Maha Abdallah

One-phase commit: does it make sense?

Although widely used in distributed transactional systems, the so-called Two-Phase Commit (2PC) protocol introduces a substantial delay in transaction processing, even in the absence of failures. This has led several researchers to look for alternative commit protocols that minimize the time cost associated with coordination messages and forced log writes in 2PC. In particular, variations of a One-Phase Commit (1PC) protocol have recently been proposed. Although efficient, 1PC is however rarely considered in practice because of the strong assumptions it requires from the distributed transactional system. The aim of the paper is to better identify and understand those assumptions. Through a careful look into the intrinsic characteristics of 1PC, we dissect the assumptions underlying it and we present simple techniques that minimize them. We believe that these techniques constitute a first step towards a serious reconsideration of 1PC in the transactional world.

VoroGame: A Hybrid P2P Architecture for Massively Multiplayer Games

Peer-to-peer (P2P) architectures have recently become very popular in massively multiplayer games (MMGs). While P2P gaming offers high scalability compared to client/server architectures, it introduces several major issues related to data distribution and game state consistency. In this paper, we report our initial version of VoroGame, a P2P architecture for MMGs that addresses these issues by combining a structured P2P overlay based on a distributed hash table (DHT) for data distribution, with a Voronoi diagram used for virtual game world decomposition and semantic overlay support. The resulting hybrid architecture enables a fully distributed management of data and state information, and ensures efficient dissemination of game state updates to relevant peers.

A spatial publish subscribe overlay for massively multiuser virtual environments

Peer-to-peer (P2P) architectures have become popular for designing scalable virtual environments (VEs) in recent years. However, one question that remains is whether a single overlay can be flexible enough to support different types of VEs. We present S-VON, a P2P overlay that attempts this goal by providing spatial publish/subscribe (SPS) services. Besides flexibility, S-VON also aims to be practical and efficient by utilizing super-peers and considering the physical topology (i.e., network distance) to reduce latencies. Our simulations show that super-peers provide a unique design space where both bandwidth usage and latencies can be effectively reduced, such that even a crowded Second Life region can be hosted with residential ADSL.

A Survey of Peer-To-Peer Overlay Approaches for Networked Virtual Environments

This paper identifies and analyzes the key design approaches that have been proposed over the last decade to construct a peer-to-peer (P2P) networked virtual environment (NVE) systems. We discuss each approach, their advantages and drawbacks, and examine several representative P2P-based NVE systems based on the presented approaches, thus providing the background and literature review of P2P NVEs.

Peer-to-peer visualization of very large 3D landscape and city models using MPEG-4

The recent availability of broadband Internet access and web-based visualization techniques is paving the way for a large scale use of 3D landscape and city models for a great variety of professional and mass market services. To make such services appealing to a large audience, these 3D models must reach a sufficient level of realism and accuracy. Many solutions are now available to automatically generate 3D models of huge urban environments. Geographic Information System (GIS) databases (i.e. terrain elevation grids, ortho photographs, buildings footprint and height) provide a good basis for generating such models at affordable cost with minimum human intervention. However, the growing size of the transmitted data will favour streaming over download-and- play. Moreover, the new market for virtual worlds is likely to be soon demanding in interoperability. The goal of this paper is to show how solutions based on hierarchical LOD models and view-dependent progressive streaming can efficiently be implemented using the MPEG-4 AFX standard in peer-to-peer networks architectures, solving both streaming and interoperability issues.

GROUP: Dual-Overlay State Management for P2P NVE

Peer-to-peer (P2P) architectures have recently become a popular design choice to build scalable Networked Virtual Environments (NVEs). While P2P architectures offer better scalability than server-based architectures, efficient distribution and management of avatar and object states remains a highly challenging issue. In this paper, we propose GROUP, a fully-distributed P2P architecture for NVEs that addresses this issue by combining a structured P2P overlay, used for object state management, with a Voronoi-based overlay, used for avatar state and group membership management. The resulting dual overlay architecture enables efficient and fully distributed management of state updates for P2P-based NVEs.

