Cable television companies have a well-established and wide-reaching infrastructure for television programming. This infrastructure might contain both coaxial and fiber-optic cabling. Such an infrastructure is called a hybrid fiber-coax (HFC) distribution network. These networks can designate specific frequency ranges for upstream and downstream data transmission. The device located in a residence (or a business) that can receive and transmit in those data frequency ranges is known as a cable modem.
The frequency ranges typically allocated for upstream and downstream data are 5 MHz to 42 MHz upstream and 50 MHz to 860 MHz downstream.
Although the theoretical maximum upstream/downstream bandwidth limits are greater (and dependent on the HFC distribution network in use), most upstream speeds are limited to 2 Mbps, with downstream speeds limited to 10 Mbps. As HFC distribution networks continue to evolve, greater bandwidth capacities become available.
The frequencies dedicated to data transmission are specified by a Data-Over-Cable Service Interface Specification (DOCSIS) version. Although DOCSIS is an international standard, European countries use their own set of frequency ranges, their own standard known as Euro-DOCSIS.