Networked Virtual Environments Research Articles

Providing survivability for virtual networks against substrate network failure

Network virtualization has been regarded as a core attribute of the Future Internet. In a network virtualization environment (NVE), multiple heterogeneous virtual networks can coexist on a shared substrate network. Thus, a substrate network failure may affect multiple virtual networks. In this case, it is increasingly critical to provide survivability for the virtual networks against the substrate network failures. Previous research focused on mechanisms that ensure the resilience of the virtual network. However, the resource efficiency is still important to make the mapping scheme practical. In this paper, we study the survivable virtual network embedding mechanisms against substrate link and node failure from the perspective of improving the resource efficiency. For substrate link survivability, we propose a load-balancing and re-configuration strategy to improve the acceptance ratio and bandwidth utilization ratio. For substrate node survivability, we develop a minimum cost heuristic based on a divided network model and a backup resource cost model, which can both satisfy the location constraints of virtual node and increase the sharing degree of the backup resources. Simulations are conducted to evaluate the performance of the solutions. The proposed load balancing and re-configuration strategy for substrate link survivability outperforms other approaches in terms of acceptance ratio and bandwidth utilization ratio. And the proposed minimum cost heuristic for substrate node survivability gets a good performance in term of acceptance ratio.

The safety assessment system based on virtual networked environment for evaluation on the hazards from human errors during decommissioning of nuclear facilities

This paper is intended to suggest a system for evaluation on the hazards from human errors during decommissioning of nuclear facilities. The system was developed under virtual networked environment. The innovative features are real-time changing direction of workers in a scenario and real-time measuring personal exposure dose and collective exposure dose. The system will be expected to be utilized as a training tool for improving familiarization of a workplace and for preventing workers from accidents.

Sprite tree: an efficient image-based representation for networked virtual environments

In this paper we present a pipeline for automatic analysis of neuronal morphology: from detection, modeling to digital reconstruction. First, we present an automatic, unsupervised object detection framework using stochastic marked point process. It extracts connected neuronal networks by fitting special configuration of marked objects to the centreline of the neurite branches in the image volume giving us position, local width and orientation information. Semantic modeling of neuronal morphology in terms of critical nodes like bifurcations and terminals, generates various geometric and morphology descriptors such as branching index, branching angles, total neurite length, internodal lengths for statistical inference on characteristic neuronal features. From the detected branches we reconstruct neuronal tree morphology using robust and efficient numerical fast marching methods. We capture a mathematical model abstracting out the relevant position, shape and connectivity information about neuronal branches from the microscopy data into connected minimum spanning trees. Such digital reconstruction is represented in standard SWC format, prevalent for archiving, sharing, and further analysis in the neuroimaging community. Our proposed pipeline outperforms state of the art methods in tracing accuracy and minimizes the subjective variability in reconstruction, inherent to semi-automatic methods.

UFalloc: Towards Utility Max-min Fairness of Bandwidth Allocation for Applications in Datacenter Networks

Providing fair bandwidth allocation for applications is becoming increasingly compelling in cloud datacenters, as different applications compete for the shared datacenter network resources. While existing solutions mainly provide bandwidth guarantees for virtual machines (VMs) or tenants with the aim of achieving the VM-level or tenant-level fairness of bandwidth allocation, scant attention has been paid to providing bandwidth guarantees for applications to achieve the fairness of application performance (utility). In this paper, we introduce a rigorous definition of application-level utility max-min fairness, which guides us to develop a non-linear model to investigate the relationship between the utility fairness and bandwidth allocation for applications. Based on such a model, we further arbitrate the intrinsic tradeoff between the network bandwidth utilization and utility fairness of application bandwidth allocation, using a tunable fairness relaxation factor. To improve the bandwidth utilization while maintaining the strict utility fairness of bandwidth allocation, we design UFalloc, an application-level Utility max-min Fair bandwidth allocation strategy in datacenter networks. With extensive experiments using OpenFlow in Mininet virtual network environment, we demonstrate that UFalloc can achieve high utilization of network bandwidth while maintaining the utility max-min fair share of bandwidth allocation with a certain degree of fairness relaxation, yet with an acceptable computational overhead.

