Cable Modem Termination System
The CMTS takes the traffic coming in from a group of customers on a single channel and routes it to an Internet service provider (ISP) for connection to the Internet. At the head-end, the cable providers will have, or lease space for a third-party ISP to have, servers for accounting and logging, Dynamic Host Configuration Protocol (DHCP) for assigning and administering the IP addresses of all the cable system's users, and control servers for a protocol called CableLabs Certified Cable Modems -- formerly Data Over Cable Service Interface Specifications (DOCSIS), the major standard used by U.S. cable systems in providing Internet access to users.
Another benefit of the cable modem for Internet access is that, its performance doesn't depend on distance from the central cable office. A digital CATV system is designed to provide digital signals at a particular quality to customer households. On the upstream side, the burst modulator in cable modems is programmed with the distance from the head-end, and provides the proper signal strength for accurate transmission.
XGCM
This module is responsible for providing MGCP embedded client functionality. It parses and processes each message received from an MGCP call agent. It reports detected events to the call agent, generates signals requested by the call agent, reports detected DTMF digits, and sets up connections requested by the call agent. This module is also responsible for forwarding audio packets received from the DSP to packet network interface and forwarding audio packets received from the packet network interface to the DSP.
Introduction
Voice (and fax) service over cable networks is known as cable-based Internet Protocol (IP) telephony. Cable based IP telephony holds the promise of simplified and consolidated communication services provided by a single carrier at a lower cost than consumers currently to pay to separate Internet, television and telephony service providers. Cable operators have already worked through the technical challenges of providing Internet service and optimizing the existing bandwidth in their cable plants to deliver high speed Internet access. Now, cable operators have turned their efforts to the delivery of integrated Internet and voice service using that same cable spectrum.
Putting both upstream and downstream data on the cable television system requires two types of equipment: a cable modem on the customer end and a cable modem termination system (CMTS) at the cable provider's end. Between these two types of equipment, all the computer networking, security and management of Internet access over cable television is put into place.
Tuner
The tuner connects to the cable outlet, sometimes with the addition of a splitter that separates the Internet data channel from normal CATV programming. Since the Internet data comes through an otherwise unused cable channel, the tuner simply receives the modulated digital signal and passes it to the demodulator.
Fax Software
This software performs a fax relay function by demodulating PCM data, extracting the relevant information, and packing the fax-line scan data into frames for transmission.
Unsolicited Grant Service(UGS)
Cable networks are asymmetric, i.e., the downstream data received is streaming while the upstream data transmitted is either transmitted on a collision time fragment or must get a time slot or grant. Because requesting a grant can cause significant delay, UGS ensures that cable modems will be contacted at regular intervals without having to make separate requests. The concatenation process mentioned earlier can lighten UGS requirements and increase the efficient bandwidth.
Abstract
Voice (and fax) service over cable networks is known as cable-based Internet Protocol (IP) telephony. Cable based IP telephony holds the promise of simplified and consolidated communication services provided by a single carrier at a lower cost than consumers currently to pay to separate Internet, television and telephony service providers.
Conclusion
With the merging of telecom carriers, cable operators, and Internet service providers (ISPs), most experts agree that convergence is not merely a trend but an inevitability. The potential cost savings, consolidated billing, streamlined network management, and overall convenience are too compelling for service providers and customers to ignore.
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