Manual is included.

PRTG Network Monitor is a useful monitoring tool designed to retrieve information from multiple sensors and send notifications to the responsible network administrators. Its purpose is to provide you with real-time information in order to easily identify and solve problems. Network administrators have the permanent need to know what is happening with various devices from their networks. Whether they want to view the bandwidth usage or the availability of a certain resource, this program has the right tools for the job.

http://www.paessler.com/prtg