The invention relates to techniques for controlling a dynamic hitless resizing in data transport networks. According to a method aspect of the invention, a network connection comprises M tributary slots defined in a payload area of a higher order transport scheme of the data transport network and the method comprises the steps of receiving a connection resize control signal at each of the nodes along the path of the network connection; adding at each node along the path in response to the connection resize control signal a second set of N tributary slots to the first set of the M tributary slots, such that the network connection comprises M+N tributary slots; and increasing, after M+N tributary slots are available for the network connection at each node along the path, a transport data rate of the network connection.