Look-ahead reservation-based scheduling for input-output buffered ATM switch

The authors present a decentralised scheduling approach for an input-output buffered ATM switch based on look-ahead reservation that minimises head-of-line blocking. Cells in an input port are queued separately according to their destined output port. To schedule the transmission time of cells in the input buffer, the input port may send requests to output ports to reserve bandwidth and buffer space at most ω cell times in advance. The reservation request carries with it the state information of the input port which allows the output port to compute a conflict-free schedule. Co-ordination among input/output ports are not required. This effectively minimises head-of-line blocking. A simulation study reveals that the performance of the proposed method, in terms of throughput and cell delay, is substantially better than the windowing approach and is close to that of the optimal scheduling method using exhaustive search