Chord on Demand

Structured peer-to-peer overlay networks are now an established paradigm for implementing a wide range of distributed services. While the problem of maintaining these networks in the presence of churn and other failures is the subject of intensive research, the problem of building them from scratch has not been addressed (apart from individual nodes joining an already functioning overlay). In this paper we address the problem of jump-starting a popular structured overlay, Chord, from scratch. This problem is of crucial importance in scenarios where one is assigned a limited time interval in a distributed environment such as Planet-Lab, or a Grid, and the overlay infrastructure needs to be set up from the ground up as quickly and efficiently as possible, or when a temporary overlay has to be generated to solve a specific task on demand. We introduce T-CHORD, that can build a Chord network efficiently starting from a random unstructured overlay. After jump-starting, the structured overlay can be handed over to the Chord protocol for further maintenance. We demonstrate through extensive simulation experiments that the proposed protocol can create a perfect Chord topology in a logarithmic number of steps. Furthermore, using a simple extension of the protocol, we can optimize the network from the point of view of message latency.