The primary purpose of information technology networking and associated protocols is to deliver services such as email, Internet access, and business information system access with high availability and highly responsive performance and zero down-time. Accomplishing this lofty feat requires IT managed services visibility into the health status of every device connected to the network. SNMP (Simple Network Management Protocol) monitors and report the health of networked devices over TCP/IP via both polling mechanisms (SNMP Get) and connection-less notifications (SNMP Traps), and is built-in to most operating systems by default.
SNMP Details
There are three primary versions of SNMP. All three SNMP versions use a hierarchical structure called a MIB (Management Information Base) to manage collections of health status objects that require monitoring. The SNMP protocol also includes a set of default MIBs for monitoring TCP/IP and other items common to all devices that use SNMP. Each device can also support MIBs that specify monitoring of health status items specific to that device and the device specific feature set outside the scope of the default MIBs included with SNMP (such as monitoring the health of a custom web application service).
SNMP version 1 specifies an architecture that includes a Network Management Station (NMS) that runs software configured to poll SNMP devices for health status updates and receive SNMP “trap” messages when major changes in health status occurs. Version 1 also specifies a management agent which runs on each monitored device and answers SNMP polling requests sent from a network management station, monitors and updates device status, and sends traps to the network management station when specific device health measurement parameters, such as temperature or fan speed, are outside of the acceptable range. SNMP version 1 also specifies a security mechanism in which each device participating in SNMP on the network must present a “community string” (which is a type of clear text shared password) to poll or send messages. The more widely used SNMP version 2 and SNMP version 3 improve the protocol’s security mechanism, as discussed in the next post.
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