  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.
