 point-to-point local loop is available to most homes and DSL can utilize it to provide access to a residence. It is straightforward to implement because each user has a dedicated point-to-point line. In the cable TV net- works, we have to combine and split data to/from many users. ISDN has a low data rate and it requires network operator investments to the infrastruc- ture to manage the increased load of the exchanges. DSL removes traffic from the switched network and reduces the congestion that Internet users might cause. Since expansion of cellular networks, the importance of subscriber loops for ordinary telephone service has decreased, whereas the demand for wideband Internet access has increased. Subscriber loops provide a high penetration media for wideband Internet access and DSL is a key access tech- nology in the evolution where speech is going more and more wireless, releas- ing the cable network for wideband data services. 6.4.4 Cable TV Networks Another media that is widely available for residential Internet access is a cable TV network. Traditionally it has been one-way broadcast media providing a set of broadcast TV channels to the home. The structure of a traditional cable TV network is shown in Figure 6.22. International and national TV programs are received from a geostationary satellite at a central distribution point, known as the head end (HE). Local programs are added and the set of TV channels is directed to various neighborhoods by fiber optic cables, which terminate into various fiber nodes. Some hundreds of homes nearest to each fiber node receive their programs in analog form from the coaxial cables [6]. The hybrid fiber coaxial cable infrastructure seen in Figure 6.22 was originally designed for unidirectional TV broadcast distribution only. High-speed interactive communications across a cable TV access net- work are made possible by the combination of an upgraded two-way hybrid fiber coaxial cable (HFCC) infrastructure, with a cable modem installed in the home and a cable modem termin