Method and system for implementing congestion detection and flow control in high speed digital network

A system for performing congestion detection and flow control operations over data traffics in a high speed digital packet switching network including access and transit nodes interconnected by links or trunks, each node including adapters with receive and transmit sections respectively attached to node entering and exiting links or trunks and switching means for transferring data packets from receive to transmit adapter sections, and wherein for any source end-user attached to said network via an entry access node and requesting its traffic to be vehiculated toward a destination end-user also attached to said network via an exit access node, so-called forward and returning (or backward) paths are set from said entry node to said exit node and in the opposite direction from said exit node to said entry node, respectively, which paths might include network transit nodes, each said end-user's traffic being either qualified as high priority level committed traffic whose delivery is guaranteed and assigned predefined transmission rate limits whereby a predefined amount of total transmission bandwidth is being reserved to it accordingly, or qualified low priority level discardable excess traffic and assigned whatever bandwidth is left, said system being characterized in that it includes:

• means in said adapter transmit section for dispatching the data packets, each packet including a so-called payload section and a so-called header section, toward output queues based on said priority levels;
• means for monitoring the data flow in said output queues in each node over the forward path from said entry node to said exit node, for detecting traffic congestion in said monitored queues and in case of flow congestion being detected therein, setting a so-called Congestion Indication (CI) bit field selected for carrying Explicit Forward Congestion Information (EFCI) in a first predefined header section of forward data packets, on the involved path down to the exit node;
• means for monitoring the incoming data packet entering said exit node, and in case of a set CI indication being detected therein setting a Return Congestion Indication (RCI) bit in a second predefined header section field in the data packets of the traffic flowing over said backward path;
• means in said entry node for monitoring the packets received from said backward path and for integrating monitored RCi bits over a predefined time-out period;
• means for monitoring said time period and at time-out indication, comparing said integrated RCI indication to at least one predefined threshold level and for controlling accordingly the bandwidth adjustment means in the involved receive adapter section of said entry node for adjusting the communication bandwidth assigned to said discardable traffic over said forward path, from said entry node to said exit node in a predefined manner.

For use in a packet switching network wherein a first connection is established to enable transmission of packets from a first node to a second node and a second connection is established to enable transmission of packets from the second node to the first node, wherein said second node monitors each packet received on the first connection for the presence of congestion indicators and responds to such indicators by setting a congestion indicator in packets later transported on the second connection and wherein packets may be designated as low priority or high priority packets, a congestion control system implemented in the first node comprising:

• a timer that times out at the conclusion of successive predetermined periods of time;
• an integrating circuit which maintains an integration result reflecting the number of congestion indications detected in packets received on said second connection;
• congestion detection logic responsive at the conclusion of each of the successive predetermined periods of time to obtain the current integration result and to reset the integrating circuit;
• and
• bandwidth control logic which adjusts the bandwidth allocated to low priority traffic on the first connection as a function of the obtained current integration result.