In this thesis, the performance of an integrated voice/data packet communication network with window flow control is investigated. The network is modeled by tandem links with a single closed chain and analyzed. The data controlled by window flow control is analyzed with a heuristic method based on the mean value analysis approach and the concept of the effective capacity. For analysis of the network where the acknowledgement delay cannot be neglected and the priority scheduling scheme is used, we use a modified mean value analysis method. Also for analysis of the network having other messages such as voice and external data, we use the M/G/1 queueing theory with different priority classes. Using these methods, we obtain iteratively various network parameter values, such as throughput, mean queue length and delay time. In addition, we investigate the network performances for different window sizes, thereby obtaining the optimal window size that maximizes the network efficiency for different traffic intensities. Finally, the characteristics of voice and data traffics in packet computer network are investigated.