Fuzzynet: Zero-maintenance Ringless Overlay

Many structured overlay networks rely on a ring invari- ant as a core network connectivity element. The responsibil- ity ranges of the participating peers and navigability prin- ciples (greedy routing) heavily depend on the ring struc- ture. For correctness guarantees, each node needs to ea- gerly maintain its immediate neighboring links - the ring invariant. However, the ring maintenance is an expensive task and it may not even be possible to maintain the ring invariant continuously under high churn, particularly as the network size grows. Furthermore, routing anomalies in the network, peers behind firewalls and Network Address Translators (NATs) create non-transitivity effects, which in- evitably lead to the violation of the ring invariant. We argue that reliance on the ring structure is a serious impediment for real life deployment and scalability of structured over- lays. In this paper we propose an overlay called Fuzzynet, which does not rely on the ring invariant, yet have all the functionalities of structured overlays. Fuzzynet takes the idea of lazy overlay maintenance further by dropping any explicit connectivity and data maintenance requirement, re- lying merely on the actions performed when new Fuzzynet peers join the network. We show that with sufficient amount of neighbors (O(logN), comparable to traditional struc- tured overlays), even under high churn, data can be re- trieved in Fuzzynet w.h.p. We validate our novel design principles by simulations as well as PlanetLab experiments and compare it with ring based overlays.