A transmission system comprising: a first pair of transmission devices (10-1, 10-7) that are a transmission device serving as an end point of a reception side for a first traffic of transmission unit data and another transmission device serving as an end point of a transmission side for the first traffic, one or more first intermediate transmission devices (10-3, 10-4, 10-5) that are located between said another transmission device serving as the end point of the transmission side for the first traffic and the transmission device serving as the end point of the reception side for the first traffic, a second pair of transmission devices (10-2, 10-6) that are a transmission device serving as an end point of a reception side for a second traffic of transmission unit data and another transmission device serving as an end point of a transmission side for the second traffic, and one or more second intermediate transmission devices (10-3, 10-4) that are located between said another transmission device serving as the end point of the transmission side for the second traffic and the transmission device serving as the end point of the reception side for the second traffic, wherein the first intermediate transmission devices (10-3, 10-4, 10-5) and the second intermediate transmission devices (10-3, 10-4) share the same physical link, the transmission device serving as the end point of the reception side for the first traffic comprises: a reception buffer which temporarily accumulates received transmission unit data; a signal generation section (123, 124, 126, 127) which generates a control signal for instructing to stop transmission of transmission unit data, the control signal being to be transmitted via the first intermediate transmission devices (10-3 10-4, 10-5) to said another transmission device serving as the end point of the transmission side for the first traffic, when an amount of accumulation in the reception buffer has exceeded a predetermined upper-limit threshold value, thereby without stopping the second traffic via the same physical link as that of the first link; and a transmission section (128, 129) which transmits the control signal. a first pair of transmission devices (10-1, 10-7) that are a transmission device serving as an end point of a reception side for a first traffic of transmission unit data and another transmission device serving as an end point of a transmission side for the first traffic, one or more first intermediate transmission devices (10-3, 10-4, 10-5) that are located between said another transmission device serving as the end point of the transmission side for the first traffic and the transmission device serving as the end point of the reception side for the first traffic, a second pair of transmission devices (10-2, 10-6) that are a transmission device serving as an end point of a reception side for a second traffic of transmission unit data and another transmission device serving as an end point of a transmission side for the second traffic, and one or more second intermediate transmission devices (10-3, 10-4) that are located between said another transmission device serving as the end point of the transmission side for the second traffic and the transmission device serving as the end point of the reception side for the second traffic, wherein the first intermediate transmission devices (10-3, 10-4, 10-5) and the second intermediate transmission devices (10-3, 10-4) share the same physical link, the transmission device serving as the end point of the reception side for the first traffic comprises: a reception buffer which temporarily accumulates received transmission unit data; a signal generation section (123, 124, 126, 127) which generates a control signal for instructing to stop transmission of transmission unit data, the control signal being to be transmitted via the first intermediate transmission devices (10-3 10-4, 10-5) to said another transmission device serving as the end point of the transmission side for the first traffic, when an amount of accumulation in the reception buffer has exceeded a predetermined upper-limit threshold value, thereby without stopping the second traffic via the same physical link as that of the first link; and a transmission section (128, 129) which transmits the control signal. a reception buffer which temporarily accumulates received transmission unit data; a signal generation section (123, 124, 126, 127) which generates a control signal for instructing to stop transmission of transmission unit data, the control signal being to be transmitted via the first intermediate transmission devices (10-3 10-4, 10-5) to said another transmission device serving as the end point of the transmission side for the first traffic, when an amount of accumulation in the reception buffer has exceeded a predetermined upper-limit threshold value, thereby without stopping the second traffic via the same physical link as that of the first link; and a transmission section (128, 129) which transmits the control signal.