In network systems design, it is often difficult to quantify the impact of network performance brought by the requirement changes because of the complexities and dependencies among the changed and unchanged requirements. In this paper, the relations of these dependencies such as bandwidth size, number of user etc are analyzed and established. The scope of the impact caused by requirement changes is identified using Kraft inequality and the impact was quantified. A minimal closure algorithm developed to quantitatively evaluate the effect of requirement changes is presented. Lastly, the feasibility of this evaluation algorithm is shown through a case study.