Accurately estimating available bandwidth helps understand network performance and identify target bitrates for rate-based applications (e.g., video streaming). Traditional “speed test” bandwidth estimation tools often rely on prolonged data transfers, resulting in significant overhead in both time and data transferred. As an alternative, we evaluate using TCP slow start as a lightweight bandwidth probing tool, enhanced to detect the slow start exit point before inducing packet loss. We evaluate this TCP slow start ‘plus’ an enhancement approach (SS+) against three widely used speed test tools over various access links. Results show that the SS+ achieves accuracy comparable to traditional methods, while significantly reducing measurement time and data transmitted.

TCP slow start faces challenges when running over wireless networks due to varying capacities and round-trip times caused by fluctuating channel conditions and cross traffic from competing flows. The TCP Slow start Exit At Right CHoke point (SEARCH) algorithm has been shown to improve slow start over satellite networks, but has not yet been evaluated over more commonly used wireless local area networks (LANs). This paper presents a performance evaluation of SEARCH on a busy campus Wi-Fi LAN, considering a range of network conditions. Our data shows that SEARCH improves TCP’s initial bandwidth-probing behavior in a campus Wi-Fi environment by avoiding premature slow start exits and reducing packet loss compared to traditional TCP and TCP slow start augmented by HyStart.

Frametime spikes and graphical fidelity both matter for the feel of first-person shooter (FPS) games, yet their combined effects are not well understood. This paper examines how graphics settings and frametime spikes during aiming interact with player performance and experience. We developed a custom FPS game with configurable textures, lighting, and visual effects, and induced frametime spikes of 0 ms, 225 ms, or 675 ms during play. Twenty-one participants completed all combinations of graphics and spikes while providing performance data and subjective ratings for visual quality and smoothness. Results show that graphics quality primarily affects perceived visual quality , while frametime spikes primarily reduce perceived smoothness . Performance (i.e., score and accuracy) declines with larger spikes but remains largely unchanged across graphics settings. These findings suggest that spike magnitude, rather than graphics quality, is the dominant factor shaping smoothness and performance, while players still notice higher-quality graphics.

Understanding the effects of latency on interaction is important for building applications, such as computer games, that perform well over a range of latencies. For games that require quick reflexes, such as first-person shooter games, reaction times can be a key determinant for player performance. Unfortunately, measuring and reporting reaction times – and analysis thereof – is not done in many user studies, likely because most easy-to-use tools are only available online and do not provide the raw reaction time data of the participants. To address these shortcomings, this paper presents Reflex an open-source tool for measuring human reaction times. Reflex is implemented in JavaScript, allowing it to be run with only a local Web browser and provides the raw data for subsequent analysis. This paper also presents a data set composed of Reflex data gathered from eight previous user studies, with brief analysis comparing their reaction time results to illustrate Reflex’s use.

Cloud gaming relies upon smooth delivery of frames and low delay for a good player Quality of Experience (QoE). While playout buffering has long been used in traditional streaming systems – e.g., streaming video and VoIP – to smooth out variations in delay and available bandwidth, algorithms for playout buffering for cloud game streams are under-researched. In particular, QoE models for cloud-based game streams differ from those for traditional media, suggesting algorithms that have been widely used and proposed may need to be adjusted for cloud gaming. This paper investigates playout buffer policies on cloud gaming QoE by employing a trace-driven simulation framework that allows for a head-to-head comparison of policies. By integrating established QoE models, our study quantifies how these technical parameters affect perceived gaming quality. Our results reveal that the effectiveness of a buffer policy is highly dependent on the network conditions, with adaptive strategies showing potential benefits in environments with high jitter, while more conservative policies may suffice under stable network conditions.

