Xyratex Technology Limited

Virtensys Limited

Paul Howarth

Ian David Johnson

Marek Piekarski

Finbar Naven

Yves Constantin Tchapda

Michael Patrick Robert Collins

Simon William Farrow

A switching device comprising a plurality of ingress ports and a plurality of egress ports. The switching device is arranged to receive data packets through the ingress ports and to forward received data packets to respective ones of the egress ports. The switching device further comprises an ingress module for each of the ingress ports, each ingress module being arranged to receive data packets from a respective single one of the ingress ports and to store the received data packets in one of a plurality of data structures provided by the ingress module, each ingress module being further configured to select a data packet from one of the plurality of data structures, and to request permission to transmit the selected data packet to an egress port. The switching device also comprises at least one egress module arranged to receive a plurality of requests for permission to transmit data packets through a particular egress port, the request being generated by the plurality of ingress modules, and to select one of the plurality of requests.

Switching method

A data switch for handling packets of information; the switch includes input traffic managers, ingress routers, a memoryless cyclic switch fabric, egress routers and output traffic managers all acting under the control of a switch controller. Each ingress router includes a set of virtual output buffers one for each output traffic manager and each message priority. Each data packet or cell as it arrives is examined to identify the output traffic manager address and its message priority. The switch controller uses a first arbitration and selection process to schedule the passage of the next cell across the switch fabric which the ingress router uses a second arbitration and selection process to select the appropriate virtual output queue for use in the switch fabric transfer.

Method of transmitting information through data switching apparatus and apparatus therefor

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.

Data switch and a method for controlling the data switch

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.

Method and arbitration unit for digital switch

A scheduling means for data switching apparatus includes a plurality of input ports and a plurality of output ports, the scheduling means capable of processing a plurality of interconnection requests, each requesting interconnection between a sub-set of the input ports and a sub-set of respective the output ports, and each request having a respective priority level which is one of a predetermined number of priority levels. The scheduling means includes determination means for determining a first set of requests selected from the plurality of requests, according to the respective priority levels; a first pipeline stage for receiving only the first set of requests am satisfying at least one of the first set of requests; a priority mixer for determining a further set of requests independently of the priority levels, the further set including requests of the first set which were not satisfied and requests included in the plurality of requests which were not part of the first set and which are of any of the priority levels, and an additional pipeline stage for identifying requests in the further set which can be satisfied, and for satisfying the identified requests.

Scheduling means for data switching apparatus

A data packet switching system having a central controller and a number of peripheral controllers each incorporating at least one queue for storing packets of information received from a peripheral data packet source. Each queue in each peripheral controller includes a queue size detection logic adapted to communicate to the central controller the approximate state of the size of the corresponding queue. The scale for the approximate state being arranged to be empty, nearly empty, active, busy, very busy, nearly full and full.

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Sale, United Kingdom

Paul Howarth