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Ethernet
is the leading network technology for local-area networks (LANs). Ethernet
is based on carrier sense multiple access with collision detection (CSMA/CD).
Twisted pair Ethernet uses Category 5 cabling and RJ45
connectors. In a shared Ethernet environment, each data frame is broadcasted
out to all attached stations which are listening. The station that matches
the destination address accepts the data and checks for errors.
An Ethernet workstation can send data only when no other workstation is talking on the network. If the workstaiton transmits data and hears another doing the same, it assumes the transmission collided and data was lost. Each station then waits a random amount of time and tries to send its packet again. As more people try to use the network, the number of collisions, errors, and subsequent retransmissions grows quickly. Networks will slow down at an exponential rate. When more than 50% of the network’s total bandwidth is used, collision rates begin to cause congestion. Files take longer to print, applications take longer to open, and users are forced to wait. At 60% or higher bandwidth usage, the network will slow to a crawl. Standard Ethernet’s bandwidth is 10 Mbps or 10BaseT. Fast Ethernet or 100BaseT, uses CSMA/CD as well but provides 10 times the bandwidth. Gigabit ethernet is here and runs at 1000 Mbps.
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