Cable modem termination system

[6][7][8][9][10][11] The channels are later regrouped at the cable headend or distribution hub and serviced by CMTSs and other equipment such as Edge QAMs.

At the other end of the network, an optical node converts the light pulses into RF signals again and sends them through a coaxial cable "trunk".

Traffic from a subscriber's home system goes through the cable modem and out to the Internet in the opposite direction.

Upstream data (data from cable modems to the headend or Internet) is carried in Ethernet frames encapsulated inside DOCSIS frames modulated with QPSK, 16-QAM, 32-QAM, 64-QAM or 128-QAM using TDMA, ATDMA or S-CDMA frequency sharing mechanisms.

A typical CMTS allows a subscriber's computer to obtain an IP address by forwarding DHCP requests to the relevant servers.

Traffic shaping is sometimes performed to prioritize application traffic, perhaps based upon subscribed plan or download usage and also to provide guaranteed Quality of service (QoS) for the cable operator's own PacketCable-based VOIP service.

The second part is the IP networking and DOCSIS MAC Component which is referred to as the M-CMTS Core.

One is the DOCSIS Timing Interface, which provides a reference frequency between the EQAM and M-CMTS Core via a DTI Server.

The DEPI protocol controls the delivery of DOCSIS frames from the M-CMTS Core to the EQAM devices [20] Some of the challenges that entail an M-CMTS platform are increased complexity in RF combining and an increase in the number of failure points.

One of the benefits of an M-CMTS architecture is that it is extremely scalable to larger numbers of downstream channels.

[21] Virtual CCAPs (vCCAPs) or virtual CMTSs (vCMTSs) are implemented on commercial off the shelf x86-based servers with specialized software,[22] and can be used to increase service capacity without purchasing new CMTS/CCAP chassis, or add features to the CMTS/CCAP more quickly.