Packet transmission scheduling with threshold based backpressure mechanism

A method of transmitting streams of packetized information over corresponding channels of an information network, comprising:

• associating two or more queues with each of a number of corresponding transmission channels of the network, enqueuing incoming descriptors representing first packetized information be transmitted over a given channel in a first queue associated with the given channel, and dequeuing incoming descriptors representing second packetized information to be transmitted over the given channel in a second queue associated with the channel wherein the second information has a transmission priority less than that of the first information;
• dequeuing the descriptors in said queues by operation of a scheduler;
• associating a number of transmit buffers with the transmission channels;
• defining for each of the transmit buffers a watermark threshold value corresponding to a desired minimum occupancy for the buffer, sensing when the occupancy of a given transmit buffer falls below the threshold value defined for the buffer, and producing a corresponding watermark event signal identifying the channel associated with the buffer;
• providing the watermark event signals to the scheduler, loading information represented by descriptors dequeued by the scheduler into corresponding transmit buffers according to the order of watermark event signals provided to the scheduler, and, for a given channel, loading the first information represented by descriptors enqueued in the first queue associated with the channel in a corresponding buffer ahead of the second information represented by descriptors enqueued in the second queue associated with the channel;
• and
• setting a capacity for each transmit buffer to correspond to two maximum byte sized packets.

An arrangement for transmitting packets of information over corresponding transmission channels of an information network, comprising:

• a controller configured to control operations of components of the system and the timing of said operations;
• a number of queues associated with the transmission channels of the network;
• said queues are constructed and arranged to enqueue incoming descriptors representing information to be transmitted over a given channel in a queue associated with the given channel;
• a number of transmit buffers associated with the transmit channels;
• the controller is configured to define for each of the transmit buffers a watermark threshold value corresponding to a desired minimum occupancy for the buffer, to sense when the occupancy of the given buffer falls below the threshold value defined for the buffer, and to produce a corresponding watermark event signal identifying the channel associated with the given buffer;
• and
• a scheduler coupled to said controller and responsive to the watermark event signals, wherein said scheduler is configured to dequeue the descriptors from the queues associated with the transmission channels, and to deliver information packets represented by the descriptors to corresponding transmit buffers according to the order of the watermark event signals produced by the controller, said information packets have a set maximum packet size, and the transmit buffers have capacities corresponding to two maximum byte sized packets.