Toward Delay-Efficient Game-Aware Data Centers for Cloud Gaming

Gaming on demand is an emerging service that has recently started to garner prominence in the gaming industry. Cloud-based video games provide affordable, flexible, and high-performance solutions for end-users with constrained computing resources and enables them to play high-end graphic games on low-end thin clients. Despite its advantages, cloud gamings Quality of Experience (QoE) suffers from high and varying end-to-end delay. Since the significant part of computational processing, including game rendering and video compression, is performed in data centers, controlling the transfer of information within the cloud has an important impact on the quality of cloud gaming services. In this article, a novel method for minimizing the end-to-end latency within a cloud gaming data center is proposed. We formulate an optimization problem for reducing delay, and propose a Lagrangian Relaxation (LR) time-efficient heuristic algorithm as a practical solution. Simulation results indicate that the heuristic method can provide close-to-optimal solutions. Also, the proposed model reduces end-to-end delay and delay variation by almost 11% and 13.5%, respectively, and outperforms the existing server-centric and network-centric models. As a byproduct, our proposed method also achieves better fairness among multiple competing players by almost 45%, on average, in comparison with existing methods.

SDN-based game-aware network management for cloud gaming

Cloud based video games bring new opportunities to the gaming industry, and enable end-users to play high-end graphic games on any low-end device without high performance hardware requirements. As the major computational parts of game processing, including users input processing, rendering and encoding the game scene, and video streaming are performed in data centers, data centers play a key role in providing high quality games to end-users. Software Defined Networking (SDN) enables the management and control of communication inside the data center in a centralized fashion, such that it can be employed as a means to optimize flow distribution. In this paper, we present a Linear Programing (LP) optimization-based method for optimally assigning game servers to gaming sessions and selecting the best communication path within a cloud gaming datacenter. Our optimization model considers the type of requested games, current server loads, and current path delays. Our experimental results show that the proposed model minimizes the average delay of all players within a datacenter by 9.6%, and outperforms the existing server-centric and network-centric models.

Introduction to the Special Section on Visual Computing in the Cloud: Cloud Gaming and Virtualization

Cloud gaming, the newest entry in the online gaming world, leverages the well-known concept of cloud computing to provide real-time gaming services to players. The idea in cloud gaming is to capture the game events from players and transmit them to the cloud, process those events and run the game logic in the cloud, render the game scene as video in the cloud, and stream that video to the players. The advantage is that as long as the client can display video, which pretty much all smartphones, tablets, game consoles, desktops, laptops, and mobile devices today do, the user can play the game without installing it locally, and without needing to have a machine with high-grade 3-D graphics rendering and powerful computing hardware and software. This makes cloud gaming accessible to a huge market of mass consumers. While some variations of cloud gaming systems stream 3-D graphics, in addition to or instead of video, the great majority of cloud gaming implementations are video based. Using the well-known concept of software as a service, cloud gaming is also sometimes referred to as gaming as a service, which is already available as commercial products, such as Sony’s PlayStation Now, Ubitus’s GameNow, G-Cluster, Crytek’s GFACE, PlayGiga, and LiquidSky, to name a few. There are also many efforts concentrating specifically on the underlying technology behind cloud gaming, such as NVIDIA’s Grid, OTOY, CiiNow, Kalydo, and GamingAnywhere [4], the latter being the only open source and free technology. Microsoft is also exploring cloud gaming technologies, with recent successes such as its Kahawai project [1].

A flexible connectivity architecture for avatar management in P2P virtual environments

The present paper addresses the efficient management of avatar states in P2P virtual environments (VEs) by building on our previously proposed Relaxed Triangulation (RT) overlay, designed to accommodate the dynamic nature of VEs by drastically reducing the maintenance cost inherent to the well-known Delaunay construct. Given that our RT overlay no longer supports greedy routing, we propose in this paper to complement our RT overlay with a message routing algorithm that guarantees message delivery on top of RT.