In 1995, the telecommunication infrastructure of the Internet in the United States changed from a publicly supported infrastructure to an evolving infrastructure of cooperating commercial enterprises. The infrastructure now consists of public telephone networks, network access points (NAPs), and Internet service providers (ISPs).
Figure 3.1 U.S. Network Access Points
The new commercial U.S. backbone infrastructure includes the NAPs shown in the preceding figure, which provide interconnection for commercial ISPs. It also includes a Routing Arbiter, which manages routing tables and databases that route the traffic between ISPs across the national backbone.
High-speed digital communications over the Internet infrastructure can provide transmission speeds between 45 and 155 megabits per second. Telecommunications at such speeds is referred to as midband telecommunications. National service providers (NSPs) provide backbone services for the Internet infrastructure using transmission technologies that range from midband telecommunications to fully switched broadband networks based on Asynchronous Transfer Mode (ATM) technology. ATM technology provides transmission speeds up to hundreds of megabits per second.
Demand exists for transmission technologies with even higher bandwidth on the Internet infrastructure. However, the bandwidth problem of primary concern to most administrators of Internet sites is the bandwidth from their sites to the Internet.
Connections to the Internet telecommunications infrastructure are often compared to a highway on-and-off ramp. The speed at which you enter and exit the highway (that is, the speed at which you send and receive data) depends on the road (the technology) that connects you to the Internet, rather than the maximum speed attained on the highway itself. In other words, the WAN bandwidth problems you can reasonably manage are most likely to occur over the connection between your server and your gateway to the Internet.