Still alive: Extending keep-alive intervals in P2P overlay networks

Nodes within existing P2P networks typically exchange periodic keep-alive messages in order to maintain network connections between neighbours. This paper investigates a number of algorithms which allow each individual connections to extend the interval between successive keep-alive messages based upon the likelihood that a corresponding node will remain in the system. Several studies have shown that older peers are more likely to remain in the network longer than their short-lived counterparts. Therefore using the distribution of peer session times and the current age of peers as key attributes, we propose three algorithms that increase the interval between successive keep-alive messages as nodes become more reliable. By prioritising keep-alive messages to nodes that are more likely to fail, our algorithms reduce the expected delay between failures occurring and their subsequent detection. Failed connections can incur expensive lookup timeouts and increases the network's vulnerability to partitioning. We extensively analyse the properties of these algorithms and compare them to the standard periodic keep-alive mechanism using simulations based upon measured network data.