Copiar-colar e remix: o que a escola tem a ver com isso?

O conceito de Novos Letramentos, referendado por Lankshear e Knobel, se constitui por meio de uma nova mentalidade envolvendo o uso das Novas Tecnologias de Informacao e Comunicacao. Tal conceito abarca praticas de letramentos digitais como o remix , que e a capacidade de recortar e “misturar” diversos modos como escrita, sons, imagem estatica ou em movimento e recria-los a partir dessa mistura. Tais praticas tem se popularizado, principalmente entre os mais jovens, em funcao de dois fatores: (i) o uso de ferramentas digitais capazes de manipular os novos textos de carater multissemiotico/multimodal da contemporaneidade que circulam em ambientes virtuais da rede e em diversas midias; (ii) da ressignificacao de velhas praticas como o copiar-colar envolvendo, agora, o contexto do mundo digital. Com base nessa perspectiva, o objetivo deste trabalho e analisar as praticas de letramentos digitais de um jovem na criacao de templates e paginas para a internet e, particularmente, para uma rede social. As analises sao feitas a partir de diSessa, para quem o letramento se constitui com base em tres elementos: genero, nicho social e forma representacional. Alem disso, trazemos Bazerman em suas consideracoes sobre como a escola tem lidado com a questao do plagio a partir da popularizacao do uso da internet. A discussao teorica envolvendo Bazerman e a analise das praticas letradas desse jovem evidenciam a enorme distância entre os letramentos valorizados pela escola e os (novos) letramentos que sao praticados pelos jovens fora dela, e, assim, a discussao sinaliza a necessidade de a escola (i) (re)considerar a nocao de remix , visto que a ideia de copiar e colar esta imersa em uma nova mentalidade por parte dos jovens no uso das ferramentas digitais e do proprio conteudo que e disponibilizado na internet; (ii) incorporar esses letramentos digitais, que ja acontecem em ambientes digitais de rede, as praticas de letramento escolares. Palavras-chave: novos letramentos, copiar-colar, remix .

Uplink Blocking Probabilities in Priority-Based Cellular CDMA Networks with Finite Source Population

Fast proliferation of mobile Internet and high-demand mobile applications necessitates the introduction of different priority classes in next-generation cellular networks. This is especially crucial for efficient use of radio resources in the heterogeneous and virtualized network environments. Despite the fact that many analytical tools have been proposed for capacity and radio resource modelling in cellular networks, only a few of them explicitly incorporate priorities among services. We propose a novel analytical model to analyse the performance of a priority-based cellular CDMA system with finite source population. When the cell load is above a certain level, low-priority calls may be blocked to preserve the quality of service of high-priority calls. The proposed model leads to an efficient closed-form solution that enables fast and very accurate calculation of resource occupancy of the CDMA system and call blocking probabilities, for different services and many priority classes. To achieve them, the system is modelled as a continuous-time Markov chain. We evaluate the accuracy of the proposed analytical model by means of computer simulations and find that the introduced approximation errors are negligible.

A Dynamic Platform for Developing 3D Facial Avatars in a Networked Virtual Environment

Avatar facial expression and animation in 3D collaborative virtual environment (CVE) systems are reconstructed through a complex manipulation of muscles, bones, and wrinkles in 3D space. The need for a fast and easy reconstruction approach has emerged in the recent years due to its application in various domains: 3D disaster management, virtual shopping, and military training. In this work we proposed a new script language based on atomic parametric action to easily produce real-time facial animation. To minimize use of the game engine, we introduced script-based component where the user introduces simple short script fragments to feed the engine with a new animation on the fly. During runtime, when an embedded animation is required, an xml file is created and injected into the game engine without stopping or restarting the engine. The resulting animation method preserves the real-time performance because the modification occurs not through the modification of the 3D code that describes the CVE and its objects but rather through modification of the action scenario that rules when an animation happens or might happen in that specific situation.

