The issues on the interconnection of telecommunications network are recently prevailed in the IT industry. In this study, we classify the network interconnection system into two categories: two way-same price model and two way-different price model. The purpose of this paper is to analyze economic characteristics of optimal settlement system according to each model. One of the most important policy implications we derive through this study is that symmetry between enterprises is required for policy maker or regulatory agency to set an efficient settlement system under two way-same price model, but that symmetry is not necessarily required under two way-same price model.