An experimental evaluation of server performance in Networked Virtual Environments

Several works in the literature have recently addressed the study of different Networked Virtual Environments (NVE) due to their increasing popularity and widespread use in fields ranging from entertainment to e-Health. Open Wonderland is one of these NVEs which has been the subject of several studies mainly focused on the client side. This paper aims to cover the server-side performance issues to provide complementary results that can be useful for properly sizing Open Wonderland systems according to the number of expected users. An experimental testbed is used, which provides real data that shows that CPU and outgoing bandwidth are the most critical parameters when the number of clients increase.Ministerio de Ciencia e Innovación PROCUR@-IPT-2011-1038-900000Ministerio de Ciencia e Innovación TEC2009-10639-C04-0

An Unobtrusive Method for Tracking Network Latency in Online Games

Online games are a very important class of distributed interactive applications. Their success is heavily dependant on the level of consistency that can be maintained between participants communicating in the virtual world. Achieving a high level of consistency usually involves the transmission of a large amount of network traffic. However, if the underlying network connecting participants is unable to process this traffic, then network latency will increase, which will in turn negatively impact on consistency. Many schemes exist which attempt to reduce network traffic, and thus reduce the effect of network latency on the interactive application. However, applications that employ these schemes tend to do so with little knowledge of the underlying network conditions, and assume a worst-case scenario of limited bandwidth. Such an assumption can actually cause these latency reduction schemes to perform sub-optimally, and ironically introduce more inconsistency than they reduce. Hence, it is important that online game applications become aware of network conditions, such as available bandwidth. Existing methods of estimating bandwidth operate by analysing trends in one-way latency, and require that extra data be transmitted between nodes in order to capture the latency trends. Such an approach does not suit online games, as the extra data requirements could increase network latency, and affect the ability of the application to scale to multiple participants. To deal with this issue, this paper proposes a method by which online games can unobtrusively track one-way network latency. This method requires no time-stamping information to be transmitted between participants and operates using data already being transmitted as part of the online game application, meaning that its impact on the network is minimal. NS2 simulations demonstrate that the trends collected by this method can be used to estimate bandwidth under certain conditions

OpenGL|D - An Alternative Approach to Multi-user Architecture

© Springer-Verlag GmbH Germany, part of Springer Nature 2018. Synchronising state between multiple connected clients can be a challenging task. However, the need to carry this out is becoming much greater as a larger number of software packages are becoming collaborative across a network. Online multiplayer games in particular are already extremely popular but the synchronisation methods and architecture have largely remained the same. OpenGL|Distributed, presented here, aims to provide not only an alternative to this architecture allowing for a greatly simplified development pipeline, but also the opportunity for a number of additional features and design patterns. The architecture provided by OpenGL|D is such that no state information needs to be transferred between clients. Instead, the OpenGL API has been utilised as a platform agnostic protocol. This means that graphical calls can be streamed to each client rather than relying on manual synchronisation of application domain specific data. Initial test results are discussed, including performance evaluation using data from a number of small prototypes developed within a constrained 48-h timeframe. These results are compared and evaluated against a more traditional approach to network multiplayer by id Software’s QuakeWorld client. It should be noted that this article is an extended version of the work we published in the proceedings of the Cyberworlds 2017 conference [1]

Network traffic characterisation, analysis, modelling and simulation for networked virtual environments

Networked virtual environment (NVE) refers to a distributed software system where a simulation, also known as virtual world, is shared over a data network between several users that can interact with each other and the simulation in real-time. NVE systems are omnipresent in the present globally interconnected world, from entertainment industry, where they are one of the foundations for many video games, to pervasive games that focus on e-learning, e-training or social studies. From this relevance derives the interest in better understanding the nature and internal dynamics of the network tra c that vertebrates these systems, useful in elds such as network infrastructure optimisation or the study of Quality of Service and Quality of Experience related to NVE-based services. The goal of the present work is to deepen into this understanding of NVE network tra c by helping to build network tra c models that accurately describe it and can be used as foundations for tools to assist in some of the research elds enumerated before. First contribution of the present work is a formal characterisation for NVE systems, which provides a tool to determine which systems can be considered as NVE. Based on this characterisation it has been possible to identify numerous systems, such as several video games, that qualify as NVE and have an important associated literature focused on network tra c analysis. The next contribution has been the study of this existing literature from a NVE perspective and the proposal of an analysis pipeline, a structured collection of processes and techniques to de ne microscale network models for NVE tra c. This analysis pipeline has been tested and validated against a study case focused on Open Wonderland (OWL), a framework to build NVE systems of di erent purpose. The analysis pipeline helped to de ned network models from experimental OWL tra c and assessed on their accuracy from a statistical perspective. The last contribution has been the design and implementation of simulation tools based on the above OWL models and the network simulation framework ns-3. The purpose of these simulations was to con rm the validity of the OWL models and the analysis pipeline, as well as providing potential tools to support studies related to NVE network tra c. As a result of this nal contribution, it has been proposed to exploit the parallelisation potential of these simulations through High Throughput Computing techniques and tools, aimed to coordinate massively parallel computing workloads over distributed resources

