SNMP - Simple Network Management Protocol
Simple Network Management Protocol is the most popular network management & monitoring protocol that works in an IP network. It collect information from an array of networking devices mainly the router, switch, hub, servers etc. The protocol works independent of the vendor, as the protocol is implemented by most of the world's popular manufacturer including Cisco, Microsoft, IBM, HP and many more.
The protocol is most commonly used by the "network administrators" to know the status of different network and information devices monitored by them. It may be used to query the network status, bandwidth status, traffic, cpu usage or any other system or network information.
This application layer protocol works by sending messages to different parts of a network. These messages are known as protocol data units (PDUs). These PDUs are received by the network-management module, we call "agents", found on the networking devices. These devices store system information about themselves in a repository known as Management Information Bases (MIBs). This data is sent as a reply to the manager (SNMP requester).