I recently listen to Greg Ferro's podcast on the topic - "Considering KPIs For Network Operations" and it really triggered me to think extensively on this topic. So I have spent several hours researching and think about how we measure network availability and performance, and what are the most important metrics that we measure.
Usually at first people associate network metrics with availability. So lets look at availability as KPI
Measuring network availability is not as straightforward as one might think. It is easy to measure the availability of one component of the network like a leased line for example. You have a monitoring system that constantly looking at the status of the line and reports any downtime. But one leased line down usually doesn't affect the services using the network.