On the difficulty of finding the nearest peer in p2p systems

Finding the nearest peer, in terms of latency, is an important problem in many Internet applications. In this paper, we argue that existing solutions, which only examine inter-peer latencies as part of their operation will find it costly, in certain commonly occurring scenarios, to discover the nearest peer in P2P systems. The difficulty arises out of the way the PoP access networks are laid out in the Internet, where a single PoP (point of presence) belonging to an ISP provides connectivity to numerous client networks. This setup makes a group of peers all appear roughly the same distance from each other, leading to inefficiencies in the existing solutions. In this paper, we use large-scale measurements to show that the problematic topology does occur, use simulations of the Meridian closest-server algorithm to show that the condition does indeed lead to difficulty in finding the exact-closest peer, and propose solutions.