Simple Network Management Protocol  (SNMP) is used to collect all information about IP based devices such as printers, switches, routers, servers etc. and manage them on Networks. In briefly SNMP protocol is designed for network management. To control all nodes in the large network is a little though. Therefore SNMP protocol is best way to monitor each node in your large networks.

SNMP are installed one or more administrator computers (Managers), these computers have task of monitoring and managing a group of host or devices on network. Managers get all report information from a SNMP software component (Agent) via SNMP protocol.

SNMP network consists of three keys components

• Managed Device
• Agent (software which runs on managed devices)
• Network Management Station (software which runs on manager).

SNMP use UPD and port number 161 to send requests from agent. When agent receives that request, it will send back to the source port on the manager. The manager will be received notifications on port 162. Transport layer security and Datagram security layer security use the different port, for receiving requests on port 10161 and send back to the source to port 10162.

Principle of SNMP Communication

SNMP protocol data units schema.

References:

https://en.wikipedia.org/wiki/Simple_Network_Management_Protocol

https://technet.microsoft.com/en-us/library/cc776379(v=ws.10).aspx