Handling very large numbers of messages in Distributed Hash Tables

The principal service of Distributed Hash Tables (DHTs) is route(id, data), which sends data to a peer responsible for id, using typically O(log(# of peers)) overlay hops. Certain applications like peer-to-peer information retrieval generate billions of small messages that are concurrently inserted into a DHT. These applications can generate messages faster than the DHT can process them. To support such demanding applications, a DHT needs a congestion control mechanism to efficiently handle high loads of messages. In this paper we provide an extended study on congestion control for DHTs: we present a theoretical analysis that demonstrates that congestion control for DHTs is absolutely necessary for applications that provide elastic traffic. We then present a new congestion control algorithm for DHTs. We provide extensive live evaluations in a ModelNet cluster and the PlanetLab test bed, which show that our algorithm is nearly loss-free, fair, and provides low lookup times and high throughput under cross-load.