Patent ID: 6198724
Filing Date: 2001-03-06
Classification: H04L,H04Q

Abstract:
In a digital communications network for communicating cells wherein virtual channels are established for sequentially transmitting cells, and for each virtual channel there is a subscription rate setting a minimum rate at which cells are transmitted in the virtual channel and a peak cell rate setting a maximum rate at which cells are transmitted in the virtual channel, a method of scheduling cells for transmission comprising the steps of:(a) selecting a next cell for transmission;(b) comparing a current time to a next compliant cell time, the next compliant cell time comprising the earliest time that the next cell is sent in compliance with the peak cell rate of the virtual channel associated with the next cell;(1) if the current time is before the next compliant cell time then selecting a new next cell for transmission;(2) else buffering the next cell and calculating a new next compliant cell time;wherein each virtual channel has a burst credit reflecting a cumulative amount of time that cells for the virtual channel were sent after their respective next compliant cell times, wherein the step of calculating the next compliant cell time comprises, if a minimum time between cells exceeds the difference between a maximum time between cells and the burst credit, then setting the next compliant cell time to a scheduled transmission time of the next cell plus the maximum time between cells and less the burst credit, and otherwise setting the next compliant cell time to the scheduled transmission time of the next cell plus the minimum time between cells, whereby cells are sent as closely in time as possible without exceeding the peak cell rate, missing the subscription rate or exceeding a burst tolerance.