Energy-aware node and link reconfiguration for virtualized network environments

Energy consumption in information and communications technology (ICT) accounts for a large portion of the total energy consumed in industrial countries, which is rapidly increasing. Virtualized network environments (VNEs) have recently emerged as a solution in this technology to address the challenges of future Internet. VNEs also play a fundamental role toward virtualizing data centers. Consequently, it is essential to develop novel techniques for reducing the energy consumption of VNEs. In this paper, we discuss multiple energy-saving solutions that locally optimize the node and link energy consumption of VNEs during the off-peak period by reconfiguring the mapping of already allocated virtual nodes and links. The proposed reconfigurations enable the providers to adjust the level of the reconfiguration and accordingly control possible traffic disruptions. An integer linear program (ILP) is formulated for each solution. Because the defined ILPs are NP-hard, a novel heuristic algorithm is also proposed. The proposed energy-saving methods are evaluated over random VNE scenarios. The results confirm that the solutions save notable amounts of energy in physical nodes and links during the off-peak period.

Vulnerabilities and solutions for isolation in FlowVisor-based virtual network environments

In a virtualized environment, different virtual networks can operate over the same physical infrastructure. Each virtual network has its own protocols and share the available resources, thus highlighting the need of resource isolation mechanisms. Investigating the isolation mechanisms provided by FlowVisor, we have discovered vulnerabilities previously unknown regarding addressing space isolation. We show that, in the presence of a malicious controller, FlowVisor’s isolation can be broken allowing different attacks. This paper addresses these vulnerabilities by proposing an Action Slicing mechanism, that allows FlowVisor to limit which actions can be used by each virtual network controller, thus extending the virtual network definition. Our experimental results show that using the proposed Action Slicing mechanism can effectively neutralize the discovered vulnerabilities.

Approximate resolution of asynchronous conflicts among sequential collaborations in dynamic virtual environments

AbstractAsynchronous collaboration for a networked virtual environment (NVE) has emerged as a promising area in collaborative computer‐aided design applications. The concept of asynchronous collaboration is a sequential collaboration of temporal processes in an NVE where the participants are not required to be present at the time of the collaboration. Conflicts in asynchronous collaboration occur because the preceding task of a participant can influence the output of the ensuing task of another participant. The conflicted tasks must be modified manually. However, it requires considerable time and effort to resolve conflicts in a sequential collaboration. In this paper, we present an asynchronous collaborative framework that converts the conflict states of the shared objects into approximately resolved states. We develop a novel approximate resolution algorithm using a task‐based modeling mechanism to resolve the asynchronous conflicts with their corresponding tasks. Moreover, we propose a visual relation editor for convenient management. The participants can set flexible relations among shared objects using the proposed visual editor. The proposed approximate resolution approach can significantly reduce the average resolution time and the number of required manual task resolutions in a virtual environment compared to a manual resolution approach. Copyright © 2015 John Wiley & Sons, Ltd.

Efficient 3-D Scene Prefetching From Learning User Access Patterns

Rendering large-scale 3-D scenes on a thin client is attracting increasing attention with the development of the mobile Internet. Efficient scene prefetching to provide timely data with a limited cache is one of the most critical issues for remote 3-D data scheduling in networked virtual environment applications. Existing prefetching schemes predict the future positions of each individual user based on user traces. In this paper, we investigate scene content sequences accessed by various users instead of user viewpoint traces and propose a user access pattern-based 3-D scene prefetching scheme. We make a relationship graph-based clustering to partition history user access sequences into several clusters and choose representative sequences from among these clusters as user access patterns. Then, these user access patterns are prioritized by their popularity and users’ personal preference. Based on these access patterns, the proposed prefetching scheme predicts the scene contents that will most likely be visited in the future and delivers them to the client in advance. The experiment results demonstrate that our user access pattern-based prefetching approach achieves a high hit ratio and outperforms the prevailing prefetching schemes in terms of access latency and cache capacity.

