The Cable Modem Termination System (CMTS) is a component for packet-oriented voice communication in broadband cable networks(BK, CATV). It connects the subscriber-side DOCSIS with the network-side IP network.
Data that the CMTS receives from the cable modem is converted into IP packets and transmitted to the IP routers via the Internet. On the downstream, the IP packets are converted by the CMTS and transmitted to the cable modem. Since several DOCSIS networks are connected to the IP network, the data rate of the cable distribution network is lower than that of the IP network.
The CMTS performs the switching function between the two protocols and regulates access to the IP backbone. It can also regulate data traffic and ensure the agreed quality of service( QoS). To ensure this, the IP network works with Differentiated Services( DiffServ) and the DOCSIS network with the Resource Reservation Protocol( RSVP).