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QUIC is not Quick Enough over Fast Internet

Xumiao Zhang, Shuowei Jin, Yi He, Ahmad Hassan, Z. Morley Mao, Feng Qian, Zhi-Li Zhang

TL;DR

This work systematically evaluates QUIC performance over high-speed networks and finds that UDP+QUIC+HTTP/3 often underperforms compared with TCP+TLS+HTTP/2 as bandwidth increases, with gaps up to 45.2% in real-browser tests and measurable impacts on video streaming and page loading. Through controlled experiments, packet trace analysis, and OS/Chromium profiling, the authors identify the primary bottleneck as receiver-side processing caused by excessive data packets and user-space ACKs, rather than sender-side transmission. They propose practical mitigations including UDP GRO on the receiver, QUIC-friendly offloading, delayed ACKs, and multi-core receive strategies, while noting implementation and hardware heterogeneity challenges. The study contributes a detailed, reproducible measurement methodology and provides data and source code to guide cross-layer optimizations for QUIC and upper-layer protocols in next-generation networks.

Abstract

QUIC is expected to be a game-changer in improving web application performance. In this paper, we conduct a systematic examination of QUIC's performance over high-speed networks. We find that over fast Internet, the UDP+QUIC+HTTP/3 stack suffers a data rate reduction of up to 45.2% compared to the TCP+TLS+HTTP/2 counterpart. Moreover, the performance gap between QUIC and HTTP/2 grows as the underlying bandwidth increases. We observe this issue on lightweight data transfer clients and major web browsers (Chrome, Edge, Firefox, Opera), on different hosts (desktop, mobile), and over diverse networks (wired broadband, cellular). It affects not only file transfers, but also various applications such as video streaming (up to 9.8% video bitrate reduction) and web browsing. Through rigorous packet trace analysis and kernel- and user-space profiling, we identify the root cause to be high receiver-side processing overhead, in particular, excessive data packets and QUIC's user-space ACKs. We make concrete recommendations for mitigating the observed performance issues.

QUIC is not Quick Enough over Fast Internet

TL;DR

This work systematically evaluates QUIC performance over high-speed networks and finds that UDP+QUIC+HTTP/3 often underperforms compared with TCP+TLS+HTTP/2 as bandwidth increases, with gaps up to 45.2% in real-browser tests and measurable impacts on video streaming and page loading. Through controlled experiments, packet trace analysis, and OS/Chromium profiling, the authors identify the primary bottleneck as receiver-side processing caused by excessive data packets and user-space ACKs, rather than sender-side transmission. They propose practical mitigations including UDP GRO on the receiver, QUIC-friendly offloading, delayed ACKs, and multi-core receive strategies, while noting implementation and hardware heterogeneity challenges. The study contributes a detailed, reproducible measurement methodology and provides data and source code to guide cross-layer optimizations for QUIC and upper-layer protocols in next-generation networks.

Abstract

QUIC is expected to be a game-changer in improving web application performance. In this paper, we conduct a systematic examination of QUIC's performance over high-speed networks. We find that over fast Internet, the UDP+QUIC+HTTP/3 stack suffers a data rate reduction of up to 45.2% compared to the TCP+TLS+HTTP/2 counterpart. Moreover, the performance gap between QUIC and HTTP/2 grows as the underlying bandwidth increases. We observe this issue on lightweight data transfer clients and major web browsers (Chrome, Edge, Firefox, Opera), on different hosts (desktop, mobile), and over diverse networks (wired broadband, cellular). It affects not only file transfers, but also various applications such as video streaming (up to 9.8% video bitrate reduction) and web browsing. Through rigorous packet trace analysis and kernel- and user-space profiling, we identify the root cause to be high receiver-side processing overhead, in particular, excessive data packets and QUIC's user-space ACKs. We make concrete recommendations for mitigating the observed performance issues.
Paper Structure (16 sections, 12 figures, 4 tables)

This paper contains 16 sections, 12 figures, 4 tables.

Table of Contents

  1. Introduction
  2. Background and Motivation
  3. QUIC Transport Performance
  4. Methodology
  5. File Download on Lightweight Clients
  6. File Download on Real Browsers
  7. Application Study
  8. Video Streaming
  9. Web Page Loading
  10. Root Cause Analysis
  11. Eliminating Non-contributing Factors
  12. Evidence from Packet Trace Analyses
  13. Root Causes via OS/Chromium Profiling
  14. Recommendations for Mitigation
  15. Related Work
  16. ...and 1 more sections

Figures (12)

  • Figure 1: Throughput of lightweight clients during file download.
  • Figure 2: CPU usage of lightweight clients.
  • Figure 3: Throughput and CPU usage of cURL and quic_client during file download under limited bandwidth.
  • Figure 4: Throughput of the Chrome browser during file download.
  • Figure 5: CPU usage of the Chrome browser.
  • ...and 7 more figures