A flow model upon users' utility function was proposed, with which the optimization-based congestion control could transform optimization-based flow c ontrol. A dual gradient projection algorithm was given to optimize network flow control. In this algorithm, sources selected transmission rates that maximize th eir own benefits, utility minus bandwidth cost, and network links adjusted conge stion prices to coordinate the sources' decision. To implement this network flow control algorithm, the routers set ECN(explicit congestion notification) bit p robabilistically to transmit congestion price information. And the necessary lin k position information of packet path was estimated by exploiting the existing s emantics of the TTL(time-to-live) field in IP header. The computer simulation verified the convergence and validity of this flow control algorithm.