Congestion control is an import issue in the broadband network, which aims at improving network utilization and fairness. Rate based closed loop feedback congestion control schemes and their various implementations in broadband networks are discussed. The high burstiness and strong correlations inherent in the network traffic are pointed out to be the key to the design of algorithm on congestion control, so is the delay time of the network. In addition, the goal for maximizing network utility often confilicts with the goal of fairness. All these show it is difficult to get a optimal scheme. Therefore, we denote that both the accurate description of the characteristics of the network traffic and the scubsequent design of the congestion control algorithm rely on necessary mathematical tools.