An automated approach to dependability evaluation of virtual networks

Network virtualization has been pointed as a promising approach to solve Internet’s current ossification. A major challenge is the mapping of virtual networks (VNs) onto the substrate network due to its NP-hard nature, and, thus, several heuristics have been proposed aiming to achieve efficient allocations. However, the existing approaches only focus on performance, and dependability issues are usually neglected. Dependability involves metrics such as reliability and availability, which directly impact the quality of service, and a limitation is the absence of mechanisms for estimating dependability metrics in virtual networks. This paper proposes an automated approach for estimating dependability metrics in virtual network environments and a mapping algorithm based on GRASP metaheuristic. The approach is based on stochastic Petri nets (SPN) and reliability block diagrams (RBD), and a tool is also presented for automating model generation and evaluation. Experimental results demonstrate the feasibility of the proposed technique, as well as the trade-off between VN’s availability and cost.

Protection Management for Guaranteed User-Driven Virtual Circuit Services in Dynamic Multi-domain Environments: Design Issues and Challenges

Fault management of virtualized network environments using user-driven network provisioning systems (NPSs) is crucial for guaranteeing seamless virtual network services irrespective of physical infrastructure impairment. The network service interface (NSI) of the Open Grid Forum reflects the need for a common standard management API for the reservation and provisioning of user-driven virtual circuits (VCs) across global networks. NSI-based NPSs (that is, network service agents) can be used to compose user-driven VCs for mission-critical applications in a dynamic multi-domain. In this article, we first attempt to outline the design issues and challenges faced when attempting to provide mission-critical applications using dynamic VCs with a protection that is both user-driven and trustworthy in a dynamic multi-domain environment, to motivate work in this area of research. We also survey representative works that address inter-domain VC protection and qualitatively evaluate them and current NSI against the issues and challenges.

OnDemand Virtual Radio Resource Allocation for Wireless Access

In future virtual network (VNet) environments, where heterogeneous networks will coexist and new business roles and models are expected, VNets cooperation for radio resource management is one of the key issues in order to achieve an efficient integration of different wireless technologies, while providing the required quality of service. In this paper, an algorithm for Virtual Radio Resource Allocation (VRRA), called OnDemandVRRA, in multiple and heterogeneous virtual networks environment is proposed and discussed. OnDemandVRRA manages the radio resources allocation to the VNets in order to satisfy the VNet contracted capacity. The algorithm has been assessed for two different Virtual scenarios by comparison with a Standard one, in which several network operators have their own networks, each being shared among several mobile virtual network operators. It is shown that the application of OnDemandVRRA to virtualise the wireless access allows achieving better performance from a cluster of several base stations of different radio access technologies, supporting the provision of the contracted capacity for guaranteed VNets, i.e., VNets with a minimum contracted capacity. Globally, it is observed that Virtual scenarios perform better than the Standard one, as the cluster serving data rate may increase by approximately 46 %, if minimum and reference values for the VNet's contracted capacity have been set. Moreover, in this case, end-users performing best-effort services are served with an average data rate approximately three times higher than in other scenarios, where the reference data rate for the VNet providing these services is not set.

Analysis of Slow Read DoS Attack and Countermeasures on Web servers

The ideas and techniques of DoS (Denial of Service) and DDoS (Distributed DoS) Attack strategies become more effective and more complex. In this paper, we focus on a Slow Read DoS Attack which is one of the sophisticated DoS attack techniques. This technique prolongs time to read the response from the Web server, although an attacker sends a legitimate HTTP request. When an attacker sends many such legitimate requests, he can keep many open connections to Web server and eventually cause DoS situation. In this paper, we analyze the effectiveness of Slow Read DoS Attack using the virtual network environment. As the result, we can find that Slow Read DoS Attack by a single attacker can be prevented by adequate security settings of Web server and applying countermeasure such as ModSecurity. However, from the analysis of Slow Read DoS Attack technique, we can also find that these countermeasures are not effective against distributed Slow Read DoS Attack (Slow Read Distributed DoS Attack) which is proposed in this paper.

