Virtual Layer Research Articles

Building resilience in virtual digital response networks: a case study

The evolution of technology is creating a more complex, connected society of interdependent networks and processes. As connectivity increases, so does the concentration of value. This increases the consequence of failure and the scale, scope and complexity of potential risks causing these systems to fail. These systems are made resilient by making the physical and virtual networks resilient in isolation and intersection. Yet existing resilience practices fail to address the complexities of virtual networks and their dynamics with the physical environment, specifically the requirements of physical infrastructure networks to enable resilient virtual networks and vice versa. This paper aims to address this gap through a simulated case study of resilience development within and between a physical network and a virtual online network. The networked operational resilience framework is applied to an emergency services network partnered with a digital response network (DRN). DRNs are virtual networks of crowdsourced volunteers that respond to the virtual layer of crisis. Building situational awareness to aid decision-making, they have become an essential tool of crisis response. Findings address the context of virtual online networks in isolation and partnership, enabling infrastructure requirements, the risk environment and resilience capability and development.

Catching Escapers

As the Industry 4.0 or Internet of Things (IoT) era begins, security plays a key role in the Industry Internet of Things (IIoT) due to various threats, which include escape or Distributed Denial of Service (DDoS) attackers in the virtualization layer and vulnerability exploiters in the device layer. A successful cross-VM escape attack in the virtualization layer combined with cross-layer penetration in the device layer, which we define as an Advanced Persistent Escaper (APE), poses a great threat. Therefore, the development of detection and rejection methods for APEs across multiple layers in IIoT is an open issue. To the best of our knowledge, less effective methods are established, especially for vulnerability exploitation in the virtualization layer and backdoor leverage in the device layer. On the basis of this, we propose Escaper Cops (EscaperCOP), a detection method for cross-VM escapers in the virtualization layer and cross-layer penetrators in the device layer. In particular, a new detection method for guest-to-host escapers is proposed for the virtualization layer. Finally, a novel encryption method based on Identity-based Broadcast Encryption (IBBE) is proposed to protect the critical components in EscaperCOP, detection library, and control command library. To verify our method, experimental tests are performed for a large number of APEs in an IIoT framework. The test results have demonstrated the proposed method is effective with an acceptable level of detection ratio.

Investigation of epidemic spreading process on multiplex networks by incorporating fatal properties

Numerous efforts have been devoted to investigating the network activities and dynamics of isolated networks. Nevertheless, in practice, most complex networks might be interconnected with each other (due to the existence of common components) and exhibit layered properties while the connections on different layers represent various relationships. These types of networks are characterized as multiplex networks. A two-layered multiplex network model (usually composed of a virtual layer sustaining unaware-aware-unaware (UAU) dynamics and a physical one supporting susceptible-infected-recovered-dead (SIRD) process) is presented to investigate the spreading property of fatal epidemics in this manuscript. Due to the incorporation of the virtual layer, the recovered and dead individuals seem to play different roles in affecting the epidemic spreading process. In details, the corresponding nodes on the virtual layer for the recovered individuals are capable of transmitting information to other individuals, while the corresponding nodes for the dead individuals (which are to be eliminated) on the virtual layer should be removed as well. With the coupled UAU-SIRD model, the relationships between the focused variables and parameters of the epidemic are studied thoroughly. As indicated by the results, the range of affected individuals will be reduced by a large amount with the incorporation of virtual layers. Furthermore, the effects of recovery time on the epidemic spreading process are also investigated aiming to consider various physical conditions. Theoretical analyses are also derived for scenarios with and without required time periods for recovery which validates the reducing effects of incorporating virtual layers on the epidemic spreading process.

Can I/O Variability Be Reduced on QoS-Less HPC Storage Systems?

