Comparative Methods and Issues In Design of Mesh-Restorable STM and ATM Networks

Many sectors of society, business, and industry have become dependent on the availability of communication networks. Today virtually all forms of traffic, whether circuit switched as in telephony, cell-based, or packet-switched, such as in B-ISDN or the Internet, are combined into standard synchronous optical network (SONET) carrier signals for transport on fiber optic transmission systems. A pair of optical fibers operating at the SONET rate of 9.8 Gb/s (called an OC-192) carries the equivalent of 129,000 voice or data circuits. A single cable may contain 48 or more of these fibers. The sheer volume of traffic makes the impact of a cable cut widespread and severe. Such events are, however, surprisingly frequent in practice. They have not only caused widespread congestion effects, but more serious effects such as loss of 911 service, loss of credit card services, and even the shut down of a major air traffic control network (MacDonald, 1994).