Introduction to SNMP

SNMP stands for Simple Network Management Protocol, and is a simple protocol that allows devices to expose useful information to other devices. This information can be the CPU fan speed of a computer or the routing table of the router. Almost every network device answers to SNMP requests. SNMP gives Network Managers access to information from nearly every device connected to the Network.

An SNMP network consists of a Network Management System (NMS), Managed Devices, and agents. NMS is software that collects data from the devices, organizes it, and shows it to the end user. The ICONICS SNMP connector functions as a manager in an SNMP scenario. An NMS would monitor or control managed devices that provide SNMP information through the agents. An agent is software that runs on a device (such as a router, printer or PC) and answers to the messages from the NMS. These messages can either be read messages (NMS wants to retrieve data) or write messages (the manager wants to set data). The agent can also send a trap to the NMS. A trap is a notification similar to an alarm, such as "the CPU Temperature is too high!"

Each variable that SNMP can read/write is identified in the form of an Object Identifier (OID). The OID identifies the information in a sequence of numbers. For example, 1.3.6.1.2.1.1.1 is an OID that describes the description (sysdescr) of the device. All of the OIDs for a device make up the MIB (Management Information Base), which represents all the data that the device can expose through SNMP. This information for a device is provided by the manufacturer in the form of a MIB text file. This MIB file acts as a dictionary for the device. The MIB files can be used by the NMS to translate numerical OID strings into human-readable text. For example, 1.3.6.1.2.1.1.1 can be translated as "iso.org.dod.internet.mgmt.mib-2.system.sysdescr", which describes the location for sysdescr (the description of the system) that is inside the folder "system" which is inside "mib-2", and so on.