Service Level Indicators (SLI) are specific metrics, such as up-time, response time, or error rates. To measure how well a service is running, we compare SLIs to Service Level Objectives (SLOs) that describe requirements for the service, such as 99.9% up-time. Finally, there are Service Level Agreements (SLA), which are formal promises that outline expected levels of service.
Network monitoring
SNMP is the Simple Network Management Protocol, which allows devices to report performance data using a structure called Management Information Base (MIB).
It is a centralised system where each device will send data to a server. Each item in the MIB is assigned an Object Identifier (OID) which can be used to locate specific information.
SNMP also has Traps, which are automatic alerts that can be triggered by specific events.