PURPOSE: To provide the frame relay system by which a transmission port is decided at a high speed without need of frequent use of a memory.

CONSTITUTION: Information (a) designating a transmission port for each reception port and sets of information (b),(c) representing whether or not each port is in a transmission enable state are expressed in a bit map form in the frame relay system for an inter-LAN connection communication controller provided with plural frames and the transmission port is decided by applying bit arithmetic operation to them. Since the port through which a frame is to be sent depends at once on the bit arithmetic operation, the processing speed of frame relay is increased and no much memory capacity is required.