Data communication system, data communication method, data communication apparatus and digital interface

There is disclosed a communication system and communication protocol in which a source node (28) and one or more destination nodes (60) are logically connected, and a connection ID for identifying the logical connection relationship is used to control data communication between the nodes. There is also disclosed an efficient communication system and communication protocol in which an optimum time interval between a time to transmit an i-th (i being an optional integer) data and a time to transmit an (i+1)-th data can be set. There is further disclosed a communication system and communication protocol in which when the i-th data is not normally received, retry is inhibited only for a predetermined time to prevent the retry from unnecessarily occurring between a destination node slow in receiving process and a source node fast in transmitting process.