e city requires inter- office connectivity in order to do business properly. On the other hand, a large multinational with offices and clients in Madrid, San Francisco, Hamburg, and Singapore requires connectivity to ensure that the offices can exchange information on a 24-hour basis. These requirements are satisfied through the proper deployment of wide-area transport technologies. These can be as simple as a dedicated private line circuit or as complex as a virtual installation that relies on ATM for high-quality transport. Dedicated facilities are excellent solutions because they are dedicated. They provide fixed bandwidth that never varies, and guarantee the qual- ity of the transmission service. Because they are dedicated, however, they suffer from two disadvantages: First, they are expensive, and only cost effective when highly utilized. The pricing model for dedicated circuits includes two components: the mileage of the circuit and the bandwidth. The longer the circuit and the faster it is, the more it costs. Second, because they are not switched and are often not redundant because of cost, dedicated facilities pose the potential threat of a prolonged service outage should they fail. Nevertheless, dedicated circuits are popular for certain applications and widely deployed. They include such solutions as T1, which offers 1.544 Mbps of bandwidth; DS3, which offers 44.736 Mbps of bandwidth; and SONET, which offers a wide range of bandwidth from 51.84 Mbps to as much as 40 Gbps. The alternative to a dedicated facility is a switched service, such as frame relay, ATM, or in some cases Gigabit Ethernet. These technologies provide "virtual circuits": Instead of dedicating physical facilities, they dedicate logical timeslots to each customer, who then shares access to physical network resources. In the case of frame relay, the service can provide bandwidth as high as DS3, thus providing an ideal replacement technology for lower-speed dedicated circuits. ATM, on the other hand, operates hand in glove with SONET and 