The reliability of LEC telephone networks

The reliability of local exchange carrier (LEC) networks is described using data obtained from diverse sources. These sources are Bellcore's Outage Performance Monitoring (OPM) process, which is designed to collect information on switch outages lasting two minutes or longer, the Automated Report Management Information System (ARMIS), which supplies reports to the US Federal Communications Commission (FCC) to show industry trends in network reliability, and the US General Accounting Office (GAO), which has recently collected information on each outage lasting at least 15 min and affecting at least 10000 lines during 1990 and 1991. The data show that the availability of network switches is at least 99.9981%, meaning that 99.9981% of the time a customer wants to make an intraoffice call, the switch will be up. The chance that the path between two switches is available is 99.9986%. For interoffice calls involving two switches, the availability of the interoffice network is estimated to be 99.9948%