1. GetRequest: SNMP manager sends this message to request data from SNMP agent. It is simply used to retrieve data from SNMP agent. In response to this, SNMP agent responds with requested value through response message.

2. GetNextRequest: This message can be sent to discover what data is available on a SNMP agent. The SNMP manager can request for data continuously until no more data is left. In this way, SNMP manager can take knowledge of all the available data on SNMP agent.

3. GetBulkRequest: This message is used to retrieve large data at once by the SNMP manager from SNMP agent. It is introduced in SNMPv2c.

4. SetRequest: It is used by SNMP manager to set the value of an object instance on the SNMP agent.

5. Response: It is a message send from agent upon a request from manager. When sent in response to Get messages, it will contain the data requested. When sent in response to Set message, it will contain the newly set value as confirmation that the value has been set.

6. Trap: These are the message send by the agent without being requested by the manager. It is sent when a fault has occurred.

7. InformRequest: It was introduced in SNMPv2c, used to identify if the trap message has been received by the manager or not. The agents can be configured to set trap continuously until it receives an Inform message. It is same as trap but adds an acknowledgement that trap doesn’t provide.