A General Framework for Scalability and Performance Analysis of DHT Routing Systems

TL;DR

This paper introduces the reachable component method (RCM) to analyze and compare the scalability and robustness of various DHT routing systems under random node failures, providing analytical insights into their performance at large scales.

Contribution

The paper develops RCM as a unified analytical framework to evaluate DHT routing systems' scalability and robustness, revealing which systems remain effective at large network sizes.

Findings

Kademlia is scalable and robust at large scales.

Some DHT systems become unscalable with increasing network size.

Analytical expressions characterize routability as a function of network size and failure probability.

Abstract

In recent years, many DHT-based P2P systems have been proposed, analyzed, and certain deployments have reached a global scale with nearly one million nodes. One is thus faced with the question of which particular DHT system to choose, and whether some are inherently more robust and scalable. Toward developing such a comparative framework, we present the reachable component method (RCM) for analyzing the performance of different DHT routing systems subject to random failures. We apply RCM to five DHT systems and obtain analytical expressions that characterize their routability as a continuous function of system size and node failure probability. An important consequence is that in the large-network limit, the routability of certain DHT systems go to zero for any non-zero probability of node failure. These DHT routing algorithms are therefore unscalable, while some others, including Kademlia, which powers the popular eDonkey P2P system, are found to be scalable.