Integration of different kinds of traffic on the Internet can be resolved by employing QoS policies on access networks. One possible solution is to use WTFC (Window-Time Flow Control) flow control algorithm on access network. In this paper, the WTFC-TCP flow control proxy is introduced in order to exploit the ability of WTFC to estimate the optimal working point for the available capacity and to keep on average empty node buffers. A basic proxy model is defined and elementary congestion signaling algorithms for flows directed to and from access network are applied. Simulation experiments have shown potential successfulness of the concept.