HP StorageWorks 64 FW 07.00.00/HAFM SW 08.06.00 McDATA E/OS SNMP Support Manua - Page 15

Introduction to SNMP 1 An agent responds to a request by sending a single command, the GetResponse command. This command contains the requested information. A manager changes information (variables) in the agent by sending a single command, the SetRequest command. This command is used to manipulate management data. A trap is used by an agent to report extraordinary events. Refer to Traps and Their Purpose on page 1-5. NMS GetRequest PDU GetResponse PDU Get Values Switch NMS SetRequest PDU SetResponse PDU Set Values Figure 1-1 SNMP Commands and Responses GetNextRequest PDU GetResponse PDU Get Next Values Switch Trap PDU Send Trap Why Variables Exist In a Managed Device Variables are the means by which a switch or director (and other devices) keep track of their performance, control their own performance, and provide access to their performance for network managers. A simple example of a variable's use is to set a port offline and turn the port back on. Some variables just hold values that indicate status (for example error counts). SNMP allows the network managers to have access to some of the same variables for network management. For purposes of the following explanation, an object is a data variable that represents an attribute of a managed device. How SNMP Changes Variables (Objects) in a Managed Device An agent is the entity that interfaces to the actual object being managed (Figure 1-2 on page 1-4). The agent understands the language of SNMP and translates between the manager and the object. Objects may be retrieved and/or modified by the manager, and it is the agent's job to return the requested object's value. Within the agent is at least one, maybe several, collections of definitions SNMP Management 1-3