IGT (Integrated Telecom Technology ) : WAC-488-A

ATM Quad Switch Element

The QSE is an advanced communications device enabling the production of high performance ATM systems. The QSE provides connections between 32 switch element interfaces, allowing direct connections to other QSEs or to IgT WAC-487 ATM Quad Routing Tables (QRTs).

Except for multicast connections, the QSE is memoryless. If a Clos- or Reverse Delta-type network is constructed from QSEs, the first one or two switches in the fabric can arbitrarily route Uni cast data from the inputs to the outputs of the QSEs. The remaining QSEs examine a routing tag to determine the destination of the cell. The QSEs send a directed Negative Acknowledgment congestion indication (NACK) signal to the source of the data informing the source if the data got through the switch fabric. If the data did not get through the switch fabric, the NACK signal informs the source where the data was blocked. Since the switch fabric runs faster than the line data rate, the source can retransmit the cells that were blocked in previous trials. The first one or two switches in the fabric can arbitrarily route Uni cast data from the inputs to the outputs of the switch elements, allowing for cells that were blocked in the switch fabric on a particular trial to be rerouted so that blocking on the following trial is minimized. The QSE provides 64 cell buffers for multicast support.

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