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The Internet uses a window-based flow control mechanism in TCP (Transmission Control Protocol). There have been a significant number of analytical studies on TCP. Most, however, have focused on the statistical behavior of TCP by assuming a constant packet loss probability in the network. In our previous work, we presented an approach for modeling the network as a single feedback system using the fluid flow approximation and queuing theory. By utilizing and extending our previous work, we analyze the steady state behavior and transient behavior of TCP. We first derive the throughput and packet loss probability of TCP, and the number of packets queued in the bottleneck router We then analyze the transient behavior of TCP using a control theoretic approach, showing the influence of the number of TCP connections and propagation delay on its transient behavior of TCP. Through numerical examples, it is shown that the bandwidth-delay product of a TCP connection significantly affects its stability and transient performance. It is also shown that, contrary to one's intuition, the network becomes more stable as the number of TCP connections and/or the amount of background traffic increases.