Technical Report: Implementation of Single Packet Number Space in Multi-Path QUIC

TL;DR

This paper compares single packet number space and multiple packet number space implementations of multi-path QUIC through experiments, providing insights into their performance implications to aid deployment decisions.

Contribution

It provides the first experimental comparison of SPNS and MPNS in multi-path QUIC, informing standardization and implementation choices.

Findings

SPNS shows lower latency in certain scenarios.

MPNS offers better packet loss recovery.

Performance varies based on network conditions.

Abstract

Over the past few of years, we have witnessed increasing interests in the use cases of multi-path QUIC from both industry and academia. For example, Alibaba deployed XLINK, a QoE-driven multi-path QUIC solution, in Taobao short video and showed benefits in both reduced tail latency and video re-buffering. For the time being, the multi-path QUIC protocol is in the process of standardization at the IETF QUIC working group, with the draft recently updated to version 02. The focus of the draft is to provide basic guidance on the implementation so that we can encourage more exploration, testing, and finally, an accelerated adoption of this technology. However, draft-02 has brought up an open issue on whether the multi-path QUIC should be implemented using single packet number space (SPNS) or multiple packet number space (MPNS), as in the current draft, both options co-exist. Knowing that one cannot draw a solid conclusion without experiments, we implement both SPNS and MPNS at Alibaba and measured their performance. The goal is to help the community better understand the implication, and we hope this report can be a useful resource for engineers and researchers who are interested in deploying multi-path QUIC.