Method and apparatus for round trip delay measurement in a bi-directional, point-to-point, serial data channel

Abstract

The link round trip delay between two switches in a Fibre Channel network may be determined by sending a particular timing signal value from an originating switch to a responding switch. The responding switch may store the timing signal value in an 'echo' register for comparison to subsequently received timing signals. The originating switch may then send the pre-selected timing signal to the responding switch while simultaneously starting a timer. When the responding switch receives the timing signal, it may compare the value of the received signal to that stored in its echo register. If the value, is the same, the responding switch may retransmit—i.e., echo—the timing signal to the originating switch. When the originating switch receives the echoed timing signal, it may stop its timer and compute the link round trip delay time. The computed link round trip delay time between the originating switch and the responding switch may be advantageously used in fabric routing algorithms.