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Video Conferencing Applications (VCAs) employ real-time congestion (rate) control algorithms on top of UDP. In this paper, we take an in-depth look at the congestion control behavior of four proprietary VCAs: Zoom, Microsoft Teams, Google Meet, and Cisco Webex. We compare their startup phases, bandwidth probing behaviors, and reactions to packet delays and drops. We uncover previously-unknown bandwidth estimation strategies, and tradeoffs in how quickly they react to available bandwidth changes. Our study is based on over 130 hours of VCA traffic data collected under diverse network conditions and two buffer sizes, and annotated with sending rate, buffer occupancy, packet drop, and several user Quality of Experience (QoE) metrics. Our dataset is publicly available to support further research in understanding VCA performance. 

Immersive virtual reality (VR) experiences require transmission and rendering of large-scale 3D content, often represented as point clouds or polygon meshes. Unfortunately, existing networked VR systems often fail to fully exploit the flexibility of VR data representations. To address this problem, we propose a cross-layer design that elevates a network data unit to a usable rendering unit for VR applications. Our aim is to bridge the gap between networks and applications in order to enhance visual quality, especially over constrained and variable networks. Our approach, Rendering Unit that is Network-aware (RUN), with two variants, RUN-Packet and RUN-Hybrid, includes mechanisms to effectively utilize network data units when encoding, transmitting, decoding, and rendering. Specifically, we develop additive detail refinement mechanisms and address streaming challenges such as head-of-line (HoL) blocking. We prototype our system in Unity 3D and evaluate it using synthetic network environments and real network traces. Our results with both static and dynamic point clouds demonstrate that RUN significantly reduces stalls and delivers smoother frame updates, enhancing visual quality. 

Wi-Fi is an integral part of today's Internet infrastructure, enabling a diverse range of applications and services. Prior approaches to Wi-Fi resource allocation optimized Quality of Service (QoS) metrics, which often do not accurately reflect the user's Quality of Experience (QoE). To address the gap between QoS and QoE, we introduce Maestro, an adaptive method that formulates the Wi-Fi resource allocation problem as a partially observable Markov decision process (PO-MDP) to maximize the overall system QoE and QoE fairness. Maestro estimates QoE without using any application or client data; instead, it treats them as black boxes and leverages temporal dependencies in network telemetry data. Maestro dynamically adjusts policies to handle different classes of applications and variable network conditions. Additionally, Maestro uses a simulation environment for practical training. We evaluate Maestro in an enterprise-level Wi-Fi testbed with a variety of applications, and find that Maestro achieves up to 25× and 78% improvement in QoE and fairness, respectively, compared to the widely-deployed Wi-Fi Multimedia (WMM) policy. Compared to the state-of-the-art learning approach QFlow, Maestro increases QoE by up to 69%. Unlike QFlow which requires modifications to clients, we demonstrate that Maestro improves QoE of popular over-the-top services with unseen traffic without control over clients or servers. 

EXtended Reality (XR) is rapidly gaining popularity. XR systems are often networked, in the sense that one or more client devices such as headsets or glasses fetch data from one or more servers over a (typically wireless last-link) network. A crucial step to advancing the design of XR systems is realizing reproducible performance evaluation based on a set of representative benchmark test scenarios. In this article, we define what constitutes an XR benchmark, including XR environment representations, user views and actions, system capabilities and conditions, and evaluation metrics for user Quality of Experience (QoE) and for system resource consumption. We believe that community involvement in creating such benchmarks can significantly accelerate the development of usable and cost-effective XR technology. 

The increasing popularity of video streaming and conferencing services have altered the nature of Internet traffic. In this paper, we take a first step toward quantifying the impact of this changing nature of traffic on the Quality of Experience (QoE) of popular video streaming and conferencing applications. We first analyze the traffic characteristics of these applications and of backbone links, and show how simple multipath routing may adversely impact application QoE. To mitigate this problem, we propose a new routing path selection approach, inspired by the TCP timeout computation algorithm, that uses both the average and variation of path load. Preliminary results show that this approach improves application QoE by on average 14% and packet latency by 11% for video streaming and conferencing applications, respectively. 

Emerging multimedia applications often use a wireless LAN (Wi-Fi) infrastructure to stream content. These Wi-Fi deployments vary vastly in terms of their system configurations. In this paper, we take a step toward characterizing the Quality of Experience (QoE) of volumetric video streaming over an enterprise-grade Wi-Fi network to: (i) understand the impact of Wi-Fi control parameters on user QoE, (ii) analyze the relation between Quality of Service (QoS) metrics of Wi-Fi networks and application QoE, and (iii) compare the QoE of volumetric video streaming to traditional 2D video applications. We find that Wi-Fi configuration parameters such as channel width, radio interface, access category, and priority queues are important for optimizing Wi-Fi networks for streaming immersive videos.