In cloud computing environments, QoS of network applications (NW-Apps) may degrade due to location factors such as significant distance between a server-side application (server) of a NW-App at a data center and a client-side application (client) at a client terminal. In order to shorten the distance and to improve the QoS, server migration services (SMSes) have been proposed. In SMSes, computers called work places (WPs) are deployed at various locations in a network, and servers can migrate between WPs to come close to their clients and attain better QoS. In this research theme, we investigate a server location decision algorithm that aims at keeping the QoS of NW-Apps as good as possible under the constraint that the server migration traffic has to be suppressed below an acceptable level.