– At port login, receiver tells transmitter how many buffers it has and what size they are
• Alternate credit management model:
– At port login, receiver tells transmitter how many buffers it can guarantee
– This method is requested during login – Allows ports to grant a Login Credit of 0 (default) – Ports do not need to guarantee buffer availability – Added to improve efficiency and reduce implementation cost – Default mode in Arbitrated Loop topology
Base credit management model is used in a Fabric Topology Alternate credit management model is used by Arbitrated Loop
Arbitrated Loop topologies must use the Alternate management model for operational reasons: • If the Base management method is used in an Arbitrated Loop topology, a port must grant maximum credit (total number of buffers) to all of the other ports in the loop. Theoretically, each of these other ports could all send frames and overrun the buffers in the receiving port resulting in frame loss.