Unacknowledged fabric frame flow is where there is no acknowledgment (at a Fibre Channel level) of the receipt of a frame: • Typically this is used in Class 3 which does not use end-to-end (EE) frame acknowledgement, so the transmitting port must assume that each frame has been delivered correctly.
• It is the responsibility of the receiving port to indicate whether an error has occurred and inform its upper layer protocol. Unfortunately, if the error occurs at the end of a sequence of frames, the transmitting port may have already emptied its ULP data buffers so cannot attempt a retry.