Abstract: A data processing system comprises a first clock domain having a first clock rate, a second clock domain having a second clock rate, and a data path operable to transfer data items from the first clock domain to the second clock domain. The data path comprises a buffer having an input for receiving data items from the first clock domain, and an output port for transmitting data items to the second clock domain in a first-in first-out manner. The buffer has a first pointer for indication of a current first location of the buffer, and a second pointer for indication of a current second location of the buffer. The system further includes a read controller operable to define a read pattern for the buffer, to control output from the buffer in dependence upon such a read pattern, and to adjust such a read pattern in dependence upon a value of such a first pointer for the buffer.

Abstract: A method for controlling data packet routing through a switching element having a first plurality of input ports and a second plurality of output ports, the method comprising the steps of: detecting issuance of a first congestion indicator from an output port of the switching element, the first congestion indicator relating to a first routing request from a first input port of the switching element; allowing reassertion of the first routing request after a first time period; detecting issuance of a second congestion indicator from the output port of the switching element, the second congestion indicator relating to a second routing request from a second input port of the switching element; allowing reassertion of the second routing request after a second time period, wherein the first and second time periods are such that reassertions of the first and second connection requests occur substantially simultaneously. Also provided is a device for controlling such data packet routing.

Abstract: The present invention provides a multi-path network for use in a bridge, switch, router, hub or the like, the multi-path network including a plurality of network ports; a plurality of network elements; and a plurality of network links interconnecting the network elements and the network ports for transporting data packets, each network element including a fault monitor for detecting faults on the network links to which the network element is connected, a plurality of dynamically selectable output ports and output port selection mechanism and each network element being adapted to communicate the existence of a fault back to one or more other network elements via which network elements the faulty network link can be bypassed, and each network element being adapted to update the output port selection mechanism when communication of the existence of a fault is received so that only output ports which ensure the faulty network link is bypassed are dynamically selectable.

Abstract: The invention provides an Ethernet bridge or router comprising a network fabric adapted to provide interconnectivity to a plurality of Ethernet ports, each of the Ethernet ports being adapted to receive and/or transmit Ethernet frames, and wherein the Ethernet bridge or router further comprises an encapsulator connected to receive Ethernet Protocol Data Units from the Ethernet ports, wherein the encapsulator is operable to generate a Fabric Protocol Data Unit from a received Ethernet Protocol Data Unit, the Fabric Protocol Data Unit comprising a header portion, and a payload portion which comprises the Ethernet Protocol Data Unit concerned, and wherein the encapsulator is operable to transform Ethernet destination address information from the Ethernet Protocol Data Unit into a routing definition for the network fabric, and to include this routing definition in the header portion of the Fabric Protocol Data Unit. Also provided is a method of data delivery across a network.

Abstract: The present invention provides a method of limiting the frequency of floods within a data network, the floods arising as a data frame is routed to an unknown destination, the method comprising the steps of: (a) receiving (42) on an ingress port a data frame intended for a destination station and containing a MAC address of that station; (b) checking (50) the destination MAC address with the contents of a MAC table; and thereby (c) determining (50, 54, 58, 62) whether the data frame is to be routed (56), discarded (60, 66) or flooded (52, 64) to all ports except the ingress port; and (d) respectively routing (56), discarding (60, 66) or flooding (52, 64) the data frame to all ports except the ingress port, as determined in Step (c).

Abstract: The present invention provides a multi-path network for use in a bridge, switch, router, hub or the like, comprising a plurality of network ports adapted for connection with one or more devices, each device having a different identifying address data; a plurality of network elements; and a plurality of network links interconnecting the network elements and connecting the network elements to the network ports, wherein the multi-path network further comprises separately addressable memory elements each adapted for storing device address data and the multi-path network is adapted to distribute a plurality of device address data amongst the plurality of memory elements.

Abstract: The present invention relates to a method of managing congestion in a multi-path network, the network having a plurality of network elements arranged in a plurality of switch stages and a plurality of network links interconnecting the network elements, the method comprising the steps of detecting congestion on a network link, the congested network link interconnecting the output port of a first network element with a first input port of a second network element in a subsequent switch stage; identifying an uncongested network link connected to a second input port of said second network element; and directing future data packets on a route across the multi-path network which includes the identified uncongested network link. Also provided is a multi-path network and an Ethernet bridge or router incorporating such a multi-path network.

Abstract: The present invention relates to a method of sorting data packets in a multi- path network having a plurality of ports; a plurality of network links; and a plurality of network elements, each network element having at least first and second separately addressable buffers in communication with a network link and the network links interconnecting the network elements and connecting the network elements to the ports, the method comprising: sorting data packets with respect to their egress port or ports such that at a network element a first set of data packets intended for the same egress port are queued in said first buffer and at least one other data packet intended for an egress port other than the egress port of the first set of data packets is queued separately in said second buffer whereby said at least one other data packet is separated from any congestion associated with the first set of data packets.

Abstract: The present invention provides a method of preserving packet ordering in a multi-path network having a plurality of network elements interconnected by network links wherein for each data packet arriving at an egress port of the multi-path network, a delivery acknowledgement is issued by the egress port and is transmitted across the network following in reverse the path taken by the data packet being acknowledged, and wherein the state of each link in the path taken by the data packet being acknowledged is updated by the acknowledgement.

Abstract: A computer network (1) comprises:—at least two processing nodes each having a processor (4) on which one or more user processes are executed and a respective network interface (2); and a switching network (3) which operatively connects the at least two processing nodes together, each network interface (2) including a command processor and a memory wherein the command processor of said network interface (2) is configured to allocate exclusively to a user process being executed on the processor (4) with which the network interface (2) is associated one or more segments of addressable memory in said network interface memory as a respective one or more command queues The network interface (2) is capable of processing command data at high rates and with low latencies whilst maintaining the security of individual user processes.

Abstract: A computer network (1) comprises:- a plurality of processing nodes, at least two of which each having respective addressable memories and respective network interfaces (2); and a switching network (3) which operatively connects the plurality of processing nodes together, each network interface (2) including a memory management unit (8a) having associated with it a memory in which is stored (a) at least one mapping table for mapping 64 bit virtual addresses to the physical addresses of the addressable memory of the respective processing node; and (b) instructions for applying a compression algorithm to said virtual addresses, the at least one mapping table comprising a plurality of virtual addresses and their associated physical addresses ordered with respect to compressed versions of the 64 bit virtual addresses. The network interface (2) provides visibility across the network of areas of the memory of individual processing nodes in a way which supports full scalability of the network.