 New York that manages all the credit authorization functions for all the Bob's stores. Location B, the San Francisco area, has five different Bob's stores in different locations. Many customers will want to make purchases using their Bob's credit cards, SO we need to have a communications link back to the New York credit Chapter 1 Telecommunications Technology Fundamentals Location A Front-end Processor Location B Leased Lines Figure 1.12 A network without multiplexers authorization center SO that the proper approvals and validations can be made. Given that it's a sales transaction, the most likely choice of communications link the use of a leased line from each of the locations in San Francisco back to main headquarters in New York. Remember that using leased lines is a very expensive type of network connec- tion. Because this network resource is reserved for one company's usage only, nobody else has access to that bandwidth, and providers can't make use of it in the evenings or on the weekends to carry residential traffic, SO the company pays a pre- mium. Even though it is the most expensive approach to networking, the vast majority of data networking today still takes place using leased lines because they make the network manager feel very much in control of the network's destiny (but don't forget the added incentive for telco salespeople to push these highly profit- able lines). With leased lines, the bandwidth is not affected by sudden shifts of traf- fic elsewhere in the network, the company can apply its own sophisticated network management tools, and the network manager feels a sense of security in knowing who the user communities are at each end of that link. But leased lines have another negative attribute: They are mileage sensitive, so the longer the communi- cations link, the higher the cost. And in a network that doesn't efficiently use that communications link all day long, leased lines can be overkill-and expensive. Plus, beyond the local loop, even leased lines are often bundled together onto a 