A.1 Cable Modems
A.1.5 Cable summary
Many people are tuning into the Internet channel on their TV. Of all the high-speed Internet access solutions, cable TV systems are probably the most talked about. That's partly because they take advantage of existing broadband cable TV networks and partly because they promise to deliver high-speed access at an affordable price.

Internet access via cable is spreading rapidly. However, to reach the mainstream, cable operators face an uphill battle. Like phone companies offering ISDN service, cable operators must gain expertise in data communications if they're going to win and keep customers.

Technical hurdles abound: while satellites are only one-way devices, cable modems can work in both directions if cable operators make their one-way networks into interactive HFC networks. When this is accomplished, the technology could offer the best price/performance combination of any Internet access method to date, delivering close to 10-Mbps speeds at less than $50 per month, which is significantly better than the cost/performance factor of ISDN access.

As discussed, making the cable-to-PC connection requires a cable modem to modulate and demodulate the cable signal into a stream of data. The similarity with analog modems ends there. Cable modems also incorporate a tuner (to separate the data signal from the rest of the broadcast stream); parts from network adapters, bridges, and routers (to connect to multiple computers); network-management software agents (so the cable company can control and monitor its operations); and encryption devices (so your data isn't intercepted or sent someplace else by mistake).

Each cable modem has an Ethernet port that connects to the computer (or network) on one side and a port for the coaxial cable connection on the other. You install an Ethernet adapter in the PC, then connect it to the cable modem Ethernet port with a standard Ethernet cable. As far as your PC is concerned, it's hooked directly to the Internet via an Ethernet cable. There are no phone numbers to dial and no limitations on serial-port throughput (as is the case with ISDN modems). What you do get is high-speed throughput: downlinks vary from 500 Kbps to 30 Mbps, while uplinks can range from 96 Kbps to 10 Mbps.