Large-Scale Measurement of NAT Traversal for the Decentralized Web: A Case Study of DCUtR in IPFS

TL;DR

This study provides a large-scale empirical analysis of the DCUtR NAT traversal protocol in IPFS, challenging assumptions about UDP's superiority and offering insights for improving decentralized P2P connectivity.

Contribution

First large-scale measurement of a fully decentralized NAT traversal protocol in production IPFS, providing benchmarks and insights for future protocol improvements.

Findings

70% success rate for NAT hole-punching given prerequisites

TCP and QUIC have statistically indistinguishable success rates (~70%)

97.6% of successful connections are established on the first attempt

Abstract

The promise of decentralized peer-to-peer (P2P) systems is fundamentally gated by the challenge of Network Address Translation (NAT) traversal, with existing solutions often reintroducing the very centralization they seek to avoid. This paper presents the first large-scale measurement study of a fully decentralized NAT traversal protocol, Direct Connection Upgrade through Relay (DCUtR), within the production libp2p-based InterPlanetary File System (IPFS) network. Drawing on over 4.4 million traversal attempts from 85,000+ distinct networks across 167 countries, we provide an empirical analysis of modern P2P connectivity. We establish a conditional success rate of $70\% \pm 7.1\%$ for the hole-punching stage, given that prerequisite relay reservation and public address discovery succeed, providing a crucial new benchmark for the field. Critically, we empirically challenge the long-held belief of UDP's superiority for NAT traversal, demonstrating that DCUtR's high-precision, RTT-based synchronization yields statistically indistinguishable success rates for both TCP and QUIC ($\sim70\%$). Our analysis further validates the protocol's design for permissionless environments by showing that success is independent of relay characteristics and that the mechanism is highly efficient, with $97.6\%$ of successful connections established on the first attempt. Building on this analysis, we propose a concrete roadmap of protocol enhancements aimed at achieving universal connectivity and contribute our complete dataset to foster further research in this domain.