Congestion control for cell networks

A feedback control system for congestion prevention control on a virtual connection of a cell switching communications network handling bursty traffic, comprising:

• a) a source node for accepting, queueing, and buffering user framed bursty data, for formatting the bursty data into bursty data cells, and for transmitting the cells over the virtual circuit connection through the cell switching communications network at an incrementally variable controllable transmission rate wherein the source node and any intermediate node comprising the virtual connection include means for accepting, queueing, and buffering the bursty data cells, means for detecting incipient congestion in the virtual connection queues and buffers, and means for forwarding the bursty data cells over the virtual connection together with an associated incipient congestion indicator;
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• b) a destination node, being the terminus of the communication network virtual connection for accepting the bursty data cells and the associated incipient congestion indicator, for reconstructing, formatting, and outputting the framed bursty data, for monitoring the congestion indicators, for creating a four state, two binary bit, rate control signal representing rate increase, rate decrease, fast rate decrease, and no-rate-change messages based on the congestion indicators, transmitting the rate control signal back to the source node, wherein the incrementally controllable transmission rate of the source node is adjusted in response to the rate control signal sent from the destination node in order to minimize congestion.

A feedback control system for congestion prevention control on a virtual connection of a cell switching communications network handling bursty traffic, comprising:

• a) a source node for accepting, queueing, and buffering user framed bursty data, for formatting the bursty data into bursty data cells, and for transmitting the cells over the virtual circuit connection through the cell switching communications network at an incrementally variable controllable transmission rate that is variable between a prescribed lower guaranteed minimum rate and an upper maximum rate, the source node and any intermediate node comprising the virtual connection include means for accepting, queueing and buffering the bursty data cells, means for detecting incipient congestion in the virtual connection queues and buffers, and means for forwarding the cells over the network virtual connection together with an associated incipient congestion indicator;
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• b) a destination node being the terminus of the communication network virtual connection having means for accepting the bursty data cells and the associated incipient congestion indicator, for reconstructing, formatting and outputting the framed bursty data, for monitoring the congestion indicators, for creating a rate control signal based on the congestion indicators, for transmitting the rate control signal back to the source node, wherein the incrementally controllable transmission rate of the source node is adjusted in response to the rate control signal sent from the destination node in order to minimize congestion.

A feedback control system for congestion prevention control on a virtual connection of a cell switching communications network handling bursty traffic, the feedback control system comprising:

• a) a source node for accepting, queuing and buffering user framed bursty data, for formatting the bursty data into bursty data cells, and for transmitting the cells over the virtual circuit connection through the cell switching communications network at an incrementally variable controllable transmission rate in response to a rate control signal to minimize congestion, the source node and any intermediate node comprising the virtual connection include means for accepting, queuing and buffering the bursty data cells, means for detecting incipient congestion in the virtual connection queues and buffers by monitoring the average queue length over a regeneration cycle time interval, means for comparing the average queue length to an incipient congestion threshold, means for setting an incipient congestion indicator to a first state when the incipient congestion threshold is exceeded and setting the incipient congestion indicator to a second state when the incipient congestion threhsold is not exceeded, and means for forwarding the cells over the network virtual connection together with the incipient congestion indicator;
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• b) a destination node being the terminus of the communication network virtual connection having means for accepting the bursty data cells and the incipient congestion indicator, for reconstructing, formatting, and outputting the framed bursty data, for monitoring the incipient congestion indicators, for revising the rate control signal based on the incipient congestion indicators, for transmitting the rate control signal back to the source node.

A feedback control system for congestion prevention control on a virtual connection of a cell switching communications network handling bursty traffic, comprising:

• a) a source node for accepting, queueing and buffering user framed bursty data, for formatting the bursty data into bursty data cells, and for transmitting the cells over the virtual circuit connection through the cell switching communications network at an incrementally variable controllable transmission rate, the source node and any intermediate node comprising the virtual connection having means for accepting, queueing and buffering the bursty data cells, means for detecting incipient congestion in the virtual connection queues and buffers, and means for forwarding the cells over the network virtual connection together with an associated incipient congestion indicator;
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• b) a destination node being the terminus of the communication network virtual connection having means for accepting the bursty data cells and the associated incipient congestion indicator, for reconstructing, formatting and outputting the framed bursty data, for counting cells with the associated incipient congestion indicator asserted, for creating a rate control signal based on the cell count, for transmitting the rate control signal back to the source node, wherein the incrementally controllable transmission rate of the source node is adjusted in response to the rate control signal sent from the destination node in order to minimize congestion.

