Patent ID: 6229789
Filing Date: 2001-05-08
Classification: H04L,H04Q

Abstract:
A routing switch for bi-directional transmission of digital signals, said signals including at least some digital signal cells of at least two types, a first type requiring integrity of cell transmission while accepting variable bit rate of transmission, and a second type accepting some loss of cells in transmission, each cell comprising a multi-bit frame with control bits and a data cell, said switch comprising:a plurality of input ports for receiving input cells from a plurality of sources;a plurality of output ports for outputting output cells to a plurality of destinations, each output port having circuitry to identify a plurality of queues of cells awaiting output by that output port;buffer circuitry selectively connectable to both said input and said output ports for holding a plurality of cells of each type after receipt by an input port and prior to output by an output port; andcontrol circuitry including input circuitry for responding to selected control bits forming a path selection identifier to identify which output port or ports is to be used for the cell, said control circuitry further comprising output circuitry to identify a plurality of queues at each output port, said output circuitry being responsive to flow congestion circuitry to indicate congestion for selected types of cell in said buffer circuitry and generate flow control indicators for inclusion in the control bits of an output frame to indicate the state of congestion in said buffer circuitry, said control circuitry being responsive to control bits for each cell (i) to locate any flow control indicator indicating congestion at a connected switch which is the source of said cell (ii) to determine whether each input cell is of said first or second type and which output port or ports is to be used and which queue or queues is to be used for each cell, each queue comprising only cells of a single one of said first or second types and each output port having more than one queue of said cells selected from either of said types whereby each port may be used to output to a connected switch a mixture of cells of both types on a common output path, said control circuitry being operable to inhibit output of cells from any queue at an output port to a destination on a connected switch for which a flow control indicator has indicated congestion for cells of the type forming said queue.