Cable Television Laboratories Inc., and its associates have prepared a series of interface specifications known Data over Cable System (DOCSIS) that permit the early definition, design, development and deployment of data-over-cable systems on a uniform, consistent, open, non-proprietary, multi-vendor interoperable basis. This would also back up the cable operators are interested in deploying high-speed data communications systems on cable television systems.

This service allows transparent bi-directional transfer of Internet Protocol (IP) traffic, between the cable system headend and customer locations, over an all-coaxial or hybrid fiber/coax (HFC) cable network.

Cable Modem Termination System (CMTS) and Cable Modem (CM) are the realizations of the transmission path over the cable system at the head end and the customer locations respectively. the interface to the dataover- cable system is called the Cable Modem Termination System - Network-Side Interface (CMTS-NSI) at the head end and as cable-modem-to-customer-premises equipment interface (CMCI) at the customer locations. The operators can transparently transfer IP traffic between these interfaces, which not limited to just datagrams, DHCP, ICMP, and IP Group addressing (broadcast and multicast). ..