FDDI protocols optimized for real time and packet data transmission

The high performance protocol of the fiber data distributed interface-hybrid ring control (FDDI-HRC) is discussed to show its strengths and weakness with regard to the task of concurrently meeting the needs of real-time and packet data applications. The random allocation and de-allocation of isochronous bandwidth (the bandwidth allocated to real-time applications) in an FDDI-HRC system could cause the packet data traffic to be constantly interrupted. Changing the allowable packet data bandwidth affects network performance and alters the balance between delay and throughput established on the asynchronous channel with the selection of TTRT (target token rotation time). Therefore, claim token bidding cycles can be initiated under heavy load conditions to reselect TTRT. It is shown that a new claim token bidding cycle might not always be required, and a method to adjust TTRT to the changing bandwidth on the asynchronous channel without the claim token bidding cycle is provided