eving Data - get, get-next, get-bulk altering Variables - set receiving Unsolicited messages - trap. To perform any basic operation, the OID, instance, hostname and community string must be specified. To specify an object to an SNMP agent, the OID and instance OSS for Telecom Networks must be provided. From the MIB, the user can obtain the OID and to that an instance must be added in order to identify completely the object of interest. The get operation is performed to obtain one or more values from the managed objects. This operation receives a list of all objects under the selected MIB object, or the specified values under a specific object if the MIB node and instance are specified. SNMP get-next is similar to the SNMP get operation, but retrieves the value of the next OID in the tree. This operation is convenient when traversing the MIB tree, and will get the next object after the specified object. Alternatively, it will retrieve the specific object instance, just like get, if an MIB node is specified. With get-next, specifying the instance is optional. The get-bulk operation is used to retrieve voluminous data from a large table. A get-bulk request is executed by providing an OID along with a maximum repeti- tions value and a non-repeaters value. The get-bulk operation is not available in SNMPv1, only in SNMPv2c and v3. The set operation is used to modify variables from an existing value or to provide a value where there is none. However, most network devices have a default value that is maintained by the agent. 4.4 Traps SNMP is equipped with a mechanism called trapping for sending unsolicited man- agement information from a managed device to the NMS. Under predefined condi- tions, such as a power failure or the device having throughput corresponding to 80% of its capacity, the managed device will issue a trap to the manager announcing such a condition. The standard traps are TRAP 0 through TRAP 5. All other traps come under TRAP 6 and these are product-specific or enterprise traps. By "enter- prise" we are