Today, the most common local area network implementations are based on the CSMA/CD scheduling scheme. The commercial versions of the CSMA/CD based local area networks are known as Ethernets. The Ethernets provide fair, non-prioritized access to all stations on the network at all traffic loads, use a highly reliable bus topology, provide random access for all stations and employ a simple conflict resolution method of scheduling using the exponential truncated binary backoff method. In a CSMA/CD scheme, when a station needs to transmit, it simply starts sending packets of data. If no conflict is detected, transmission is assumed to be completed. In case of a conflict, all stations in the conflict, independently, calculate the amount of backoff time for scheduling retransmission. Normally, in data communications environments where some level of priority treatment of data or stations is needed, CSMA/CD based networks cannot be used. Therefore, a generalized approach to provide priority in CSMA/CD based networks has long been a subject of interest to researchers.
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