All three technologies permit fast, cheap Internet access. High-speed data communication has been available since the 1960s, first in the form of ISDN lines and then in the form of T1 lines. ISDN, at 128Kb, is better than dial-up access, but not by much. Cable technology uses your existing cable-service provider to provide a link of up to 30Mb to the Internet.
Users then access the Internet at high speeds through the provider.
Now cable companies are upgrading their systems to allow data to be transmitted back to them along the same cable conduit. Accessing the Internet via cable requires the user to upgrade an existing cable box and install a cable modem, which is generally the size of a regular dial-up modem. Generally speaking, only one PC can be attached via the cable line to the cable box. The downside is that cable lines serve not individuals but whole geographic regions. However, Internet-security devices can solve the security problem by admitting only the data that are part of a session initiated by the user.