Mobile communication system and transmitting-side node

In a mobile communication system, an AP/ULP layer of a transmitting-side node (A) acquires, from an SCTP layer of the transmitting-side node (A), an rwnd for each of a plurality of connections of the SCTP layer, a cwnd for each of a plurality of physical paths, a third data amount indicating the amount of data transmitted by the transmitting-side node per unit time for each of a plurality of streams.  When an emergency flag is included in transport data to be transmitted, the AP/ULP layer of the transmitting-side node (A) decides, based on the rwnd, cwnd and third data amount, a stream and a physical path that are to be used for transmitting the transport data and notifies the decided stream and physical path to the SCTP layer.