ng of hubs and terminals with links of over 1.5 million miles, of which 1.2 million are distribution mains and 300,000 are transmission pipelines (U.S. Department of Transportation 2008, Tables 1-10). The wholesale electric power grid has nodes at which large customers and utilities receive power and genera- tors provide power and links in 2005 consisting of more than 160,000 miles of high-voltage transmission lines, defined as carrying 230 kilovolts or above (North American Electric Reliability Corp. 2007). Communications networks such as the telecommunications network are classic examples of network design. Data networks are constantly evolving, with continual technological change in switching and transmission. The physical network that supports the Internet is composed of dozens of backbone networks connected to each other at exchange points. The backbone networks are privately built and operated by such companies as UUNet (Verizon), Sprint, AT&T, Level 3, and Qwest. In addition to the dozens of backbone providers, there are up to 10,000 regional Internet service providers (ISPs) that provide retail access and over 100,000 networks connected at the regional nodes. ¹ At the nodes of the backbone are high- capacity routers and switches. The nodes of the backbone network include the exchange points between the backbone ISPs and the many connection points of the backbone network with the regional ISPs. The links of the backbone network are high-capacity circuits primarily composed of fiber optic transmission systems. Advances in computer chips that handle optical switching offer the promise of vast increases in the capacity of data transmission systems (Reed 2004). Although the Transportation and Utilities sectors include trucking and ware- housing, it might be instructive also to consider the Wholesale Trade sector as operating wholesale distribution networks, with the Wholesale sector contributing 5.8 percent of GDP. The Wholesale Trade sector includes intermediation activ- ities and management of the distributi