er a network of interconnected networks. The FCC has found it useful to divide the networks that compose the Internet into three types. Backbone providers provide high-speed, long distance connections between a small number of interconnection points. Middle-mile providers provide regional distribution functions, carrying the traffic from the limited number of interconnection points served by backbone providers to the local distribution facilities maintained by last-mile providers in individual cities (which in the case of DSL are usually called "central offices" and in the case of cable modem systems are usually called "headends"). 3 Last-mile providers convey the traffic from these local distribution facilities to the premises of end 2 Originally, backbones only interconnected at the four public network access points (NAPs) cre- ated by the National Science Foundation (located in San Francisco, Chicago, New York, and Washington, DC) and the Commercial Internet Exchange maintained in Santa Clara, California (Kende 2000). The NAPs have since been privatized, and backbone providers have also created a number of other public interconnection points, where any carrier can exchange traffic. In addi- tion, backbone providers have begun to exchange traffic directly through private interconnection points (Yoo 2004b). Depending on the context, the FCC sometimes replaces the term "backbone providers" with the term "long haul communications transport facilities" to make clear that it is referring to high-speed fiber transport used for voice as well as data communications (FCC 2002a). Under broadband, middle-mile and last-mile provision are often vertically integrated. This is because real efficiencies often result from such integration (Yoo 2004b). Networks in Telecommunications Server Middle Backbone Middle Server Backbone Backbone Middle Middle Server Figure 12.1. The basic architecture of the Internet. users. The FCC has analogized this to a road system. Backbones represent inter- state highways, which convey traffic at h