Abstract: A data communications system includes optic adaptors that provide an interface between multiple line card chassis and a fabric card chassis. Optic adaptors can be added to the system to allow the addition of a number of line card chassis, thereby increasing the overall bandwidth of the system. The optic adaptors can also be separated from the fabric card chassis and line card chassis and upgraded to allow an increase in the overall bandwidth of the system. For example, optic adaptors that provide optical connections between a first number of line card chassis and the fabric card chassis can be detached from both the fabric card chassis and the respective line card chassis. Optic adaptors that provide optical connections between the fabric card chassis and a second, increased number of line card chassis are then installed within the fabric card chassis thereby allowing the additional line card chassis to be connected to the fabric card chassis.

Abstract: A method and apparatus for applying selective backpressure to control a multi-stage interconnection network (MIN). At one or more stages in the MIN, local information is used to define a queue status parameter for each local queue in the fabric. At the egress linecard, the upstream queue status parameter is periodically combined with the egress linecard's output queue status to generate a queue-specific backpressure signal. The backpressure signal continuously indicates to the ingress linecard that a specific fabric queue or queues is experiencing congestion and that the ingress linecard should therefore slow down or stop sending additional packets to the affected queue. Status computation mechanisms, which are state machines in one embodiment of the present invention, are incorporated in each switch element in at least the last stage of the switch fabric.