For a production high-performance computing (HPC) system, where storage devices are shared between multiple applications and managed in a best effort manner, I/O contention is often a major problem. In this paper, we propose a balanced messaging-based re-routing in conjunction with throttling at the middleware level. This work tackles two key challenges that have not been fully resolved in the past: whether I/O variability can be reduced on a QoS-less HPC storage system, and how to design a runtime scheduling system that can scale up to a large amount of cores. The proposed scheme uses a two-level messaging system to re-route I/O requests to a less congested storage location so that write performance is improved, while limiting the impact on read by throttling re-routing. An analytical model is derived to guide the setup of optimal throttling factor. We thoroughly analyze the virtual messaging layer overhead and explore whether the in-transit buffering is effective in managing I/O variability. Contrary to the intuition, in-transit buffer cannot completely solve the problem. It can reduce the absolute variability but not the relative variability. The proposed scheme is verified against a synthetic benchmark as well as being used by production applications.

Dispersion of passive tracers from long-range HF radar systems along the east coast of Korea

We have conducted a virtual surface layer dispersion experiment using the long-range High Frequency radar (HFR) measurements off the east coast of Korea, and investigated the spreading characteristics of the surface waters in the vicinity of two cities, YoungDuk and UlJin for three days of experiments utilizing with random flight model (Markovian stochastic model). The diffusion coefficient was estimated as (Kx , Ky ) = (192, 251) m 2 /s with zonal and meridional dispersions ( σ² u, σ²υ ) = (0.0013, 0.017) m/s and turbulence time scales (Tu , Tv ) = (4, 4) hours derived from exponential fitting of lagged autocorrelation of difference between the HFR-derived and surface drifter-derived currents. During the experiment period, the centroid of the spatial particle distribution moved northward 80 km from the initial position following the East Korea Warm Current (EKWC) and its area became more than 500 times than the initial area. The trajectory and distribution of the surface particles are dependent on the EKWC and diffusion coefficient. Long-term and real-time continuous monitoring system of HFR needs to be combined into national system to improve search and rescue (SAR), and prevent coastal disasters (e.g., oil spill, marine litter) for risk management.

Security Aware Virtual Network Embedding Algorithm Using Information Entropy TOPSIS

Network virtualization is an effective manner to address the ossification issue of Internet architecture. Virtual network embedding is one of the most critical techniques in network virtualization environments. Several security problems about virtual network embedding are introduced due to the fact that virtual network embedding adds a virtual layer into the internet architecture. In this paper, we proposed an approach for security aware virtual network embedding called SA-VNE to address the security problems in virtual network embedding process. Firstly, we use the information entropy TOPSIS method to rank the importance of substrate nodes with an aim to choose the most appropriate substrate node for accommodating the virtual node. Secondly, we use the shortest path algorithm to perform the link mapping process. Simulation results demonstrated that our proposed SA-VNE algorithm behaves better that those of state-of-the-art existing security aware virtual network embedding algorithms in terms of the long-term average revenue, the long-term average VN acceptance ratio, the long-term average revenue to cost ratio and the running time.

Amazon Elastic Compute Cloud (EC2) versus In-House HPC Platform: A Cost Analysis

While High Performance Computing (HPC) centers continuously evolve to provide more computing power to their users, we observe a wish for the convergence between Cloud Computing (CC) and High Performance Computing (HPC) platforms, with the commercial hope to see Cloud Computing (CC) infrastructures to eventually replace in-house facilities. If we exclude the performance point of view where many previous studies highlight a non-negligible overhead induced by the virtualization layer at the heart of every Cloud middleware when running a HPC workload, the question of the real cost-effectiveness is often left aside with the intuition that, most probably, the instances offered by the Cloud providers are competitive from a cost point of view. In this article, we wanted to assert (or infirm) this intuition by analyzing what composes the Total Cost of Ownership (TCO) of an in-house HPC facility operated internally since 2007. This Total Cost of Ownership (TCO) model is then used to compare with the induced cost that would have been required to run the same platform (and the same workload) over a competitive Cloud IaaS offer. Our approach to address this price comparison is three-fold. First we propose a theoretical price-performance model based on the study of the actual Cloud instances proposed by one of the major Cloud IaaS actors: Amazon Elastic Compute Cloud (EC2). Then, based on the HPC facility TCO analysis we propose a hourly price comparison between our in-house cluster and the equivalent EC2 instances. Finally, based on the experimental benchmarking on the local cluster and on the Cloud instances we propose an update of the former theoretical price model to reflect the real system performance. The results obtained advocate in general for the acquisition of an in-house HPC facility, which balances the common intuition in favor of Cloud Computing platforms, would they be provided by the reference Cloud provider worldwide.

