Ethernets

computers to laser printers. Ethernet employs Carrier Sense Multiple Access/ Ethernet is probably the best known example of a bus structured LAN. It consists of one 0r more segments of coaxial cable to which devices are known as transceivers. Each device requiring a connection to the network is joined through a transceiver which monitors network traffic and a controller which provides the interface between the equipment and the network A connected device is able to send data if its controller finds that there is no other transmission in progress. The controller circuit is, of course designed to guard against mishap should two or more devices believe the highway, or data channel, is free. Each transceiver contains a collision detect circuit which continuously monitors activity on the highway. If a collision is detected, the appropriate controllers are notified and the transmission ceases at that point. After random delays, the controllers involved look again to see if the channel is clear and retransmit the same data (starting at the beginning again). Destination controllers are also informed when any collision occurs and thus are alerted to ignore any corrupt packets which may arrive. In reality, because of the very high data transfer rate and well controlled mode of operation, there is rarely a need to retransmit packets.

The first network access system, called Ethernet, was developed by Xerox in the 1970s to link Collision Detection (CSMA/CD).The three most popular implementations of Ethernet are called 10Base-5, 10Base-2,10Base-T.

The number 10 indicates the speed in megahertz,” Base” indicates that it’s based on Ethernet, and the last number indicates the cable used to connect the node. Ethernet can use any of the network architectures, star, bus, or ring. 10Base-5 and 10Base-2 use bus architecture and 10Base-T use a star architecture.

The latest version, Gigabit Ethernet, delivers data at gigabit speeds making it possible to deliver multimedia applications over the network