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Simple. Your cable modem talks to a Cable Modem Termination System (CMTS), the component that exchanges digital signals with cable modems on a cable network. The CMTS is located at the local office of your cable television company.

The downstream information flows to all connected users, just like an Ethernet network. It's up to the individual network connection to decide whether a particular block of data is intended for it or not.

On the upstream side, information is sent from the user to the CMTS. Other users don't see that data at all. The narrower upstream bandwidth is divided into slices of time, measured in milliseconds, in which users can transmit one "burst" at a time to the Internet. The division by time works well for the very short commands, queries and addresses that form the bulk of most traffic from the consumer to the Internet.

A CMTS will enable as many as 1,000 users to connect to the Internet through a single 6 MHz channel. Since a single channel is capable of 30-40 megabits per second of total throughput, this means that users may see far better performance than is available with standard dial-up modems. The single channel aspect, though, can also lead to one of the issues some users experience with cable modems.

If you are one of the first users to connect to the Internet through a particular cable channel, then you may have nearly the entire bandwidth of the channel available for your use. As new users, especially heavy-access users, are connected to the channel, you will have to share that bandwidth, and may see your performance degrade as a result.

It is possible that, in times of heavy usage with many connected users, performance will be far below the theoretical maximums. The good news is that this particular performance issue can be resolved by the cable company adding a new channel, and splitting the base of users.


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by redxii See Profile edited by big greg See Profile
last modified: 2005-07-31 11:59:04