ecalls the joke about military procurement that a B-52 was not an aircraft; it was just a lot of parts flying in close formation. This section examines the optimal design of networks and shows that net- works are more than collections of nodes and links. Because the configuration of a network is the result of optimization, the nodes and links in the final design are selected to achieve the designer's purpose. The parts of the network are necessarily interdependent. 1. Choosing the Network Configuration A network designer chooses a set of nodes N = {1, n} and a set of links , m}, each of which connects a pair of distinct nodes i and j. A network designer chooses the set of nodes and the links between them to maximize profit. For a given set of services, the network designer chooses the network configuration to minimize costs. The network's projected services are chosen to maximize expected Networks in Telecommunications profit, which in turn determines the underlying cost-minimizing network config- uration. Both the nodes and the links of the network affect the costs of delivering the services. The costs of nodes and links reflect the underlying costs of construction, oper- ation, and maintenance. Moreover, the costs of the nodes and links depend on a number of attributes that are critical to delivery of network services. Among these attributes are the following: (1) Capacity of nodes and links; (2) Geographic distance covered by the links, the related features of the terrain such as hills, valleys, and water, and economic and regulatory obstacles; (3) Speed of transmission through nodes and links; (4) Reliability of nodes and links; (5) Durability of capital equipment needed for nodes and links; (6) Relative proportions of construction, operation, and maintenance costs of nodes and links; and (7) Rate of technological obsolescence of nodes and links. All of these factors affect the cost of providing network services through a particular set of nodes and links. A networks should be considered as an integrated whol