网络虚拟化环境下的业务聚类方法

网络虚拟化环境下的业务聚类方法

High-Level Portable Programming Language for Optimized Memory Use of Network Processors

Network processors (NPs) are widely used for programmable and high-performance networks; however, the programs for NPs are less portable, the number of NP program developers is small, and the development cost is high. To solve these problems, this paper proposes an open, high-level, and portable programming language called “Phonepl”, which is independent from vendor-specific proprietary hardware and software but can be translated into an NP program with high performance especially in the memory use. A common NP hardware feature is that a whole packet is stored in DRAM, but the header is cached in SRAM. Phonepl has a hardware-independent abstraction of this feature so that it allows programmers mostly unconscious of this hardware feature. To implement the abstraction, four representations of packet data type that cover all the packet operations (including substring, concatenation, input, and output) are introduced. Phonepl have been implemented on Octeon NPs used in plug-ins for a network-virtualization environment called the VNode Infrastructure, and several packet-handling programs were evaluated. As for the evaluation result, the conversion throughput is close to the wire rate, i.e., 10 Gbps, and no packet loss (by cache miss) occurs when the packet size is 256 bytes or larger.

Toward an Approach to Product Design Process Modeling and Conflict Resolution for Collaborative Virtual Environment

According to engineering and technical staffs' requirements in inter-multidisciplinary domains collaborative product design, design process modeling method and conflict resolution algorithm are both put forward. The actual needs are deeply analyzed for multidisciplinary collaborative product design. By means of a third-party data file conversion format-.3D, a collaborative design mode and its framework structure are respectively presented based on a product sharing view model. For the design schemes of multiple users' collaborative activities process, a conflict resolution algorithm of design requests is also implemented. Finally, based on the J2EE architecture, a lightweight virtual network environment is developed to support collaborative design process, and its application validation work is also discussed. The feasibility and effectiveness method and architecture proposed have been also testified reasonable.

Design of an Efficient Method for Identifying Virtual Machines Compatible with Service Chain in a Virtual Network Environment

With advancements in network technologies, network virtualization has been proposed to efficiently provide a large number of services and flexible management by utilizing limited resources over existing networks as much as possible. Network virtualization has been proposed as a new paradigm for networks, as it simplifies complicated network configurations for convenient maintenance through the maximum utilization of limited network resources. However, problems have arisen due to network virtualization, such as how to assign real network components that are compatible with virtual network components over a large number of virtual machines existing in a network. In particular, the servicechaining concept—where a network flow only passes through needed services—has been newly introduced by combining the recently highlighted Software-Defined Network with a virtualization concept called Network Function Virtualization. As a result, studies on which virtual machines are selected and how to connect them have increased ever more. Accordingly, this paper aims to identify virtual machines that are compatible with service chaining in a virtual network environment where virtual machines are dispersed, and it proposes a method of how to create a path by connecting virtual machines.

Adversarial topology discovery in network virtualization environments: a threat for ISPs?

Network virtualization is a new Internet paradigm which allows multiple virtual networks (VNets) to share the resources of a given physical infrastructure. The virtualization of entire networks is the natural next step after the virtualization of nodes and links. While the problem of how to embed a VNet (“guest network”) on a given resource network (“host network”) is algorithmically well-understood, much less is known about the security implications of this new technology. This paper introduces a new model to reason about one particular security threat: the leakage of information about the physical infrastructure—often a business secret. We initiate the study of this new problem and introduce the notion of request complexity which describes the number of VNet requests needed to fully disclose the substrate topology. We derive lower bounds and present algorithms achieving an asymptotically optimal request complexity for important graph classes such as trees, cactus graphs (complexity $$O(n)$$ ) as well as arbitrary graphs (complexity $$O(n^2)$$ ). Moreover, a general motif-based topology discovery framework is described which exploits the poset structure of the VNet embedding relation.