Additional Reference Information
Ack Coalescing Detail
Coalescing Can Correct for Missing Ack
A requester may not receive the request packet Ack for one of three reasons:
The request packet was lost in the fabric and was not received by the responder.
The responder received the request packet but failed to generate an Ack packet.
The responder generated an Ack packet, but it was lost in the fabric.
This type of error is often automatically corrected by Ack coalescing. There are some cases, however, where Ack coalescing does not automatically make up for missing Ack packet(s). As an example, a lost Ack packet containing a Nak isn't resolved by Ack coalescing because the responder cannot have more than one Nak outstanding at a given time.