Frametime spikes can disrupt gameplay in first-person shooter (FPS) games, affecting both performance and player experience. This paper examines how spikes during specific game events impact players. We developed a custom FPS game that maintains a steady 500 frames/s while inducing frametime spikes during weapon reloading, fast mouse movement, or targeting. Thirty-eight (38) participants played the game in a user study, providing both performance data and user-reported visual smoothness. Results show that spikes while targeting lowered accuracy and score, while spikes during reloads and mouse movement did not affect performance but still degraded user experience. These results suggest that both the relative timing and size of frametime spikes matter in FPS gameplay. Per-action models better account for average QoE when spikes happen, showing better fit than models that only consider spike size (independent of action).

The Slow start Exit At Right CHokepoint (SEARCH) algorithm is designed to exit the TCP slow start phase after the flow has reached the link capacity but before packets have been lost. To do this, SEARCH keeps a history of the bytes delivered over a recent time window, aggregated into bins. Unfortunately, this delivery history must be kept per-flow, adding additional memory load for each TCP connection. We address this per-flow memory load by observing that SEARCH only needs the relative number of bytes delivered and propose a bit-shifting technique that dynamically compresses bin values as needed. Our approach is tunable to the memory-use reduction required compared to the delivery precision needed. Evaluation of our approach over a satellite network shows SEARCH bin memory use can be reduced by 50% or even 75% without any significant sacrifice in SEARCH algorithm accuracy. Our approach is generalizable to other network algorithms, too, reducing memory use for algorithms that use sliding windows and historical data tracking.

TCP's slow start phase is particularly inefficient over most wireless networks, especially high-latency, high-bandwidth paths such as satellite networks, often exiting too early or too late (after packet loss). To address this, the Slow start Exit At CHokepoint (SEARCH) algorithm is designed to improve exit decisions during slow start by analyzing delivery trends across sliding RTT-based windows. This paper presents a first implementation of SEARCH in the FreeBSD kernel using FreeBSD's modular congestion control framework. We evaluate our implementation on a testbed with an actual GEO satellite link with similar to 600 ms RTT and 150 Mb/s capacity. Preliminary results show that SEARCH exits slow start more effectively than HyStart and HyStart++, achieving higher throughput and better utilization.

User studies are a cornerstone of human-computer interaction research, including measures of user performance and quality of experience (QoE) – particularly important for games where frame rates and frame timings can impact performance. Unfortunately, commercial games have limited options for customization and do not log player performance data with sufficient detail for use in such studies. This paper introduces Lead Rush, a first-person shooter game designed for conducting user studies on the effects of frame timing and frame rate. Lead Rush is tuned to run at extremely high frame rates and includes hooks to induce frame time "spikes". Researchers can configure Lead Rush’s gameplay, trigger frame time spikes during specific actions, and log player data per game round and per study session. This paper also introduces a dataset from a user study on the effects of frame time spikes on player performance gathered from Lead Rush, and includes gameplay logs with both performance data and QoE results. Some analysis of the dataset is presented to illustrate its use.

Computer games - and computer game players - often drive technology improvements, with graphics cards and monitors pushing the limits of display technologies. High frame rates, in particular, promise to provide lower latencies and smoother game visuals to gamers, especially important for competitive first person shooter (FPS) game players. What is not well-known is to what extent gamers benefit from ultra-high frame rates in terms of player performance and quality of experience. This paper studies the effects of frame rates - especially high frame rates - on FPS game players. A custom FPS game was developed to allow for consistent delivery of frame rates from 7 f/s to 500 f/s, while recording objective (performance) and subjective (smoothness) measures. Analysis of data from a 44-person user study shows player performance (e.g., score) improves sharply from 7+ f/s, but levels out after about 90 f/s. However, users perception benefits over the full range of frame rates studied, rising sharply from 7+ f/s, but continuing to improve through the top 500 f/s.

Latency impacts individual responsiveness and player-versus-player fairness in first-person shooter (FPS) games, degrading the quality of experience (QoE). Time delay applies a fixed latency to players with lower latency to make the game fair, but has the drawback of adding latency regardless of whether players are interacting or not. Adaptive time delay dynamically adds latency only when players interact, improving average responsiveness while preserving fairness. This study assesses QoE for adaptive time delay with latency with a focus on the potential benefits of dynamically adding latency compared to always having a fixed latency for the round. A 38-person user study with a custom FPS game shows degredations to QoE with latency, but less so for adaptive time delay.

