buffer to buffer flow control (FC) (BB_Buffer)
Buffer to Buffer Flow Control (BB_Buffer) is a flow control that occurs in Fibre Channel( FC) between two directly connected FC ports, for example, an N_Port and an F_Port.
Before transmission, the corresponding port indicates the number of data frames it can buffer. Buffer-to-buffer flow control is used only when a local NL port logs into another NL port or when Nx ports log into Fx ports.