A good first place to start might be the networking vendors themselves. Every vendor has, at minimum, a list of the monitors a given device supports. Given the ubiquity of monitoring protocols such as SNMP, many vendors also have their own recommendation or best practices for monitoring and defining thresholds for their products. Armed with this information, administrators can initially focus on a narrow subset of available monitors and grow as needed. Cisco, for example, recommends not exceeding 60% of CPU utilization on its routers and has published an SNMP message to monitor that statistic.
