A contention-aware packet-scheduling scheme for slotted optical packet switching (OPS) networks is proposed, which employs edge-traffic shaping to reduce contention, coupled with a modified type of renegotiated service incorporating rate prediction. Queuing and scheduling of traffic is implemented electronically within the edge nodes, shaping user traffic into streams, which have a fixed bit rate only for a short period, which is renegotiated at regular intervals in response to user requirements and network conditions. Via an appropriate protocol, edge nodes gain knowledge of relevant network scheduling and topology information. This is used to schedule user-data packets appropriately, in order to reduce contention. Simulation and analytical results demonstrate that in the core, under typical conditions, packet loss below 10-8 may be obtained, with a load of 0.8 and with core optical-packet switch buffers having only 20-slot capacity. The tradeoffs between parameters affecting such results are investigated, demonstrating clearly that much more modest optical core buffers than previously thought necessary can provide acceptable performance. The performance and scalability of these proposals are investigated and discussed, demonstrating their feasibility.
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