The holy grail of network and systems management is the ability to predict failures before they hit. Although vendors have a spotty record delivering on promises to foretell system failure, they have made some progress.
Users typically receive notice of network failure via their applications.
Some products also enable service-level settings and compare a range of desktop, network and server performance metrics in real time or according to a set schedule. Networks have been monitored at the network and the server using SNMP and agents. Lightweight agents that sit on users' machines or distributed servers are the newest addition. There are differing opinions about where and how to monitor for best effect. But by and large these approaches are far from perfect.