Abstract: According to the present invention there is provided a scheduling and arbitration process for use in a digital data switching arrangement of the type in which a central switch under the direction of a master control provides the cross-connections between a number of high-bandwidth ports to which are connected on the ingress side of the central switch a number of ingress multiplexers, one for each high-bandwidth input port and on the egress side a number of egress multiplexers, one for each high-bandwidth output port, each ingress multiplexer including a set of N input queues serving N low-bandwidth data sources and a set of M virtual output queues serving M low-bandwidth output data sources, characterized in that the scheduling and arbitration arrangement includes three bandwidth allocation tables, an ingress port table associated with the input queues and having N×M entries each arranged to define the bandwidth for a particular virtual output queue, an egress port table associated with the virtual output que

Abstract: There is disclosed a masking unit (REQMSK) for use in a data packet switching system. The data switching system being of the type having a memoryless cross-back switch (SM) providing cyclic connections under the control of a switch arbiter (SCARB) between ingress routers (IR0, IR1, IR2 and IR3) and egress routers (ER0, ER1, ER2 and ER3). Each of the ingress routers (IR0–IR3) is provided with incoming packet buffering on a virtual output queue basis (VOQ0.0, VOQ0.1, VOQ0.2, and VOQ0.3 for ingress router IR0). Each virtual output queue also produces a connection request signal REQ0.0 to REQ3.3 when the corresponding queue has a data packet in it. The masking unit REQMSK is arranged to randomly mask out correlated connection requests.

Abstract: A data switch is proposed of the type having virtual queue ingress routers interconnected with egress routers by way of a memoryless switching matrix controlled by a control unit which performs an arbitration process to schedule connections across the switch. This scheduling is performed to ensure that data cells which arrive at the ingress routers at unpredictable times are transmitted to the correct egress routers. Each ingress router further includes a queue for time division multiplex traffic, and at times when such traffic exists, the control unit overrides the arbitration process to allow the time division multiplex traffic to be transmitted through the switch.

Abstract: In a data switching system, the ingress and egress ports of a memoryless cross-bar switch are controlled by an arbitration method. The arbitration method uses a three phase process involving (i) a request phase in which each ingress port sends its connection requests to egress ports to which a connection is required, (ii) a grant phase in which each egress port uses a grant pointer to select one of the requests directed to it using a grant pointer, and generates a grant signal, and (iii) an accept phase in which each ingress port selects one of the received grant signals to accept, so defining an ingress to egress port connection across the cross-bar switch. The transition sequences for each of the grant pointers are mutually exclusive, so that any synchronisation of the grant pointers is eliminated on the next arbitration cycle. This is arranged by a setting of the paths taken by request and grant signals.

Abstract: An arbitration process sets the connections to be made between ingress and egress ports of a crossbar switch of a data switching system. A weight parameter is used for each pair of ingress and egress ports. Connection requests are generated indicating ingress ports to be connected to egress ports. A selection is made among conflicting connection requests, to produce a connection proposal for each egress port. Any connection request for which respective weighting parameter is zero is not selected. When one of the connection requests is realised, the weight parameter corresponding to this connection is decreased by one. All the weight parameters for a given egress port are re-set to default values in the case that there are no connection requests for that egress port with non-zero weights.

Abstract: A data switch is proposed of the type having virtual queue ingress routers interconnected with egress routers by way of a memoryless switching matrix controlled by a control unit which performs an arbitration process to schedule connections across the switch. This scheduling is performed to ensure that data cells which arrive at the ingress routers at unpredictable times are transmitted to the correct egress routers. Each ingress router further includes a queue for time division multiplex traffic, and at times when such traffic exists, the control unit overrides the arbitration process to allow the time division multiplex traffic to be transmitted through the switch.

Abstract: In a data switching system, the ingress and egress ports of a memoryless cross-bar switch are controlled by an arbitration method. The arbitration method uses a three phase process involving (i) a request phase in which each ingress port sends its connection requests to egress ports to which a connection is required, (ii) a grant phase in which each egress port uses a grant pointer to select one of the requests directed to it using a grant pointer, and generates a grant signal, and (iii) an accept phase in which each ingress port selects one of the received grant signals to accept, so defining an ingress to egress port connection across the cross-bar switch. The transition sequences for each of the grant pointers are mutually exclusive, so that any synchronisation of the grant pointers is eliminated on the next arbitration cycle. This is arranged by a setting of the paths taken by request and grant signals.

Abstract: An arbitration process sets the connections to be made between ingress and egress ports of a crossbar switch of a data switching system. A weight parameter is used for each pair of ingress and egress ports. Connection requests are generated indicating ingress ports to be connected to egress ports. A selection is made among conflicting connection requests, to produce a connection proposal for each egress port. Any connection request for which respective weighting parameter is zero is not selected. When one of the connection requests is realised, the weight parameter corresponding to this connection is decreased by one. All the weight parameters for a given egress port are re-set to default values in the case that there are no connection requests for that egress port with non-zero weights.

Abstract: There is disclosed a masking unit (REQMSK) for use in a data packet switching system. The data switching system being of the type having a memoryless cross-back switch (SM) providing cyclic connections under the control of a switch arbiter (SCARB) between ingress routers (IR0, IR1, IR2 and IR3) and egress routers (ER0, ER1, ER2 and ER3). Each of the ingress routers (IR0-IR3) is provided with incoming packet buffering on a virtual output queue basis (VOQ0.0, VOQ0.1, VOQ0.2, and VOQ0.3 for ingress router IR0). Each virtual output queue also produces a connection request signal REQ0.0 to REQ3.3 when the corresponding queue has a data packet in it. The masking unit REQMSK is arranged to randomly mask out correlated connection requests.