A framework for selecting appropriate content delivery server considering round-trip time and actual serving calls

CDN (content delivery networks) (K. Fujikawa et al., December 2002) is referred to network designed to efficiently deliver various service contents depending on the status of a network and a server. To construct a CDN, we should consider problems at three levels: network planning, content allocation, content delivery server selection. Specially, in terms of server selection, previous researches proposed to choose content delivery server based on real time information such as measured response time, delay from all delivery servers. However, these researches seemed to neglect two performance factors, call blocking probability and network load to control protocol. In this paper, we propose a new server selection algorithm considering the number of current serving calls in each delivery server and round-trip time (RTT) between user and content delivery server. In proposed algorithm, we introduce a new entity, administrative server (AS), which is used for making min heap structure. An AS maintains min heap structure, which indicates the number of current serving calls in each content delivery server. Using min heap structure, each user easily obtains appropriate content delivery server set and quickly selects delivery server from one without call blocking and long end-to-end delay.