Cable Modem Termination System (CMTS)

Cable modem termination system (CMTS) is a hardware device at the headend of a cable TV network that is used to connect cable subscribers to the Internet Service Provider (ISP). They provide high speed data services like Internet or Voice over Internet Protocol (VoIP) over the cable TV network.


  • CMTS has both radio frequency interfaces and Ethernet interfaces.

  • It transmits and receives user data packets to and from the cable modem attached to the subscriber through HFC network. It then converts them to Internet Protocol packets (IP packets) and routes them to the concerned Internet Service Provider (ISP).

  • Cable modems cannot directly communicate among themselves. So, all data communications should be done via CMTS.

  • CMTSs can act as a bridge or a router in the network.

  • CMTSs can serve different population sizes of cable modems.

  • The quality of service provided by a CMTS to the cable modems is independent of their distances.

  • They provide authorization to users.

  • They can also provide basic filtering against threats and attacks.

Types of Cable Modems

The main two types of CMTS are −

  • Integrated CMTS (I-CMTS) − All the components of I-CMTS are in the same chassis. Thus the RF interface and the IP components are in a single device.

  • Modular CMTS (M-CMTS) − Here, the architecture is broken into two components −

    • the physical downstream component, called the Edge QAM, and

    • IP networking and DOSCIS MAC component, called M-CMTS Core