Telephone users report a wide variety of problems that they experience, but nearly all of them fall into one of these categories:
Performance issues: no lights/dial tone, unable to make calls, poor voice quality, dropped calls/conferences.
Equipment issues: no lights/dial tone, unable to make calls, unable to access or ping equipment.
Connection/services issues: no lights/dial tone (IP endpoints); unable to make calls (all or part) (T1/E1, tie trunks, data w/ QoS/SLAs, etc.)
Pinpointing the location of the problem as precisely as possible so that any repair actions require minimal effort reduces the repair costs and minimizes the impact on noncorrupted service. Therefore, gathering the pertinent information is essential to the troubleshooting process.