re. It then discusses a topic not covered much in the literature, namely, how this infrastructure can be used to provide Internet access. It concludes with a qualitative evaluation of the advantages and disadvantages of cable-based Internet access. While ISDN is extensively described in the literature, its use as an Internet access medium is less well-documented. This chapter briefly reviews local telephone network technology, including ISDN and future evolutionary technologies. It concludes with a qualitative evaluation of the advantages and disadvantages of ISDN-based Internet access. 3.1 Cable Technology Residential cable TV networks follow the tree and branch architecture. In each community, a head end is installed to receive satellite and traditional over-the-air broadcast television signals. These signals are then carried to subscriber's homes over coaxial cable that runs from the head end throughout the community Figure 3.1: Coaxial cable tree-and-branch topology To achieve geographical coverage of the community, the cables emanating from the head end are split (or "branched") into multiple cables. When the cable is physically split, a portion of the signal power is split off to send down the branch. The signal content, however, is not split: the same set of TV channels reach every subscriber in the community. The network thus follows a logical bus architecture. With this architecture, all channels reach every subscriber all the time, whether or not the subscriber's TV is on. Just as an ordinary television includes a tuner to select the over-the-air channel the viewer wishes to watch, the subscriber's cable equipment includes a tuner to select among all the channels received over the cable. 3.1.1. Technological evolution The development of fiber-optic transmission technology has led cable network developers to shift from the purely coaxial tree-and-branch architecture to an approach referred to as Hybrid Fiber and Coax(HFC) netwo...
