Nortel Networks Corporation

Canai Computer and Network Architecture Inc.

Plaintree Systems Inc.

David MacDonald Delaney

Alan Hurren

Peter Martin Kenneth Cottreau

David Milton

Wang-Hsin Peng

Mark Temple Cobbold

David P Schenkel

A control system enables transport of payload data across a dual counter rotating ring (DCRR) network having two or more nodes, each node providing access to the DCRR network by a respective local area network (LAN) subtending the node. The control system comprises a topology learning entity operative within each node for monitoring individual, links of the DCRR, discovering the active topology of the DCRR, communicating topology changes to other nodes in the DCRR, and informing frame forwarding and learning processes of the topology to enable failover to redundant resource upon detection of a network component failure. A frame forwarding process selects a shortest path route between a source and a destination node in the DCRR, and forwards frames to the destination node via the selected shortest path route. An address learning process inspects a source medium access control (MAC) address in each received frame to learn a shortest path route for each MAC address.

Enhanced dual counter rotating ring network control system

In methods and apparatus for routing packets through a communications network, a respective distinct broadcast address is assigned to each of a plurality of distinct sets of virtual ports. No virtual port belongs to more than one of the distinct sets. A respective egress address is assigned to each packet entering the network via an ingress virtual port. The respective egress address corresponds to a respective destination address of the entering packet when a correspondence between the destination address and an egress address is known. When no correspondence between the destination address and an egress address is known, the respective egress address is a broadcast egress address corresponding to the set comprising the ingress virtual port. The packet is routed according to the respective egress address. The routing is restricted to virtual ports belonging to the distinct set of virtual ports that includes the ingress virtual port. The distinct sets of virtual ports and their associated broadcast addresses define isolated virtual private networks within the network. Each physical port of the network may map one-to-one onto a corresponding virtual port, or may map onto a corresponding plurality of virtual ports, in which case the each virtual port of the plurality is associated with a respective distinct combination of a physical address of the physical port and a respective virtual network identifier.

Virtual private networks and methods for their operation

A transparent bridge between a pair of local area networks is comprised of a database for storing destination addresses for frames of data, a pair of frame transfer agents each connected to the database for transferring frames of data in respectively opposite directions from one LAN to the other depending on whether addresses stored in the database correspond to destination addresses of the frames of data.

High performance two-port transport LAN bridge

A unidirectional bus data communication system which eliminates uncertainty as to the integrity of data received by a receiver connected to the bus, which data may have been involved in truncating collisions. A plurality of data stations are connected to a unidirectional bus which has segments connected to and between the stations. Each of the stations is connected to an upstream segment by a sense (S) lead and to a downstream segment by a transmit (T) lead. Each station is adapted to sense energy via its S lead arriving on an associated upstream segment of the bus and includes a transmitter for transmitting data signals via its T lead on an associated downstream segment of the bus. Signal delay elements interconnect upstream and downstream segments of the bus bypassing each of the stations. The time delay D of each of the signal delay elements is a function of the total interval of a predetermined group of data signal bit durations of the data signals added to a period T.sub.d which is equal to the time between arrival of energy at an S lead and the instant when an associated transmitting means can, in response to such detection, stop transmitting energy on its T lead.

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Ottawa, Canada

David MacDonald Delaney