The community field is typically encoded as a string in a PDU (Protocol Data Unit), specifically in the SNMP (Simple Network Management Protocol) version 1 and 2c messages. This field is used to authenticate and authorize access to network devices and is used by SNMP agents to determine the level of access to resources that a requesting SNMP manager has. When an SNMP manager sends an SNMP message to an agent, it includes the community string as part of the message header. The community string is basically a password that allows the SNMP manager to communicate with the agent and retrieve or modify information about the network device. If the community string is incorrect or not included, the agent will reject the request. In SNMP version 3, additional security features are introduced to provide stronger authentication and encryption of SNMP messages.
