System and method for controlling communications network traffic through phased discard strategy selection
First Claim
1. A method for controlling congestion at an output from a node in a data communications network wherein data is transmitted in packets, each packet having a discardability characteristic, said method comprising the steps of:
- establishing a set of available, alternative discard strategies for packets having different discardability characteristics;
maintaining a profile of packets recently received at the output, the profile reflecting the discardability characteristics of said packets;
monitoring the output to detect the onset of congestion;
upon detection of congestion, using the profile to select an initial discard strategy; and
initiating the selected initial discard strategy.
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Abstract
Congestion at an output from a node in a packet data communications network is controlled by maintaining a traffic profile based on the discardability/priority characteristics of recently received packets and by selecting at least an initial discard strategy which should be effective in ending congestion based on that profile. The profile is established by maintaining counts of the number of packets actually stored in an output buffer and of the number of packets which would have been stored if different discard strategies had been in force. The relationship of certain of the count values to a threshold determines which discard strategy is initially selected. Different, successively less intrusive discard strategies can be implemented until the congestion ends.
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Citations
10 Claims
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1. A method for controlling congestion at an output from a node in a data communications network wherein data is transmitted in packets, each packet having a discardability characteristic, said method comprising the steps of:
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establishing a set of available, alternative discard strategies for packets having different discardability characteristics;
maintaining a profile of packets recently received at the output, the profile reflecting the discardability characteristics of said packets;
monitoring the output to detect the onset of congestion;
upon detection of congestion, using the profile to select an initial discard strategy; and
initiating the selected initial discard strategy. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A system for controlling congestion at an output buffer in a node in a packet data communications network, said system comprising:
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a first counter for maintaining a count n of the number of packets actually stored in the output buffer;
a plurality of additional counters, each additional counter being associated with a different predetermined discard strategy and maintaining a count of the number of packets which would have been stored in the ouput buffer had the associated discard strategy been in effect during receipt of the last n packets;
discard initiation logic for generating a congestion-detected signal when the count n exceeds a predetermined high threshold;
discard strategy selection logic for selecting and initiating one or more sequential discard strategies as a function of the counts maintained in said plurality of additional counters; and
discard termination logic for terminating discarding of packets when the count n falls below a predetermined low threshold. - View Dependent Claims (9, 10)
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Specification