Simple Network Management Protocol (SNMP) is an IETF standard for the transmission of network management information. In the most typical SNMP model, a network management system (NMS) queries a software agent on a remote device about that status of that device. The agent replies with values from the pre-defined management information base (MIB). In an alternative arrangement, agents can be configured to automatically send notifications (called "traps") to the manager in response to select events.
SNMP runs over UDP port 161. SNMP traps run over TCP and UDP ports 162.
See: RFC 1213