Mobile three-dimensional city maps

Maps are visual representations of environments and the objects within, depicting their spatial relations. They are mainly used in navigation, where they act as external information sources, supporting observation and decision making processes. Map design, or the art-science of cartography, has led to simplification of the environment, where the naturally three-dimensional environment has been abstracted to a two-dimensional representation, populated with simple geometrical shapes and symbols. However, abstract representation requires a map reading ability. Modern technology has reached the level where maps can be expressed in digital form, having selectable, scalable, browsable and updatable content. Maps may no longer even be limited to two dimensions, nor to an abstract form. When a real world based virtual environment is created, a 3D map is born. Given a realistic representation, would the user no longer need to interpret the map, and be able to navigate in an inherently intuitive manner? To answer this question, one needs a mobile test platform. But can a 3D map, a resource hungry real virtual environment, exist on such resource limited devices? This dissertation approaches the technical challenges posed by mobile 3D maps in a constructive manner, identifying the problems, developing solutions and providing answers by creating a functional system. The case focuses on urban environments. First, optimization methods for rendering large, static 3D city models are researched and a solution provided by combining visibility culling, level-of-detail management and out-of-core rendering, suited for mobile 3D maps. Then, the potential of mobile networking is addressed, developing efficient and scalable methods for progressive content downloading and dynamic entity management. Finally, a 3D navigation interface is developed for mobile devices, and the research validated with measurements and field experiments. It is found that near realistic mobile 3D city maps can exist in current mobile phones, and the rendering rates are excellent in 3D hardware enabled devices. Such 3D maps can also be transferred and rendered on-the-fly sufficiently fast for navigation use over cellular networks. Real world entities such as pedestrians or public transportation can be tracked and presented in a scalable manner. Mobile 3D maps are useful for navigation, but their usability depends highly on interaction methods - the potentially intuitive representation does not imply, for example, faster navigation than with a professional 2D street map. In addition, the physical interface limits the usability

Hydra: loosely coupling the graphics pipeline to facilitate digital preservation.

It can be argued that software can be seen as a form of art and digital heritage and yet it rarely enjoys the same efforts afforded to it compared to physical counterparts. There are many reasons for this, such as the increasing costs of maintenance or the reducing amount of expertise in the specific aging technology. Maintaining software and ensuring that it continues to work on current hardware and operating systems is known as digital preservation. There are many ways in which we can attempt to preserve digital software and one of the most effective ones is by using emulation to simulate the obsolete hardware. However, for games and other entertainment media, this technique is not always effective due to a requirement on specific hardware, such as an accelerated GPU in order to reach an acceptable performance for the user. It is often difficult to emulate a GPU and, as such, a different approach often needs to be taken, which reduces the flexibility and portability of the emulation software. Hydra is a new approach to accessing the native hardware from within an emulated environment which allows for a much simpler emulator to be developed and maintained and yet also offers the potential of accessing other types of hardware without needing to modify the emulation software itself. Hydra is designed to be platform agnostic in that not only is it possible to integrate with existing emulators but also be immediately usable from within guest operating systems, ranging from legacy platforms such as MS-DOS, through to modern platforms such as the PlayStation 4 (Orbis OS, a FreeBSD derivative), through to more exotic platforms such as Plan 9 from Bell Laboratories. It can do this because it does not rely on a complex emulator-specific virtual driver stack. This PhD thesis provides the research undertaken for Hydra, including the motivation behind it, the specific problems it was designed to solve and how it can be implemented in a platform agnostic manner. Hydra’s performance is analysed to ascertain the suitability of the output to cater for, specifically, a wide variety of platforms that it can run on in a satisfactory manner within less powerful or emulated environments. A performance analysis study is conducted to ensure that the technology provides an acceptable solution to accessing preserved titles. This study concluded with results showing that Hydra offers a greater performance than software rendering, especially within emulated environments. A bandwidth comparison between Hydra and VNC was undertaken to ascertain the use of the technology as a streaming medium. The results concluded that under specific conditions, Hydra performed better than VNC by streaming at a higher resolution and consuming less bandwidth. Hydra is also utilised in a number of engineering tasks relating to preservation of software. The experiences of using Hydra in this way are discussed, including any difficulties encountered. Lastly, a conclusion is made and any future work is identified

Traffic modelling for fast action network games

A significant share of today’s Internet traffic is generated by network gaming. This kind of traffic is interesting in regard to it’s market potential as well as to it’s real time requirements on the network. For the consideration of game traffic in network dimensioning, traffic models are required that allow to generate a characteristic load for analytical or simulative performance evaluation of networks. In this paper the fast action multiplayer game „Counter Strike “ is evaluated based on one month of Internet traffic traces and traffic models for client and server are presented. The paper concludes with remarks on QoS metrics for an adequate assessment of performance evaluation results. 1