The first is speed. Second, cable modems can remain online whenever the PC is on, similar to the LANs used in offices. The third factor is competition. Cable modems offer an attractive alternative to using telephone lines to access the Internet. Internet users have the option to shift their service away from the telephone companies' aging copper wire to the relatively newer and more robust cable network.
Cable modems operate over the ordinary cable TV network cables.
Older CATV systems initially used only coaxial cable. Current systems use fiber from the head end to a local optical node, reducing system noise, and coaxial cable from the node to the subscriber. While telephonic approaches dedicate bandwidth to each user, cable networks use a shared bandwidth approach. This approach is generally more economical than ISDN or even DSL service. For example, 500-kbps cable Internet access can provide the same average bandwidth and four times the peak bandwidth of ISDN for less than half the cost.