rganized manner. Trunk testing is necessary, because vendors of transmission facilities (common carriers) generally do not test the trunks, SO there is no way to assess their performance. Furthermore, because trunk costs usually dominate telecommunications costs, it is desirable to lease the fewest trunks possible for a required grade of service. Thus, if a trunk is defective, not only is an expensive facility going idle, but service is degraded. 5.6.3 Maintenance and Management Reports The network control center can provide two powerful trouble track- ing mechanisms: an alarm log and trouble tickets. These comput- erized facilities support the network operators and their management by simplifying and assisting in trouble follow-through. The alarm log is generally a computerized form automatically gen- erated each time an alarm is detected by the NCC. Included in the format are the date and time of occurrence, switch identification, message type, status, alarm log entry number, and space for an op- erator entered text area. The operator can be given wide ranging abil- ity to print, display, or update alarm log entries at any time. Analogous to the alarm tracking mechanism, the NCC can provide a computerized trouble ticket log to coordinate and track general troubles. The trouble ticket format can provide time, date and trou- ble ticket number entered by the system. In addition, there can be fields for the operator's name, the site telephone number, an area for trouble descriptions and a status field (open and closed). Both alarm and trouble ticket management summary reports can provide management with visibility, as well as documentation of NETWORK MANAGEMENT 75 problems handled by the staff, and may be used as a gauge of trans- mission performance. 5.7 SPECIALIZED TEST EQUIPMENT External diagnostics or portable data communications testers have decided advantages over central testing and internal diagnostics. First, onsite testers do not burden the network with the cost of build- ing the diagnostics into the netw