— A new communication model, called the PlogPT model, is proposed to predict communication performance in a commodity cluster where computing nodes communicate using TCP/IP. This model extends the PlogP model in order to consider the variation of bandwidth brought about by bottleneck links in network switches and the delay of packet retransmission by TCP/IP handling. Network switches are modeled as binary tree connections. To demonstrate the PlogPT model’s modeling capability, the execution time of two all-to-all communication algorithms are estimated and compared with the actual execution time and that of the PlogP model. The PlogPT model predicts the execution time of those two algorithms more precisely than the existing model.