I. Introduction
Network distance is often defined as the communication latency between two nodes, in the form of round-trip-time (RTT). Many Internet applications can benefit from the knowledge of whole network end-to-end distance such as overlay routing [1], peer-to-peer file sharing [2], mobile edge computing [3], and content delivery network. For instance, in content delivery networks, the end-user can conveniently obtain its desired web resources from a well-selected web server with the smallest network distance [4].