Defeating Telecommunication System Fault-Tolerant Designs

Telecommunications carriers suffer large-scale outages that impact hundreds of thousands of subscribers by the improper deployment or operation of otherwise faulttolerant designs. This paper gives examples of such outages in telecommunications signaling, transmission, and power systems. In spite of seven years industry tracking of largescale outages at the national level, the survivability of the public telephone network has not improved, as the frequency of outages is not decreasing. This surprising phenomenon is all the more remarkable in that well-known outage scenarios continue which defeat otherwise fault tolerant systems. Averting such survivability deficits requires less focus on fault-tolerant designs and more focus on organizations and people. It remains to be seen if local access competition will remedy these survivability problems, as voice, video, and data service offerings are bundled by carriers.