Used by all Class 2 and Class 3 frames and Class 1 for the connect request frame
The implication of an R_RDY is that the Receiver has reserved a buffer of the agreed Receive Data Field Size
Node
R_RDY
BB Flow Control
Switch
R_RDY
BB Flow Control
Node
Buffer-to-buffer (BB) flow control in a fabric: • Typically used between the device N_Port and the switch F_Port when a switch is present
• Used to maintain flow control only between these two points • Independent of, and asynchronous to, any other flow control mechanisms in the fabric
BB flow control in an arbitrated loop: • Arbitrated Loop topologies operate as virtual point to point circuits between a source and destination port—that is, between the communicating node ports, not the next connected port on the loop.
• Therefore there is little difference between using Class 3 to send a frame and receive an R_RDY, or using Class 2 to send a frame and receive an ACK frame.