and SNMPv3 are now widely supported in new telecom equipment. Several of the prod- ucts mentioned in this book, such as TEMPo by Tenor Networks, and AdventNet's products support many features of SNMPv2 and SNMPv3. 4.2 Object Management Communication between an SNMP manager and a managed device occurs via SNMP in abstract units called Protocol Data Units (PDUs). The communication SNMP manager and a managed device are typically encapsulated in User Datagram Protocol (UDP) packets. There are four main kinds of operation between managers and agents: 1. The manager can perform a get (or read) to obtain information from the agent about an attribute of a managed object. 2. The manager can perform a get-next to do the same for the next object in the tree of objects on the managed device. 3. The manager can perform a set (or write) to set the value of an attribute of a managed object. 4. The agent can send a trap, or asynchronous notification, to the manager telling it about some event on the managed device. SNMP management is achieved by making an SNMP call to the managed device in order to access a managed object. A managed object may be regarded as a value in a database of managed objects in the device. This database is maintained by the device and is populated with parameters that are relevant to the status, performance and configuration of the device (see Figure 4.1). To specify managed objects to the SNMP agent, the SNMP manager or manage- ment application uses a rigorous naming syntax to specify variables. An object name is an object identifier (object ID or OID), which is like a serial number uniquely identifying an object to an SNMP agent. These flaws have been documented by the CERT Coordination Center of the Software Engineering Institute operated by Carnegie Mellon University. 4 Network Management Using SNMP SNMP management application PC running network managed management software objects record database managed object device Figure 4.1 Managed object database in an SNMP enabled device. The SNMP manager must 