| 摘要 |
An ATM scheduler in accord with the invention supports multiple transmission traffic types (e.g. CBR, VBR and ABR) for each of a plurality of virtual path connections (VPCs) on an ATM link. The scheduler maintains one or more scheduling tables defining the hierarchy of traffic types and the scheduling for each type of traffic within each virtual path. In each cell transmit time, one VPC is identified as assigned to the opportunity to transmit in the respective cell transmit time. Each virtual path connection supports at least one type of high priority traffic, such as constant bit rate (CBR) traffic, over a plurality of virtual circuit connections. The scheduler determines if there is a high priority service virtual circuit connection (VCC), from among those associated with the identified VPC, and that has been assigned the current cell time slot. If the scheduling device identifies such a VCC, then the scheduler provides the transmit opportunity for that VCC. For example, if the VCC has CBR service, a cell for that VCC is transmitted over the link in the respective cell transmit time. If the VCC has variable bit rate service, a cell is transmitted if there is in fact a cell ready to send over that VCC. Also, during processing for each cell transmit time, the ATM scheduler accesses a link list. The link list identifies at least one available bit rate (ABR) service type VCC. The link list identified is one associated with the indexed virtual path connection. The ATM scheduler preferably transfers the accessed link list to an ABR work list associated with the indexed VPC. During each respective cell transmit time, if the processing relating to the high priority service(s) did not result in cell transmission in the time slot, the scheduler examines the ABR work list to identify an ABR service type VCC for which there is a cell that is ready to transmit, and the cell for that circuit is transmitted over the link in the respective cell transmit time.
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