SNMP Glossary

SNMP Glossary of Key Terms

Agent: A hardware device or software program that reports to an SNMP manager. In network alarm management, an SNMP agent is typically an RTU, but other network devices like switches, routers and hubs can also act as SNMP agents. An SNMP agent can also be a subsection of a larger device, like the SNMP Agent software module in T/MonXM, which mediates T/Mon alarms to SNMP traps.

Community string: An SNMP security password. There are three kinds of community strings:

Read Community: Allows an SNMP manager to issue Get and GetNext messages.

Write Community: Allows an SNMP manager to issue Set messages

Trap Community: Allows an SNMP agent to issue Trap messages.

Compiling: The process of importing a MIB file into an SNMP manager. To compile properly, a MIB file must be formatted in a text file according to the Structure of Management Information (SMI) standard.

COS (Change of State) alarm: A telemetry alarm that is clearly labeled as reporting a change in status from clear to alarm or from alarm to clear.

Event: In SNMP terms, any change of status in a managed object in the network. SNMP equipment can generate traps for many different kinds of events, not all of which are important for telemetry. The ability to filter unimportant events is essential for high-quality SNMP alarm management

Get: An SNMP message issued by a manager that requests the status of a managed object.

GetNext: An SNMP message issued by a manager, used to walk down a range of OIDs. The GetNext request retrieves the value of the managed object one number after the OID listed in the request.

GetResponse: SNMP message issued by an agent in response to a Get, GetNext or Set request from the SNMP manager.

Inform Notification: An SNMP message (supported in some v2c and v3 implementations) that is similar to a trap but requires a confirmation response from the manager. This is more robust than a standard trap and offers better reliability, but it also consumes more network resources.

Internet Protocol (IP): the network layer datagram protocol of the TCP/IP protocol suite. SNMP runs over UDP, which in turn runs over IP.

Managed Objects: Values of network devices that can be read or overwritten by the SNMP manager, like alarm status, control relay status, system uptime, etc. In SNMP terms, every network device is defined in the MIB as a set of managed objects.

Management Information Base (MIB): The MIB is a data structure that describes SNMP network elements as a list of data objects. To monitor SNMP devices, your SNMP manager must compile the MIB file for each equipment type in your network.

Manager: A top-level SNMP master system (hardware or software) serving as the human interface to the SNMP network. The manager can issue Get, GetNext and Set requests to agents and receives GetResponse and Trap messages.

NMS: Network Management Software or Network Management System. Another term for SNMP manager software or hardware.