Toward Scalable Docker-Based Emulations of Blockchain Networks

Blockchain, like any other technology, needs a strong testing methodology to support its evolution. Setting up meaningful blockchain tests is a notoriously complex task for several reasons: software is complex, large number of nodes are involved, network is non ideal, etc. Developers usually adopts small virtual laboratories or costly real devnets, based on real software. Researchers usually prefer simulations of a large number of nodes, based on simplified models. In this paper, we aim to obtain the advantages of both approaches, i.e., performing large, realistic, unexpensive, and flexible experiments, using real blockchain software within a virtual environment. To do that, we tackle the challenge of running large blockchain networks in a single physical machine, leveraging Linux and Docker. We analyze a number of problems that arise when large blockchain networks are emulated and we provide technical solutions for all of them. Finally, we describe our experience of emulating a fairly large blockchain network, comprising more than 3000 containers, for research purposes

Design and Evaluation of a Virtual Experimental Environment for Distributed Systems

International audienceBetween simulation and experiments on real-scale testbeds, the combined use of emulation and virtualization provide a useful alternative for performing experiments on distributed systems such as clusters, grids, cloud computing or P2P systems. In this paper, we present Distem, a software tool to build distributed virtual experimental environments. Using an homogenenous set of nodes, Distem emulates a platform composed of heterogeneous nodes (in terms of number and performance of CPU cores), connected to a virtual network described using a realistic topology model. Distem relies on LXC, a low-overhead container-based virtualization solution, to achieve scalability and enable experiments with thousands of virtual nodes. Distem provides a set of user interfaces to accomodate different needs (command-line for interactive use, Ruby and REST APIs), is freely available and well documented. After a detailed description of Distem, we perform an experimental evaluation of several of its features.Entre la simulation et l'expérimentation sur des plates-formes réelles, l'usage combiné de l'émulation et de la virtualisation fournit une alternative utile pour réaliser des expériences sur des systèmes distribués tels que les clusters, grilles, le Cloud ou les systèmes P2P. Dans cet article, nous présentons Distem, un logiciel permettant de construire des environnements expérimentaux distribués virtuels. À partir d'un ensemble homogène de noeuds, Distem émule une plate-forme composée de noeuds hétérogènes (en termes de nombre et de performance de leurs coeurs CPU), connectés à un réseau virtuel décrit à partir d'un modèle de topologies réaliste. Distem se base sur LXC, une solution de virtualisation légère à base de conteneurs, pour obtenir des propriétés de passage à l'échelle satisfaisantes et permettre des expériences avec des milliers de noeuds virtuels. Distem fournit plusieurs interfaces utilisateurs permettant de s'adapter à différents besoins (ligne de commande pour l'usage interactif, Ruby, API REST), est librement disponible et bien documenté. Après une description détaillée de Distem, cet article présente une validation expérimentale de plusieurs de ses fonctionnalités

Une Plate-forme d'Emulation Légère pour Etudier les Systèmes Pair-à-Pair

National audienceLes méthodes actuellement les plus utilisées pour étudier les systèmes pair-à-pair (modélisation, simulation, et exécution sur des systèmes réels) montrent souvent des limites sur les plans du passage à l'échelle et du réalisme. Cet article présente P2PLab, une plate-forme pour l'étude et l'évaluation des systèmes pair-à-pair, qui combine l'émulation (utilisation de l'application réelle à étudier à l'intérieur d'un environnement synthétique) et la virtualisation. Après la présentation des caractéristiques principales de P2PLab (émulation réseau distribuée, virtualisation légère), nous montrons son utilité lors de l'étude du système de diffusion de fichiers BitTorrent, notamment en comparant deux implantations différentes de ce protocole complexe

Network environment for testing peer-to-peer streaming applications

Peer-to-Peer (P2P) streaming applications are an emerging trend in content distribution. A reliable network environment was needed to test their capabilities and performance limits, which this thesis focused on. Furthermore, some experimental tests in the environment were performed with an application implemented in the Department of Communications Engineering (DCE) at Tampere University of Technology. For practical reasons, the testing environment was assembled in a teaching laboratory at DCE premises. The environment was built using a centralized architecture, where a Linux emulation node, WANemulator, generates realistic packet losses, delays, and jitters to the network. After an extensive literature survey an extension to the Iproute2’s Tc utility, NetEm, was chosen to be responsible of the network link emulation at the WANemulator. The peers are run inside VirtualBox images, which are used at the Linux computers to keep the laboratory still suitable for teaching purposes. In addition to the network emulation, Linux traffic controlling mechanisms were used both at the WANemulator and VirtualBox’s virtual machines to limit the traffic rates of the peers. When used together, emulation and rate limitation resemble to the statistical behaviour of the Internet quite closely. Virtualization overhead limited the maximum number of Virtual Machines (VMs) at each laboratory computer into two. Also, a peculiar feature in VirtualBox’s bridge implementation reduced the network capabilities of the VMs. However, the bottleneck in the environment is the centralized architecture, where all of the traffic is routed through the WANemulator. The environment was tested reliable with the chosen streamed content and 160 peers, but by tuning the parameters in WANemulator bigger overlays might be achievable. In addition, a distributed emulation should be possible with the environment, but it was not tested. The results from the experimental tests performed with the P2P streaming application proved the application to be functional in an environment that has mobile network conditions. The designed network environment is tested to work reliably, it enables reasonable scalability and provides better possibility to emulate the networking characteristics of the Internet, when compared to an ordinary local area network environment. /Kir1

Lightweight emulation to study peer-to-peer systems

The current methods used to test and study peer-topeer systems (namely modeling, simulation, or execution on real testbeds) often show limits regarding scalability, realism and accuracy. This paper describes and evaluates P2PLab, our framework to study peer-to-peer systems by combining emulation (use of the real studied application within a configured synthetic environment) and virtualization. P2PLab is scalable (it uses a distributed network model) and has good virtualization characteristics (many virtual nodes can be executed on the same physical node by using process-level virtualization). Experiments with the BitTorrent file-sharing system complete this paper and demonstrate the usefulness of this platform. 1