In every environment, especially in a large one, there are many network critical services that are directly tied on the network infrastructure. Many of them can be monitored by the system administrators, but the core critical services for the whole network are better if they are monitored directly by the network administrator.

Between those critical services, we can find the following:

As it is easy to understand, even if those services are provided from some dedicated server and not network devices, the metrics that you are acquiring from them are fundamental. Those metrics, indeed, play a critical role when you would like to set up a proactive alarm.

An example of a service that can cause a lot of confusion in your network can be the DNS, the DHCP, or even the NTP. In an ideal environment, all those services need to be responsive, and even the response time is crucial; if each one...