Thus, either the transmission is successful or a new backoff interval
is computed before a retransmit attempt. With each collision and back off, the chance
of a subsequent collision is reduced. In this fashion, the CSMA/CD reduces collisions
and improves transmission efficiency quite dramatically??”an 80 percent improvement
when compared to the prevailing solutions.
18 When we refer to Ethernet, we usually mean the CSMA/CD Ethernet.
19 At the time, existing protocols such as the ALOHA system developed at the University of Hawaii, had
distinctly limited efficiency, mainly due to a higher collision rate.
20 In essence, each computer waits for a different amount of time prior before attempting to retransmit.
Figure 1.4 The original Ethernet schematic
12 Chapter 1
In 1976, Dr. Metcalfe, along with David Boggs, published this research in a landmark
paper entitled, ???Ethernet: Distributed Packet Switching for Local Computer Networks???
in the Communications of the Association for Computing Machinery (ACM) [8]. And on
December 13, 1977, U.S. Patent number 4,063,220, ???Multipoint Data Communications
System with Collision Detection,??? was issued to Xerox Corporation, Dr.
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