Figure 4.1 depicts the basic architecture. Management is based on a client-server model. The "manager" is a client process which communicates with managed nodes. These nodes provide information via server processes called "agents". RFC 1470  contains an overview over existing SNMP manager products for different platforms.
Agents can be contacted by multiple managers. The manager contains the management functions and presents management information to the user. It perceives the agent as a virtual data store that is populated with instances of ``managed objects'' (MOs), as shown in Figure 4.2. A managed object is a parameter or an attribute that the agent monitors. Instances of the managed objects are simply the current values of the parameters or attributes.
A manager program sends requests to one or more agents. The agent returns the requested information in response. Each request causes the agent to generate exactly one corresponding response.