Simple Network Management Protocol
Troubleshooting is necessary to recover from problems, but the ultimate goal of the network administrator is to avoid problems. That is also the goal of network management software. The network management software used on TCP/IP networks is based on the Simple Network Management Protocol (SNMP).
SNMP is a client/server protocol. In SNMP terminology it is described as a manager/agent protocol. The agent (the server) runs on the device being managed, which is called the Managed Network Entity. The agent monitors the status of the device and reports that status to the manager.
The manager (the client) runs on the Network Management Station (NMS). The NMS collects information from all of the different devices that are being managed, consolidates it, and presents it to the network administrator. This design places all of the data manipulation tools and most of the human interaction on the NMS. Concentrating the bulk of the work on the manager means that the agent software is small and easy to implement. Correspondingly, most TCP/IP network equipment comes with an SNMP management agent.
SNMP is a request/response protocol. The request and response messages that SNMP sends in the datagrams are called Protocol Data Units (PDU). These message types allow the manager to request management information, and when appropriate, to modify that information. The messages also allow the agent to respond to manager requests and to notify the manager of unusual situations. ...