nd Wide Area Network Services conversation. T3 trunks are often used by call centers to access a provider's networks because of their higher call volumes. Headquarters often use T3 service and smaller remote sites use T1 for access to the Internet and Multi-Protocol Label Switching (MPLS) networks. Increasingly, large firms install multiple T3s at their headquarters for their growing bandwidth require- ments. Organizations frequently locate e-mail servers centrally at headquarters SO that the main IT organization is able to manage the server and its security for all sites. This is an example of a hub-and-spoke configuration, in which the headquarters acts as the hub for smaller sites. A Comparison of T1 and T3 Media Requirements T1 is media agnostic. This means that it can operate over any medium, including fiber, copper, and microwave. However, because of its higher speeds, T3 requires fiber, ter- restrial microwave, or satellite-based microwave. The term "terrestrial" denotes that the microwave service is transmitted from land-based towers, not satellites. Telephone companies use T1 and T3 over microwave for hard-to-cable areas such as across rivers and canyons, and cellular providers use microwave as one choice to link together their antennas and data centers with centralized switches. These links referred to as backhaul links. T1 on fiber is more reliable than T1 over copper because fiber is a nonelectric medium. External noise and interference from radio stations does not impair service. Because it is nonelectrical, signals do not fade as quickly as those sent over copper. Thus, less equipment is required to boost signals. In many countries, fiber is commonly in place directly to midsize and large business premises in metropolitan areas. When fiber is brought into a user's premises, the end user must supply the electricity for the equipment on which the fiber terminates. If there is no backup power, customers lose their T1/E1s and E3/T3s when they lose power. T1 and the Inefficiencies of Time-Division Multip