Abstract: A computer-implemented method and apparatus for determining the availability of a computer network includes a computer program which receives outage signals that are representative of outages of network devices and network device interfaces, in the event that a particular device has more than one network interface. Also, the program receives online signals on a periodic basis and based on the online signals, determines the average number of online interface-minutes during a subset of a preselected period. Then, the number of outage minutes is divided by the average number of online interface-minutes and substracted from one, to generate an availability signal which can be output as an indication of network availability during the preselected period.