Allocated and dynamic switch flow control

摘要

A method and apparatus are disclosed for eliminating cell loss in a network switch through the use of flow control of both allocated and dynamic bandwidth. When output buffers in the switch become filled to a predetermined threshold level a feedback message is provided to input buffers to prevent transmission of cells from the input buffers to the output buffers. In order to provide connection and traffic type isolation the buffers are grouped into queues and flow control may be implemented on a per queue basis. The feedback message is a digital signal including an ACCEPT/REJECT message and a NO-OP/XOFF message. An XOFF message can be received while transmitting via allocated bandwith or dynamic bandwidth. In particular, an XOFF (allocated) message may be received with regard to allocated bandwidth and an XOFF (dynamic) message may be received with regard to dynamic bandwidth. An optional tagging technique may be employed to distinguish between requests for dynamic and allocated bandwidth. When ACCEPT is received by the requesting input queue the cell is transferred to the output queue. When REJECT is received by the requesting queue the cell is not transferred. When XOFF (dynamic) is received by the requesting input queue further requests to transfer to that output queue by the requesting input queue using dynamic bandwidth are halted until receipt of an XON message from that output queue. When XOFF (allocated) is received by the requesting input queue further requests to transfer to that output queue by the requesting input queue using allocated bandwidth are halted until receipt of an XON message from that output queue.