Contact Resistance Model and Thermal Stability Analysis of Bolt Structure

This paper introduces a contact resistance model of bolt structures based on virtual material method. The main idea of the model is to interpose a virtual layer between the overlapped bus bar and define properties including equivalent resistivity and equivalent modulus of elasticity to describe the dynamic characteristics of the distributed contact resistance. The determining method of these properties is introduced, and the validity of the model is demonstrated by comparing the calculated contact resistance with the measured results. The model is further applied to the coupled electromagnetic–stress–thermal finite-element calculation to analyze the thermal stability of the bolt structure. The temperature rise process inside the bolt structure is studied, and the strengthening effect of the electrodynamic force on the thermal field is revealed. Besides, the influences of contact loosening and oxidation are also researched with the method.

An Access Control Model for Preventing Virtual Machine Hopping Attack

As a new type of service computing model, cloud computing provides various services through the Internet. Virtual machine (VM) hopping is a security issue often encountered in the virtualization layer. Once it occurs, it directly affects the reliability of the entire computing platform. Therefore, we have thoroughly studied the virtual machine hopping attack. In addition, we designed the access control model PVMH (Prevent VM hopping) to prevent VM hopping attacks based on the BLP model and the Biba model. Finally, we implemented the model on the Xen platform. The experiments demonstrate that our PVMH module succeeds in preventing VM hopping attack with acceptable loss to virtual machine performance.

Comparative Studies of AlGaAs/InGaAs Enhancement/Depletion-Mode High Electron Mobility Transistors with Virtual Channel Layers by Hybrid Gate Recesses Approaches

Unlike the conventional GaAs- and InP-based enhancement/depletion-mode (E/D-mode) transistors, the improved gate characteristics of the AlGaAs/InGaAs E-mode high electron mobility transistors (HEMTs) by way of hybrid gate recesses to remove the n-AlAs/i-GaAs/n-AlGaAs virtual channel layers upon 2DEG channels are demonstrated. As compared to the D-mode device (sample A), the gate reverse currents are effectively reduced by 45 and 102 times for the E-mode devices with additional gate recess time of 24 s (sample B) and 30 s (sample C) to remove part of the virtual channel layers, respectively. Under gate forward bias, the hybrid gate recesses also enable the gate turn-on voltages to increase. Furthermore, the threshold voltages of –1.25, 0.09, and 0.22 V are observed in the samples A, B, and C, respectively. The maximum transconductances of 187.3, 209.2, and 243.4 mS/mm and saturation current density of 482.8, 410.6, and 347.4 mA/mm are obtained in the samples A, B, and C, respectively.

Isolation in cloud computing infrastructures: new security challenges

Cloud computing infrastructures share hardware resources among different clients, leveraging virtualization to multiplex physical resources among several self-contained execution environments such as virtual machines or Linux containers. Isolation is a core security challenge for such a computing paradigm. It may be threatened by side-channels, created due to the sharing of physical resources like processor caches, or by mechanisms implemented in the virtualization layer. Side-channel attacks (SCAs) exploit and use such leaky channels to obtain sensitive data such as kernel information. This paper aims to clarify the nature of this threat for cloud infrastructures. Current SCAs are performed locally and exploit isolation challenges of virtualized environments to retrieve sensitive information. This paper also clarifies the concept of distributed side-channel attack (DSCA). We explore how such attacks can threaten isolation of any virtualized environments such as cloud computing infrastructures. Finally, we study a set of different applicable countermeasures for attack mitigation in cloud infrastructures.

