management.
RMON is similar to other flow-based monitoring technologies such as NetFlow and SFlow because the data collected deals mainly with traffic patterns rather than the status of individual devices.
One disadvantage of this system is that remote devices shoulder more of the management burden, and require more resources to do so.
A minimal RMON agent implementation could support only statistics, history, alarm, and event.