Network data flow control technique

DETAILED DESCRIPTION We claim: 1.
A system for controlling the flow of data in a communication network of the kind in which a plurality of data streams are sent from an upstream node to a downstream node via a respective plurality of data paths carried on a link connected between said nodes, comprising means for said downstream node to specify information concerning permissible speeds of said data streams on the respective paths, and means for said upstream node to update the speeds of said plurality of data streams when necessary in response to said information.
2.
The system of claim 1 wherein said means to specify comprises means for considering when changes in said speeds will be specified by said downstream node, and means for identifying data paths whose speeds are to be changed.
3.
The system of claim 2 wherein said means for identifying data paths comprise means for comparing the previously specified speed of each said path with an ideal speed for said path, and means for selecting a data path for a speed change based on said comparison and on said level of buffer utilization.
4.
The system of claim 3 wherein said buffer means comprises a plurality of buffers allocated to respective said paths and said means for comparison further bases said ideal speed on the level of buffer utilization of said buffers allocated to a given said path.
5.
The system of claim 4 wherein said ideal speed is reduced when the level of buffer utilization of said allocated buffers exceeds a maximum.
6.
The system of claim 5 wherein said maximum comprises said allocated buffers containing two seconds worth of data bytes at said ideal speed prior to said reduction.
7.
The system of claim 3 wherein said comparison is a ratio and said path is selected for a speed change if said ratio exceeds a threshold that varies with the level of buffer utilization of said buffer.
8.
The system of claim 7 wherein said threshold increases with higher utilization levels.
9.
The system of claim 7 wherein there is one said threshold that never exceeds unity for speed decreases and a second said threshold that is never less than unity for speed increases