A data transferring system for transmitting data from a transmission source to a transmission destination of a process control system established in a plant, comprising: a switch (11, 12) configured to transfer data from the transmission source to the transmission destination with reference to a table (TB1, TB2) in which a first information and a second information are associated, the first information representing a condition for performing a control of transferring received data, and the second information representing a processing which is to be performed when the condition represented by the first information is satisfied; and a controller connected to the switch (11, 12) via a network, the controller comprising a setter, an obtainer and an updater, wherein in case that a route between the transmission source to the transmission destination is unknown: the setter is configured to set via the network a tentative table, which is stored in a memory and in which the first information and the second information are associated, to the switch (11, 12) as the table (TB1, TB2), the obtainer is configured to obtain via the network a route information representing a route between the transmission source and the transmission destination, and the updater is configured to update the tentative table stored in the memory in accordance with the route information if the obtainer obtains the route information; wherein the switch (11, 12) comprises a first switch (11, SW1) and a second switch (12, SW2), wherein the controller is established in a hierarchy of level 3 specified by the international standard IEC/ISO 62264, in a process control system in a plant, wherein the first switch (11, SW1) is established between a hierarchy of level 2 and a hierarchy of level 3 specified by the international standard IEC/ISO 62264, in the process control system, wherein the second switch (12, SW2) is established between a hierarchy of level 3 and a hierarchy of level 4 specified by the international standard IEC/ISO 62264, in the process control system, and wherein the updater is configured to update the tentative table in accordance with the route information at a timing when the transmission source transmits data to the transmission destination for the first time after the obtainer obtains the route information. a switch (11, 12) configured to transfer data from the transmission source to the transmission destination with reference to a table (TB1, TB2) in which a first information and a second information are associated, the first information representing a condition for performing a control of transferring received data, and the second information representing a processing which is to be performed when the condition represented by the first information is satisfied; and a controller connected to the switch (11, 12) via a network, the controller comprising a setter, an obtainer and an updater, wherein in case that a route between the transmission source to the transmission destination is unknown: the setter is configured to set via the network a tentative table, which is stored in a memory and in which the first information and the second information are associated, to the switch (11, 12) as the table (TB1, TB2), the obtainer is configured to obtain via the network a route information representing a route between the transmission source and the transmission destination, and the updater is configured to update the tentative table stored in the memory in accordance with the route information if the obtainer obtains the route information; the setter is configured to set via the network a tentative table, which is stored in a memory and in which the first information and the second information are associated, to the switch (11, 12) as the table (TB1, TB2), the obtainer is configured to obtain via the network a route information representing a route between the transmission source and the transmission destination, and the updater is configured to update the tentative table stored in the memory in accordance with the route information if the obtainer obtains the route information; wherein the switch (11, 12) comprises a first switch (11, SW1) and a second switch (12, SW2), wherein the controller is established in a hierarchy of level 3 specified by the international standard IEC/ISO 62264, in a process control system in a plant, wherein the first switch (11, SW1) is established between a hierarchy of level 2 and a hierarchy of level 3 specified by the international standard IEC/ISO 62264, in the process control system, wherein the second switch (12, SW2) is established between a hierarchy of level 3 and a hierarchy of level 4 specified by the international standard IEC/ISO 62264, in the process control system, and wherein the updater is configured to update the tentative table in accordance with the route information at a timing when the transmission source transmits data to the transmission destination for the first time after the obtainer obtains the route information.