Canon in G major: designing DHTs with hierarchical structure

Abstract

Distributed hash tables have been proposed as flat, nonhierarchical structures, in contrast to most scalable distributed systems of the past. We show how to construct hierarchical DHTs while retaining the homogeneity of load and functionality offered by flat designs. Our generic construction, Canon, offers the same routing state vs. routing hops trade-off provided by standard DHT designs. The advantages of Canon include (but are not limited to) (a) fault isolation, (b) efficient caching and effective bandwidth usage for multicast, (c) adaptation to the underlying physical network, (d) hierarchical storage of content, and (e) hierarchical access control. Canon can be applied to many different proposed DHTs to construct their Canonical versions. We show how four different DHTs - Chord, Symphony, CAN and Kademlia - can be converted into their Canonical versions that we call Crescendo, Cacophony, Can-Can and Kandy respectively.