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.

Abstract: A packet based data transmission system includes a flexible optimized nonocking transmit interface that incorporates optimized buffer modes, dynamic and static chaining, streaming and the utilization of small packet formats. Static chaining refers to connecting together the linked list for successive packets for the same transmit channel or virtual channel. Dynamic chaining refers to means by which the network interface performs this chaining automatically, thereby solving a blocking problem. On the transmit side, streaming refers to initiating the transmission of packet data before the entire packet data has been presented to the interface. This, in turn, permits more rapid recycling of the buffer space. On the receive side, streaming refers to initiating the processing of packet data before the entire packet has been received.