Experiments in Line Quality Monitoring

(I.QM) system, ushich has been in regular operation in several IRM locutions. The L Q M system uses a System/7 to gather information about the analog phenomena that occur on telephone data transmission lines. It gathers the information without taking the lines out of service. Described are the ways in which the information fiom the 12QM system is used in daily 0perations;~for example, in one case, use qf the L Q M system contributed to an increase in circuit availability from 82 percent to 99 percent over a one-nzonth period. Data being carried by transmission links in computer networks are often subject to transmission errors resulting from various phenomena occurring on the transmission lines. This paper describes an experimental system for monitoring the quality of data transmission over common carrier leased lines and gives examples of how the information obtained from the system may be used in the daily operations of a computer center. The experiments have been carried out at several locations within IBM. In the following section, we describe the environment and background of our experiments. Interested readers may pursue the general principles of data transmission in, for example, Reference 1. In succeeding sections, we describe our experiments, illustrate the ways in which we use the information, and give some concluding remarks.