Local area network with message priority

摘要

A message priority scheme for use in local areas networks (LANS) operating in accordance with carrier sense, multiple access/collision detect (CSMA/CD) bus access protocol. A LAN station having a high priority message to send ignores the carrier sense signal, and thereby obtains immediate bus access. If the high priority message collides with another message already on the bus, both messages are subject to a backoff period. However, the backoff period for a high priority message is guaranteed to be less than that of a low priority message for a certain number of re-transmission attempts. An intermediate priority status is assigned to a message that previously had a high priority status, after a certain number of transmission attempts. The intermediate priority message is deprived of its ability to transmit while ignoring the carrier sense signal, but retains its shorter backoff period.