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.

翻译：本文对QUIC即时确认（一种符合标准的方法）在常见CDN部署中减少QUIC连接建立等待时间的性能进行了详细分析。为深入理解其性能特性的根本原因，我们结合数值分析与通过QUIC互操作性测试运行器对八种QUIC实现的仿真实验。我们的实验全面涵盖了数据包丢失与非丢失场景、不同的往返时延以及TLS证书大小。为阐明实际部署中的即时确认机制，我们对100万个热门域名进行了主动测量。结果显示，几乎所有由Cloudflare控制的域名均采用了即时确认技术，该技术确实提升了性能。然而，我们也发现，在某些网络条件下即时确认可能导致不必要的重传或更长的等待时间，这提示我们需要关注即时确认技术在未来应用中可能存在的缺陷。