The problems on how to plan on the server′s network capacity and its network images in a digital library are considered. The focus is on the design of the total outer network capacity of the servers. A method of call blocking probability is proposed to evaluate the readers' satisfication about the provided services. The readers are classified in accordance with their network information transferring rates and an appropriate bandwidth is reserved for each kind of readers in achieving fair service quality. The methods of calculating the quality indexes of service and the capacity for the expected service are both presented and the feasibility of the method is shown through numerical examples.