Simulation of three-dimensional bubble formation and interaction using the high-density-ratio lattice Boltzmann method

The growth and departure of bubbles from an orifice and their interactions is a common phenomenon. In this paper, a multiphase flow model based on the lattice Boltzmann method is constructed to study this process, with an improved interface capture method being adopted to deal with the high density ratio between liquid and gas. A virtual layer is added outside the computational domain to handle the boundary condition at the orifice. The processes of bubble formation and interaction are well simulated by the model, and the results agree well with those of theoretical calculations for single-bubble formation and departure diameter and period. Bubble formation is controlled by the inertial force of the gas, buoyancy, surface tension, and the viscous force of the liquid. The inertial force of the gas and buoyancy promote bubble growth and departure, respectively, while the surface tension controls bubble deformation and the viscous force affects the necking process. Increases in both the orifice size and the gas outflow velocity can enlarge the departure diameter of the bubble, but the orifice size plays a more important role here. Both of these two parameters have obvious effects on the departure period. For the interaction of bubbles growing from orifices with the same or different sizes, different coalescence categories are distinguished according to the stage of coalescence, and the characteristics of the coalescence process are considered in terms of their dependence on surface tension, viscous force, and buoyancy. Finally, the departure diameter and departure period of coalesced bubbles are studied under the different coalescence conditions.

Comparative Studies of AlGaAs/InGaAs Enhancement/Depletion-Mode High Electron Mobility Transistors with Virtual Channel Layers by Hybrid Gate Recesses Approaches -=SUP=-*-=/SUP=-

AbstractUnlike the conventional GaAs- and InP-based enhancement/depletion-mode ( E / D -mode) transistors, the improved gate characteristics of the AlGaAs/InGaAs E -mode high electron mobility transistors (HEMTs) by way of hybrid gate recesses to remove the n -AlAs/ i -GaAs/ n -AlGaAs virtual channel layers upon 2DEG channels are demonstrated. As compared to the D -mode device (sample A), the gate reverse currents are effectively reduced by 45 and 102 times for the E -mode devices with additional gate recess time of 24 s (sample B) and 30 s (sample C) to remove part of the virtual channel layers, respectively. Under gate forward bias, the hybrid gate recesses also enable the gate turn-on voltages to increase. Furthermore, the threshold voltages of –1.25, 0.09, and 0.22 V are observed in the samples A, B, and C, respectively. The maximum transconductances of 187.3, 209.2, and 243.4 mS/mm and saturation current density of 482.8, 410.6, and 347.4 mA/mm are obtained in the samples A, B, and C, respectively.

Inverter Logic of AlGaAs/InGaAs Enhancement/Depletion-Mode Pseudomorphic High Electron Mobility Transistors with Virtual Channel Layers

In this article, the direct-coupled FET logic (DCFL) inverters are implemented by co-integrated AlGaAs/InGaAs depletion-mode and enhancement-mode pseudomorphic high electron mobility transistors with virtual channel layers, and the inverters with varying gate width of the depletion-mode transistors are demonstrated. The experimental results show that the drain current IDS (mA/mm) and gm (mS/mm) per unit gate width increases as the gate widths of the depletion-mode devices decrease. This is attributed to the fact that the drain current and transconductance values are related to the channel-to-source resistance and the source contact resistance. When the gate width is reduced, the source pad contact area is only slightly changed and the IDS (mA/mm) as well as the transconductance gm (mS/mm) will increase. In addition, it is also observed that for the reduce of the gate width of the depletion-mode devices, the transfer characteristics of the DCFL inverters are steep and shift to the left due to the smaller drain saturation current of the load transistor.

Coevolution of Vaccination Opinions and Awareness Affecting the Spread of Epidemics

During the last decades, vaccines have been widely adopted to control or eliminate epidemics. Nevertheless, in practice, a vaccine is usually not completely effective, i.e., there may exist some side effects, which cause individuals to possess different opinions regarding vaccination. Thus, opinion transformation plays an important role in determining the range of epidemic infection. Individuals might be aware of risk due to the process of information spreading, which further affects the spread of epidemics. Moreover, awareness seems to affect the opinion transition process in turn. Motivated by these facts, we investigate the coevolution of vaccination opinion and awareness in a three-layered complex network. The opinion dynamics regarding vaccination evolves on the virtual layer, and the information also spreads on the same layer (for simplicity, these two processes are supported by the same topology). In contrast, biological elements carrying the viruses are transmitted through bodily contact on the physical layer. Furthermore, theoretical analyses through Markov chain are also provided for validation. The corresponding experimental analyses are then performed to investigate the effects of spread or loss of awareness on vaccination rate or epidemic size, and the results are presented and discussed.

