PeerSwap: A Peer-Sampler with Randomness Guarantees

TL;DR

PeerSwap is a peer-sampling protocol with provable randomness guarantees that efficiently scales with network size, ensuring quick and uniform peer sampling in decentralized systems.

Contribution

This paper introduces PeerSwap, a novel peer-sampling protocol with theoretical guarantees on randomness and execution time, modeled as an interchange process.

Findings

PeerSwap maintains fixed communication graph structure.

Execution time can be polylogarithmic in network size.

Numerical evaluations confirm quick uniform sampling up to 32768 peers.

Abstract

The ability of a peer-to-peer (P2P) system to effectively host decentralized applications often relies on the availability of a peer-sampling service, which provides each participant with a random sample of other peers. Despite the practical effectiveness of existing peer samplers, their ability to produce random samples within a reasonable time frame remains poorly understood from a theoretical standpoint. This paper contributes to bridging this gap by introducing PeerSwap, a peer-sampling protocol with provable randomness guarantees. We establish execution time bounds for PeerSwap, demonstrating its ability to scale effectively with the network size. We prove that PeerSwap maintains the fixed structure of the communication graph while allowing sequential peer position swaps within this graph. We do so by showing that PeerSwap is a specific instance of an interchange process, a renowned model for particle movement analysis. Leveraging this mapping, we derive execution time bounds, expressed as a function of the network size N. Depending on the network structure, this time can be as low as a polylogarithmic function of N, highlighting the efficiency of PeerSwap. We implement PeerSwap and conduct numerical evaluations using regular graphs with varying connectivity and containing up to 32768 (2^15) peers. Our evaluation demonstrates that PeerSwap quickly provides peers with uniform random samples of other peers.