Nortel Networks Corporation

Peter Martin Kenneth Cottreau

David MacDonald Delaney

Alan Hurren

Wang-Hsin Peng

Mark Temple Cobbold

Bijan Raahemi

Lutful Khan

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

An algorithm for media access control over nodes in a buffer insertion ring is described. Each node computes a local add rate and an advertised rate which it communicates to its upstream link partner node. The rate calculations are based on a locally computed tandem rate and a downstream rate received from a downstream link partner node. The algorithm ensures rapid convergence to a fair add rate at which nodes share link resources to avoid starvation in the ring. The advantages include short head of line delay, low operating overhead, and good bandwidth utilization.

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Ashton, Canada

Peter Martin Kenneth Cottreau