ReACKed QUICer: Measuring the Performance of Instant Acknowledgments in QUIC Handshakes

TL;DR

This paper analyzes the performance of QUIC instant ACK, revealing its benefits in reducing delays and its potential drawbacks like unnecessary retransmissions, through extensive experiments and real-world measurements.

Contribution

It provides a comprehensive performance evaluation of QUIC instant ACK, combining numerical analysis, emulation, and active measurements to understand its benefits and limitations.

Findings

Instant ACK improves performance in Cloudflare deployments.

Instant ACK can cause unnecessary retransmissions under certain conditions.

Performance varies with network conditions and TLS certificate sizes.

Abstract

In this paper, we present a detailed performance analysis of QUIC instant ACK, a standard-compliant approach to reduce waiting times during the QUIC connection setup in common CDN deployments. To understand the root causes of the performance properties, we combine numerical analysis and the emulation of eight QUIC implementations using the QUIC Interop Runner. Our experiments comprehensively cover packet loss and non-loss scenarios, different round trip times, and TLS certificate sizes. To clarify instant ACK deployments in the wild, we conduct active measurements of 1M popular domain names. For almost all domain names under control of Cloudflare, Cloudflare uses instant ACK, which in fact improves performance. We also find, however, that instant ACK may lead to unnecessary retransmissions or longer waiting times under some network conditions, raising awareness of drawbacks of instant ACK in the future.