Network Overlay Construction under Limited End-to-End Addressability

Network overlay construction has found many applications in today’s Internet, such as P2P networks [1][2], end-host multicast [3][4], and network security [5]. Many researchers have proposed solutions to building an overlay network among a given group of end-hosts. The usual overlay construction assumes two-way network communication— each host can initiate connections to and accept requests from other hosts. This is not always true on the Internet due to the use of Network Address Translation (NAT) and firewalls. Our experiments with one P2P file-sharing system revealed that over 34% of hosts were guarded hosts, i.e., hosts that cannot accept connections from other Internet hosts. The lack of two-way communication capability presents a challenge because only a subset of hosts can act as overlay routers. Using a cluster-base approach, we design a new overlay construction mechanism called e*, which organizes members based on reachability and intelligently select overlay routers to reduce end-to-end latencies on the overlay. Under realistic scenarios involving guarded hosts, e* can reduce average end-to-end latency on the overlay by 28-61% compared to existing protocols. Furthermore, e* significantly improves the worst case end-to-end latency on the overlay.