Patent ID: 7894348

Claim:
A method for controlling routing of fibre channel frames by a fibre channel switch element having a transmit segment with a plurality of queues for transmitting frames and a receive segment for receiving frames, comprising: (a) setting a first threshold value to control frame transmission from the plurality of queues of the transmit segment of a port of the fibre channel switch; wherein the first threshold value includes a number of primitives (R_RDYs) that a queue from among the plurality of queues of the transmit segment has to receive before the queue is permitted to transmit a frame; the number of primitives (R_RDYs) indicating available credit at a receive segment of a destination port; (b) enabling a credit limiting feature by counting a number of credits that are outstanding for the port at any given time and comparing if the number of outstanding credits is greater than or equal to a second threshold value; wherein the credit limiting feature is set to limit frame transmission from the queue of the transmit segment even when the transmit segment has available credit to transmit an available frame; (c) incrementing a first counter value used for counting a number of R_RDYs that is received after a frame departs from the queue of the transmit segment; (d) comparing the first counter value with the first threshold value; (e) transmitting a frame from the queue of transmit segment when the first counter value is equal to or greater than the first threshold value indicating that the queue has received a certain number of R_RDYs from the receive segment of the destination port; and (f) when the credit limiting feature is enabled in step (b), blocking frame transmission from the queue of the transmit segment if the first counter value is less than the first threshold value, indicating that the queue of the transmit segment has to wait and receive more R_RDYs to match the first threshold value.