Static and dynamic flow control using virtual input queueing for shared memory ethernet switches

摘要

A virtual input queue 80 count frames of data arriving an input port zo in an Ethernet switch 10 using shared memory 50. The shared memory 50 is allocated among 1-N input ports based on either a static or dynamic memory scheme. The static scheme allocates the shared memory 50 evenly among the input ports 20 or based on the input port transmission rate. In the dynamic memory scheme, the range of a virtual input queue's occupancy is divided into an underload zone, a normal load zone and an overload zone. When the virtual input queue is in the underload zone, the input port is kept on and reserved a memory capacity equal to a low threshold. When a virtual input queue is in the normal load zone, the virtual on queue 80 is reserved an additional amount of memory and the link is kept on or is turned on whenever possible. The memory capacity not used or reserved by any input port operating in at least the underload zone and normal load zone is shared by the input ports operating in the overload zone. A dynamic threshold is calculated at each of a control epoch for the input ports 20. The input ports 20 whose virtual input queue's value exceeds the threshold are turned off (or kept off). The ports whose virtual input queue's value is below the threshold are turned on (or kept on).