Roke Manor Research Limited

Andrew Reeve

Simon Paul Davis

Neil Duxbury

A networked probe system for a communications network () comprising at least one user device and at least one network device, comprises a plurality of probes (). A probe () is provided in each path between the or each user device and the or each network device. Each probe () stores one or more parameters of interest. The probes () monitor communication from the user device for a subset of the communication satisfying the one or more parameters. On determining the presence of the one or more parameters in the subset of the communication, the probe () provides a notification to all other probes in the network ().

Networked probe system

A network resilient to at least two points of failure comprises a plurality of nodes. A first path between a source node and a destination node is determined and a second path between a source node and a destination node is determined. The first and second paths are node-disjoint.

Resilient network

A router device has a plurality of ingress line interface cards (LICs), a plurality of egress LIC's, a backplane and a controller. Transmission of signals from the ingress LICs to the controller, and from the controller to each of the ingress and egress LICs takes place across the backplane. Each ingress LIC is provided with a dedicated timeslot in which it can send information to the controller via connection. Information is sent in a slice within the dedicated timeslot and each egress LIC ignores data sent by a given ingress LIC within the timeslot assigned to said ingress LIC. A similar system is used for transmission of communications from the controller to the LICs. It is thus possible to avoid provision of additional, dedicated communications paths between the LICs (ingress and egress) and the controller.

Packet switches

In a method for cell level scheduling for handling multicast traffic in routing devices, such as cross-bar switches having, a plurality of ingress line interface cards (LICs), a plurality of egress LICs, a cross-bar and a controller, multicast and unicast data traffic passes from the ingress LICs via the cross-bar to the egress LICs. A given multicast data packet is sent from a given ingress LIC to a predetermined set of egress LICs known as the fanout of the given packet. Each ingress LIC has an associated rate of send opportunities. The method allows multicast send opportunities to be spread as evenly as possible over cell periods, by invoking a conventional unicast scheduling scheme when one or more multicast send opportunities are present. The schedule is filled out with the fanouts of multicast packets in accordance with the send priority associated with the respective ingress LICs upon which each of the respective multicast packets is queued.

Packet switching

The invention relates to a switching device () having a plurality of line interface cards (LICs) (), a plurality of egress LICs (), a cross-bar () and a management card (). The switching device () routes fixed sized cells of data across the cross-bar (). The cells comprise fragments of variable length data packets. Each ingress LIC () is associated with a respective schedule or timetable () governing the transmission of cells by the ingress LIC. Similarly, each egress LIC () is also associated with a respective schedule or timetable () governing the reception of cells by said egress LIC. The schedules are in the form of a table whose entries are the identities of transmission queues corresponding to a respective egress LIC identification number (for ingress LICs) and ingress LICs from which to receive (egress LICs). Each ingress and egress LIC maintains a pointer into its associated schedule. At each cell transmit time, each ingress LIC transmits a cell from the queue identified by the pointer and each egress LIC will receive the cell from the ingress LIC identified in the entry referenced by the pointer. The pointers then move to the next location. Each schedule is circular in the sense that when moving the pointer from the last entry, its next position is the first entry.

Switching devices

Described herein is a method for reassembling variable length packets from fixed length cells. When a variable length packet, for example, an Internet Protocol (IP) packet, is transmitted between routers over a link which transmits data as fixed length cells, for example, an asynchronous transfer mode (ATM) link, the packet must be segmented into compatible fixed length cells. The receiving router must reassemble the original packet from the cells as they arrive. A packet buffer free pool () is provided which is maintained as a linked list, known as a 'free list', and which comprises a plurality of buffer elements (). When a first cell for a given packet arrives, a buffer element () is taken from the head of the free list and allocated to that packet. The packet data from the first and subsequent cells is copied into the allocated buffer element and each time the buffer element is moved to the end of the free list. Upon the arrival of the last cell for the given packet, the complete packet is processed. Failed reassemblies are automatically abandoned as the buffer element is reused when it reaches the head of the free list. This technique is relevant to protection against 'denial of service' attacks upon computer networks.

Growing community of inventors

Winchester, United Kingdom

Andrew Reeve