A peer-to-peer expressway over Chord

We introduce an auxiliary coarse-grained routing layer (an expressway) on Chord, a DHT based structured peer-to-peer system. With the assumption that nodes in the system have different resource capacities such as storages and bandwidths, powerful (high connectivity and bandwidth) nodes can join the expressway to perform fast routing. We design the logical structure of an expressway overlay. us on the design and analysis of the logical structure of the expressway overlay that is parameterized by a characteristic called the forwarding power p . Expressway nodes maintain more routing entries that can forward requests with a longer per hop distance than the underlying system. The expressway defers the “last mile” fine-grained routing to the underlying system. We also propose an event-based notification for membership and routing entry management on the expressway. Our initial experimental results of an expressway with a forwarding power of 4 show that the average logical path length of the system when over 20% of nodes join the expressway is about the same as when every node joins the expressway. The theoretical analysis shows that the logical routing path lengths of the system improve up to 1 − 2 ( p − 1 p ) log p 2 . The system requires O ( log 2 r ) messages to update all expressway routing entries when a node joins or leaves the system, where r is the number of expressway nodes.