a packet flow control method where delay data are added into an initial packet as it traverses a packet switching network , and where the receiver of the initial packet , rather than the sender , establishes a window size based on such delay data to be used for the duration of a packet connection through the network . the delay data allow for the calculation of an average rather than an instantaneous network delay such that the flow control mechanism is not dependent on the magnitude of network congestion that happens to be present when the connection is first established . since the receiver determines the window size , the flow control mechanism is put in place as an integral part of the initial packet exchange used to establish the two - way packet connection rather than requiring an additional packet communication to the receiver after a window size calculation by the sender .