HP Network Direr Software Products manual Service Polling, Snmp Trap Receipt

278CHAPTER 7: MONITORING THE NETWORK

Service Polling

3Com Network Director provides support for monitoring the status of various services that may be provided by servers in your network, including such services as DNS, FTP, POP3 and SMTP mail.3Com Network Director monitors a service by connecting to and sending a request to the service on a regular basis.The response received, or the lack of any response, is used by 3Com Network Director to update the state of the monitor.

Depending upon the service being monitored, the monitor may be able to use the response to determine more than just the responsiveness of the service i.e. how quickly the response is received.Some services, such as DNS, support status requests to which they respond with details of the internal status of the service. 3Com Network Director will use these status requests when they are available to provide more detailed information about the service status.

SNMP Trap Receipt

Network infrastructure devices that maintain statistics about their operation and allow access to this information via SNMP MIBs often also support the concept of SNMP traps.SNMP traps are unsolicited messages sent out by the devices when the data stored in the SNMP MIB indicates that the device is in certain states.These may indicate simple state changes such as a port going up or down, or may indicate more complex state changes, such as the received packet rate reaching a particular level.

Devices that support SNMP traps are known as trap sources.In order for another device to receive the SNMP traps from a trap source it must register with the trap source as a trap destination.When a trap source enters a state for which it will generate an SNMP trap it sends the trap to all registered trap destinations.

SNMP trap receipt is the only passive monitoring technique used by 3Com Network Director. 3Com Network Director optionally registers the PC it is running on as a trap destination with all monitored network infrastructure devices that support SNMP traps. When 3Com Network Director receives an SNMP trap it determines whether or not it has a monitor associated with the trap type.If it does then the trap is used to update the state of the monitor.