ETHERNET

1/1/96

A Local Area Network (LAN) technique developed in the 1980s and very widely used. Devices use interface cards that have unique 10 hex digit addresses. Data is transmitted between devices in packets including addresses and routing addresses. Transmitters attempt to avoid collisions with other transmitters by not transmitting if the network is in use and retransmit after collisions using a "random" delay technique that prevents two transmitters creating a "Mexican Standoff" where their transmissions always collide.

Ethernet can use either hub and spoke or "daisy chained" (actually tapped backbone) wiring with any of four wiring types -- 10Base2 Thinet (50 ohm -- RG58 coaxial cable) -- 10Base5 Ethernet (78 ohm -- RG62 coaxial cable sometimes used with a 15 pin DUI connector) -- 10MHz 10BaseT (Unshielded twisted pair -- 4 wires used] -- 100MHz 100BaseT [Also Unshielded Twisted Pair]. 10-BaseT allows nodes to be 1000 meters from the hub. 100BaseT is limited to 100 meters from the hub. 1000Base T will use a different (larger) packet size so that collision detection can work beyond 10 meters.

10MHz and 100Mhz Ethernet have different rules for cascading hubs. 100MHz wiring is much less tolerant of interference sources such as fluorescent lights.

Note: The original posting date on this article seems to be lost forever.

Return To Index Copyright 1994-2002 by Donald Kenney.