InformationWeek SMB TechEncyclopedia

A device used to connect a computer to a cable TV service for Internet access. Compared to analog dial-up, cable Internet dramatically increases the bandwidth between the user's computer and the Internet. Download speeds have reached 16 Mbps and beyond, but the connection is asynchronous. In order to prevent users with lower-cost cable access from hosting high-traffic Web servers, the upload speed is approximately 10 times slower. Cable operators also routinely change IP addresses assigned to users to prevent Web hosting (see DDNS).

Connect Via Ethernet
Cable modems connect to the computer via an Ethernet port, which is an always-on connection. Ethernet is a shared medium, and the individual user's speed will vary depending on how many customers are sending or receiving data on that cable segment at the same time. For example, when the kids come home from school around 3pm, many cable users experience a corresponding slowdown. See DOCSIS, cable Internet, Internet appliance and MSN TV.









A Cable Modem System
Internet packets are combined with standard TV programming in a cable modem system. The cable modem termination system (CMTS) is responsible for packet to RF conversion, routing, bridging, filtering and traffic shaping (see CMTS).