Video Conferencing and Flow-Rate Fairness: A First Look at Zoom and the Impact of Flow-Queuing AQM

Abstract

Congestion control is essential for the stability of the Internet and the corresponding algorithms are commonly evaluated for interoperability based on flow-rate fairness. In contrast, video conferencing software such as Zoom uses custom congestion control algorithms whose fairness behavior is mostly unknown. Aggravatingly, video conferencing has recently seen a drastic increase in use -partly caused by the COVID-19 pandemic -and could hence negatively affect how available Internet resources are shared. In this paper, we thus investigate the flow-rate fairness of video conferencing congestion control at the example of Zoom and influences of deploying AQM. We find that Zoom is slow to react to bandwidth changes and uses two to three times the bandwidth of TCP in low-bandwidth scenarios. Moreover, also when competing with delay aware congestion control such as BBR, we see high queuing delays. AQM reduces these queuing delays and can equalize the bandwidth use when used with flow-queuing. However, it then introduces high packet loss for Zoom, leaving the question how delay and loss affect Zoom's QoE. We hence show a preliminary user study in the appendix which indicates that the QoE is at least not improved and should be studied further.

Measuring the Performance and Network Utilization of Popular Video Conferencing Applications

“…In this work, we study the efficacy of the VCA congestion control in the case of transient interruptions and background applications. A recent study by Sander et al evaluates Zoom's congestion control along these dimensions [24]. Our work observes similar results for Zoom and also analyses more VCAs, including their fairness to each other and other popular internet applications, namely YouTube (QUIC-based) and Netflix (TCP-based).…”

Can You See Me Now? A Measurement Study of Zoom, Webex, and Meet

“…Given the prevalent multi-CDN strategies [9] and differentiated product offerings, user's QoE can change under different subscription plans or any special license arrangements. For example, Zoom is known to allow users with a university license to connect to AWS in Europe [34], which we do not observe with its free-tier/paid subscription plans. In case of Webex, we confirm that, with a paid subscription, its clients in US-west and Europe can stream from geographically close-by Webex servers (with RTTs < 20 ms).…”

“…Despite the prevalence of commercial videoconferencing systems [36], no previous work has directly compared them with respect to their infrastructures and end-user QoE, which is the main objective of this paper. The recent works by [34] and [29] investigate the network utilization and bandwidth sharing behavior of existing commercial videoconferencing systems based on controlled network conditions and client settings. Several works propose generic solutions to improve videoconferencing.…”