Queue service interval based cell schedular with hierarchical queuing configurations

Abstract

To determine when to service a cell queue in an ATM network, a cell scheduler can use an ideal service interval time. The ideal service interval time of each cell queue is the reciprocal of the bandwidth assigned to that cell queue. An interval based cell scheduler is then initialized by setting a time reference to zero and setting a next service time for each queue to the queue's ideal service interval. The cell scheduler then enters a repeating loop. During each iteration of the loop, the first nonempty cell queue having the smallest next service time value is selected. The selected queue is serviced and its next service time is updated by adding its ideal service interval. The time reference value is also updated. If all the queues are empty, then an idle time slot is allowed to pass. The cell queues may consists of queue groups. For example, several queues can be gathered into a queue group that assigned a single ideal service time. Within this queue group, each queue may be serviced equally using a fair queuing system.