Method and apparatus for credit-based flow control in Fibre Channel systems

(57) Summary fiber channel credit エクステンダ (FCCE) (600) is a network device which is arranged between a termination node (210) and an optical translator (220), and is connected to both. FCCE (600) contains a required number of buffer credits in order to solve the problem of the bandwidth in a network. In the situation which needs maximum band width, FCCE (600) divides one logical link into three the "link let" separated physically in the both directions of a link. Short distance link let attains maximum band width by use of the existing buffer credit of a termination node. Long-distance link let attains maximum band width by use of the very big receive buffer credit of FCCE (600). In this way, that it needs to be connected to FCCE (600) becomes only a link which needs maximum band width in the distance which a termination node credit count does not cover. FCCE (600) contains the big credit count receive buffer in order to acquire distance on the link and to obtain bandwidth on the link including an optical translator. All other ports of a switch can have a still smaller cheap receive buffer.