A feedback control system for congestion prevention control on a virtual connection of a cell switching communications network handling bursty traffic, comprising:

• a) a source node for accepting, queueing and buffering user framed bursty data, for formatting the bursty data into bursty data cells, for indicating those cells derived from user input data received at rates exceeding a prescribed guaranteed minimum rate, and for transmitting the cells together with the indicators over the virtual circuit connection through the cell switching communications network at an incrementally variable controllable transmission rate, the source node and any intermediate node comprising the virtual connection having means for accepting, queueing and buffering the bursty data cells, means for detecting incipient congestion in the virtual connection queues and buffers, and means for forwarding the cells over the network virtual connection together with an associated incipient congestion indicator;
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• b) a destination node being the terminus of the communication network virtual connection having means for accepting the bursty data cells and the associated incipient congestion indicator, for reconstructing, formatting and outputting the framed bursty data, means for monitoring the congestion indicators, for creating a rate control signal based on the congestion indicators, means for transmitting the rate control signal back to the source node, wherein the incrementally controllable transmission rate of the source node is adjusted in response to the rate control signal sent from the destination node in order to minimize congestion.

A feedback control system for congestion prevention control on a virtual connection of a cell switching communications network handling bursty traffic, comprising:

• a) a source node for accepting, queueing and buffering user framed bursty data including an associated expendable data indicator that indicates an excess input frame data rate, for formatting the bursty data into bursty data cells, for encoding the expendable data indicator in the cell header, for discarding cells bearing the indicator for relief of congestion, and for transmitting the non-discarded cells over the virtual circuit connection through a cell switching communications network at an incrementally variable controllable transmission rate, the source node and any intermediate nodes comprising the virtual connection having means for accepting, queueing and buffering the bursty data cells, means for detecting incipient congestion in the virtual connection queues and buffers, and means for forwarding the cells over the network virtual connection together with an associated incipient congestion indicator;
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• b) a destination node being the terminus of the communication network virtual connection having means for accepting the bursty data cells and the associated incipient congestion indicator, for reconstructing, formatting and outputting the framed bursty data, for monitoring the congestion indicators, for creating a rate control signal based on the congestion indicators, means for transmitting the rate control signal back to the source node, wherein the incrementally controllable transmission rate of the source node is adjusted in response to the rate control signal sent from the destination node in order to minimize congestion.

A feedback control method for congestion prevention on a virtual circuit connection of a cell switching network handling bursty data traffic, the method comprising the steps of:

• a) queuing and buffering user bursty data frames at an input source node;
• b) formatting the bursty data frames into bursty data cells;
• c) queuing and buffering the bursty data cells within the input source node and intermediate nodes, for transmission to a next node of the virtual connection;
• d) detecting incipient congestion of the bursty data cells that are buffered and queued for transmission to the next node by monitoring queue lengths;
• e) setting an incipient congestion indicator to a first state when incipient congestion is detected;
• f) setting the incipient congestion indicator to a second state when incipient congestion is not detected;
• g) associating the incipient congestion indicator with corresponding cells that are contributing to the incipient congestion;
• h) transmitting the cells and incipient congestion indicators to the destination node over a virtual circuit connection at a controllable rate;
• i) incrementally controlling the transmission rate of bursty cells in response to a rate control signal so as to control congestion;
• j) reconstructing frames at the destination node from received bursty cells;
• k) monitoring the congestion indicators at the destination node for determining a congestion status of the virtual connection;
• l) revising the rate control signal based on the congestion status;
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• m) transmitting the rate control signal to the source node.