buffer-to-buffer credit (BBC)

The buffer-to-buffer credit (BB_Credit or BBC) is used in Fibre Channel( FC) and serves to extend the distance range in storage networks. In general, there is a length limitation in storage networks with fiber optic paths, which is caused by the propagation time of the light signals in the fiber.

For longer distances, the data throughput decreases because the propagation times between data source and data receiver and back increase. Buffer-credit or buffer-to-buffer-credit techniques use memory expansion to overcome these limitations. This method can be used to bridge distances of several hundred kilometers. Buffer credit is a credit procedure in which a certain number of data packets are sent to the remote buffer without a positive acknowledgement( ACK). For each data packet sent, buffer credit reduces the specified number of packets by 1, and for each positive acknowledgement (ACK) the number increases by one data packet.