Cloud-based game streaming is emerging as a convenient way to play games when clients have a good network connection. However, high-quality game streams need high bitrates and low latencies, a challenge when competing for network capacity with other flows. While some network aspects of cloud-based game streaming have been studied, missing are comparative performance and congestion responses to competing TCP flows. This paper presents results from experiments that measure how three popular commercial cloud-based game streaming systems - Google Stadia, NVidia GeForce Now, and Amazon Luna - respond and then recover to TCP Cubic and TCP BBR flows on a congested network link. Analysis of bitrates, loss rates and round-trip times show the three systems have markedly different responses to the arrival and departure of competing network traffic.

In first-person shooter (FPS) games, the peeker’s advantage is the edge the moving peeker gets when battling a stationary defender at a corner due to network latency. However, confirmation of (the size of) this advantage based on network latency and the distance from the corner has not been studied. This paper assesses the peeker’s advantage via two user studies both using an open-source FPS game extended to support two-player networking and a custom map. Users play as both peeker and defender with 3 different corner distances and 3 different network latencies. Analysis of hits, wins, and time-to-damage shows that the advantage for the peeker is impacted more by the defender’s latency than the peeker’s latency and is lowest when the peeker is nearest the corner. The user study with a tournament setting had quicker and more competitive matches resulting in more combat encounters and closer games than did the traditional user study.

For gamers, high frame rates are important for a smooth visual display and good quality of experience (QoE). However, high frame rates alone are not enough as variations in the frame display times can degrade QoE even as the average frame rate remains high. While the impact of steady frame rates on player QoE is fairly well-studied, the effects of frame rate variation is not. This paper presents a 33-person user study that evaluates the impact of frame rate variation on users playing three different computer games. Analysis of the results shows average frame rate alone is a poor predictor of QoE, and frame rate variation has a significant impact on player QoE. While the standard deviation of frame times is promising as a general predictor for QoE, frame time standard deviation may not be accurate for all individual games. However, 95% frame rate floor -– the bottom 5% of frame rates the player experiences –- appears to be an effective predictor of both QoE overall and for the individual games tested.

TCP slow start begins at a conservative bitrate but quickly ramps up to the available bandwidth. Unfortunately, current TCP implementations can either: 1) exit from slow start prematurely, which is especially detrimental to utilization on satellite links, or 2) exit from slow start too late, causing unnecessary packet loss. We propose a novel technique to exit slow start while avoiding both premature and belated exits. We evaluate our approach over commercial satellite links - long, fat networks that pose challenges to determining the right slow start exit time. Preliminary results show a high success rate for picking appropriate exit points over satellite links, with potentially being applicable to other types of networks, more generally.

While target selection in a 2D space is fairly well-studied, target selection in a 3D space, such as shooting in first-person shooter (FPS) games, is not, nor are the benefits to players for many latency compensation techniques. This paper presents results from a user study that evaluates the impact of latency and latency compensation techniques on 3D target selection via a bespoke FPS shooter. Analysis of the results shows latency degrades player performance (time to select/shoot a target), with subjective opinions on Quality of Experience (QOE) following suit. Individual latency compensation techniques cannot fully overcome the effects of latency but combined techniques can, letting players perform and feel as if there is no network latency. We derive a basic analytic model for the distribution of the player selection times which can be part of a simulation of a full-range of FPS games.

Cloud-based game streaming has the disadvantage of added latency from the thin client to the cloud-based server and back, decreasing player performance and degrading their experience. Attribute scaling can make the game eas-ier, potentially exactly counteracting the difficulty added by the latency. We incorporate attribute scaling models into two different games, deploy them on a commercial cloud-based game streaming system and evaluate their efficacy by measuring impact on player performance and Quality of Experience (QoE). Analysis through a user study shows that our compensation methods improve player performance and may improve QoE compared to no latency compensation.