| 摘要 |
A switching device for switching ATM cells from a plurality of network input links to a plurality of network output links comprises a plurality of ports containing line interfaces and input and output buffers, a hardware switch controller, a microprocessor, and memory for storing routing tables and system software. All these elements are interconnected via a processor bus, and additionally, the ports are interconnected by a separate switching bus. The switch controller employs hash-based routing table indexing to route cells from selected input ports to appropriate output ports according to the cells' header information. Switch requests generated by incoming cells are arbitrated using a token bus allocation scheme. The majority of cells are switched almost entirely in hardware, but the microprocessor can assume control of the switching architecture to resolve exception conditions and to perform special processing on selected virtual circuits. Two output buffers per port are provided; one for high-priority cell, another for lower priority cells. Additionally, a common overflow buffer is provided to temporarily store cells intended for output buffers momentarily full.
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