Northern Telecom Limited

Van P Phung

Rungroj Kositpaiboon

Rungnoj Kositpaiboon

Richard Breault

A method provides reserved bandwidth in a system having dual unidirectional and oppositely oriented buses. The method is intended to enhance the proposed standard, DQDB Metropolitan Area Network. A portion of the bandwidth shared by the stations in accordance with the proposed standard is reserved for distribution to stations on an as required basis. Each station making a request for bandwidth is allocated a part of the reserved bandwidth. Empty isochronous cells are used to provide the reserved bandwidth on the buses.

Method of providing reserved bandwidth in a dual bus system

A method provides effective priority access in a system having dual unidirectional and oppositely oriented buses. The method is intended to enhance the proposed standard, DQDB Metropolitan Area Network. An effectiveness factor K is introduced to enhance the effectiveness of the priority. In one embodiment lower priority CD counters are incremented by K for each higher priority request. A second embodiment also increments lower priority RQ counters. A third embodiment increments the lower priority CD slots only for the highest request received in a given slot. A fourth embodiment also increments lower priority RQ counters. A variation provides a threshold counter for controlling the use of the effectiveness factor.

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Van P Phung