Cisco Systems, Inc.
Use of virtual lanes to solve credit stall on target ports in FC SAN

Abstract:

A method is performed at a switch fabric that communicates with a storage array target port. The method includes sending frames to the target port responsive to receiving buffer-to-buffer (B2B) credits that indicate a receive buffer at the target port is available for the frames. The method further includes, in response to detecting a credit stall at the target port, operating in a virtual lane mode. The operating in the virtual lane mode includes: determining whether a frame destined for the target port is a command frame or a data frame; based on the determining, marking the frame to indicate that the frame is destined for a particular virtual lane among virtual lanes of the receive buffer; and receiving from the target port a per-virtual lane B2B credit that indicates the particular virtual lane is available and, in responsive, sending the frame to that virtual lane on the target port.