Transparency of resources is provided and ordering in an access is guaranteed between nodes on a computer network. In an information processing system in which a plurality of processor units are connected to each other by a switch, a global address space is introduced into which effective addresses of the processor units are mapped and which is shared by the plurality of processor units. In response to an access request packet issued by a processor unit and designating an effective address of a target node, a bridge for routing an input and output bus of a processor unit to an input and output bus of the switch converts the effective address of the target node into a global address by appending to the packet a node identification number identifying the target node, and outputs the access request packet designating the global address to the switch. After an access request packet for a write operation is output, the bridge confirms whether the write operation is completed in a target node.