A network system, comprising: a plurality of nodes, wherein the plurality of nodes transmit uplink and downlink traffic, using a path having a tree structure that includes one root node, a plurality of internal nodes, and a plurality of leaf nodes, wherein the root node comprises: a core node, CN, communication section that transmits a downlink frame to the plurality of internal nodes and the plurality of leaf nodes; and a transmission standby time determination section that determines a transmission standby time when the downlink frame is transmitted, wherein: the transmission standby time determination section determines the transmission standby time calculated by adding an additional standby time to a quality assurance time, the additional standby time being different according to destination node and the quality assurance time being a random backoff, and in a case where the root node transmits the downlink frame the transmission standby time determination section determines the transmission standby time, and the CN communication section transmits the downlink frame after the transmission standby time elapses after transmission of a downlink frame that is immediately before the downlink frame to be transmitted. a plurality of nodes, wherein the plurality of nodes transmit uplink and downlink traffic, using a path having a tree structure that includes one root node, a plurality of internal nodes, and a plurality of leaf nodes, wherein the root node comprises: a core node, CN, communication section that transmits a downlink frame to the plurality of internal nodes and the plurality of leaf nodes; and a transmission standby time determination section that determines a transmission standby time when the downlink frame is transmitted, a core node, CN, communication section that transmits a downlink frame to the plurality of internal nodes and the plurality of leaf nodes; and a transmission standby time determination section that determines a transmission standby time when the downlink frame is transmitted, wherein: the transmission standby time determination section determines the transmission standby time calculated by adding an additional standby time to a quality assurance time, the additional standby time being different according to destination node and the quality assurance time being a random backoff, and in a case where the root node transmits the downlink frame the transmission standby time determination section determines the transmission standby time, and the CN communication section transmits the downlink frame after the transmission standby time elapses after transmission of a downlink frame that is immediately before the downlink frame to be transmitted. the transmission standby time determination section determines the transmission standby time calculated by adding an additional standby time to a quality assurance time, the additional standby time being different according to destination node and the quality assurance time being a random backoff, and in a case where the root node transmits the downlink frame the transmission standby time determination section determines the transmission standby time, and the CN communication section transmits the downlink frame after the transmission standby time elapses after transmission of a downlink frame that is immediately before the downlink frame to be transmitted. the transmission standby time determination section determines the transmission standby time, and the CN communication section transmits the downlink frame after the transmission standby time elapses after transmission of a downlink frame that is immediately before the downlink frame to be transmitted. <EOS>