A node wishes to transmit by initiating a ARB (arbitrate) frame. If no other ports are communicating, the ARB grame is received by the port that transmitted it, the node wins arbitration and begins to send its data.
When more than 1 nodes are arbitrating sumultaneously, the ARB frame with lowest AL_PA wins the arbitration.
Nodes that won arbitratuion can transmit until it finishes. It is not the same as token ring which transmission is limited to a fixed time period. To allow nodes with lower priority to transmit, a port that wins arbitration will set its access variable to 0 which will inhibit arbitration request. This is called fairness algorithm.
Once all talkers are allowed to transmit, the last one will place an IDLE frame to the loop. This casued every nodes to set its access variable back to 1 and the process start over again.
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