PDF of this tutorialAccess evolution is being driven primarily by strong demands for increasing bandwidth to support a growing variety of user services. Prior to 1994, traffic sent over the Internet was largely text-based information with file transfer and e-mail being among the most popular services. The surge in growth of the Internet during 1995 was in part due to the graphical nature of the World Wide Web (WWW). A significant aspect of this shift is that graphical images generally consist of a large number of bits. To transfer large graphical image files quickly with satisfactory performance meant that higher-speed access technologies were needed than those used to deliver relatively small text files. The WWW also became the base for nurturing other capabilities such as animated graphics, audio, and low-rate video. Each of these capabilities have been pushing the need for increasingly higher-speed access.
Figure 2 is an example of the data rates needed to support various user services and the access rates that have become available over time. (The chart represents average user rates, not peak burst rates on shared media.) The chart shows curves for three segments of the user population: the median, the upper twentieth percentile, and the upper second percentile early adopters. Users are eager for audio and video services, so the challenge is for access systems to meet that demand.
Figure 2. Internet Access Rate Growth
