PEMI: Transparent Performance Enhancements for QUIC

TL;DR

PEMI tackles the challenge that QUIC's end-to-end encryption prevents traditional middlebox optimization. It introduces a fully transparent, best-effort middlebox design that uses flowlet-based inference to measure RTT and detect losses without modifying endpoints, enabling fast retransmissions through controlled, in-network interventions. By adopting a Copa-inspired delay-based congestion control and lightweight CWND enforcement, PEMI achieves significant end-to-end improvements (up to ~2.5x goodput and substantial RTC-frame jitter reductions) while preserving TCP-friendly behavior. The results, validated in Mininet and trace-driven experiments, demonstrate the practical viability of transparent performance enhancements for secure transport protocols, with modest computational overhead and broad compatibility.

Abstract

QUIC, as the transport layer of the next-generation Web stack (HTTP/3), natively provides security and performance improvements over TCP-based stacks. However, since QUIC provides end-to-end encryption for both data and packet headers, in-network assistance like Performance-Enhancing Proxy (PEP) is unavailable for QUIC. To achieve the similar optimization as TCP, some works seek to collaborate endpoints and middleboxes to provide in-network assistance for QUIC. But involving both host and in-network devices increases the difficulty of deployment in the Internet. In this paper, by analyzing the QUIC standard, implementations, and the locality of application traffic, we identify opportunities for transparent middleboxes to measure RTT and infer packet loss for QUIC connections, despite the absence of plaintext ACK information. We then propose PEMI as a concrete system that continuously measures RTT and infers lost packets, enabling fast retransmissions for QUIC. PEMI enables performance enhancement for QUIC in a completely transparent manner, without requiring any explicit cooperation from the endpoints. To keep fairness, PEMI employs a delay-based congestion control and utilizes feedback-based methods to enforce CWND. Extensive evaluation results, including Mininet and trace-driven dynamic experiments, show that PEMI can significantly improve the performance of QUIC. For example, in the Mininet experiments, PEMI increases the goodput of file transfers by up to 2.5$\times$, and reduces the 90th percentile jitter of RTC frames by 20-75%.

Figures (14)

• Figure 1: Sample deployment scenario of PEP. PEP creates a deceptive server and client, communicating with both ends. From the perspective of the end hosts, they are communicating with each other. By leveraging the advantage that sub-links have lower latency than complete end-to-end links, PEP can perform fast retransmissions when packet loss occurs in the network.
• Figure 2: Strawman solution for loss detection.
• Figure 3: Packet transmission time series of a QUIC connection.
• Figure 4: Flowlet measurements from QUIC traffic of Top 100 websites.
• Figure 5: Overview of PEMI.