Improving Spatial Locality in Virtual Machine for Flash Storage

Flash-based solid-state drives (SSD) are being widely adopted in virtualized environments to improve the I/O performance due to their low latency and high throughput compared with existing hard disk drives. In the virtualized environment, the performance of SSDs fluctuates significantly according to the I/O patterns from the virtual machine. For example, random writes have a significantly negative impact on the performance of SSDs compared with sequential writes due to the characteristics of SSDs. In this paper, we propose an address reshaping technique for SSDs in the virtualization layer to improve the spatial locality and the performance of random writes. Our scheme transforms random write requests into sequential write requests in the virtualization layer and thus enables the virtualization layer to issue the transformed sequential requests to SSDs. The experimental results show that the optimized scheme improves the performance by up to 97% compared with the existing scheme under random write workloads.

Cloud-Based FPGA Custom Computing Machines for Streaming Applications

A novel platform for launching and using field-programmable gate arrays (FPFA) custom computing machines (CCMs) in clouds and data centers is proposed. Based on a developed FPGA virtualization scheme, it allows users to create independent computing services on network-attached standalone FPGAs. The interface of the virtual FPGA (vFPGA)-based CCM is automatically generated by a virtualization layer and based on the user’s specifications. An FPGA hypervisor has been developed that can be easily integrated with any cloud management tool. It allows the users to launch/use/tear down vFPGA-based CCMs in a similar manner to conventional virtual machines (VMs). A complete prototype of the proposed platform has been realized and tested with a streamed image processing application. Its performance was 3–4 $\times$ and ~1.4–2.4 $\times$ times better than an SW implementation on a VM and a powerful server, respectively. Compared with other platforms for FPGA attachment to a cloud or datacenter, the proposed platform has relatively low overhead in terms of FPGA resources while providing the highest level of abstraction and virtualization.

Data Super-Network Fault Prediction Model and Maintenance Strategy for Mechanical Product Based on Digital Twin

When mechanical products work in complex environments, it is imperative to build an optimal maintenance strategy, based on accurate positioning of fault locations and prediction of fault conditions. Based on digital twinning technology, this paper proposes a “super-network-warning features” fault prediction and maintenance method. According to the digital twin five-dimensional structure, a three-layer super-network model is constructed, providing a quantitative research for data among heterogeneous subjects in digital twinning. Early-warning-features in the physical layer, virtual layer and service layer are selected as input parameters of the fault prediction model to accurately predict the cause of the fault. Then, using the simulation and optimization functions of the virtual model in digital twinning, a real-time maintenance strategy is formulated for the causes of the fault. It supplements the missing link between fault prediction and maintenance. Taking an aero-engine bearing as an example, this method is compared with a traditional method. The results show that the model prediction error of this method is better than the traditional method.

CER-CH: Combining Election and Routing Amongst Cluster Heads in Heterogeneous WSNs

Heterogeneous Wireless Sensor Networks (WSNs) are essential to the IoT vision. WSNs implement a virtual layer that can gather data about the real world. WSNs are composed of wireless battery powered devices that can have heterogeneous features related to computational power, memory, and communication capabilities. Because devices are battery powered, gathering data in an energy efficient way is crucial for the lifespan of the network. Clustering is a reasonable solution. This organises the devices into sets (clusters). Each cluster has a cluster head (CH) that gathers data from the nodes belonging to its cluster and communicates with other CHs in order to report data to a centralised base station (BS). This is usually achieved via a CH routing tree that is rooted at the BS. Beside clustering, the rotation in the role of CHs amongst the nodes of the network is a standard means to better distribute energy consumption. In this paper we propose a novel approach (CER-CH) where the CH routing tree definition and the CH rotation are combined together. More precisely, starting from any clustering criteria, we propose a novel rotation heuristic combined with a novel top-down CH routing tree definition in order to balance the node energy consumption and generate more energy efficient CH routing trees. Our experiments show that our rotation strategy enhances on average the network lifespan of 20% when compared to the state of art protocols.

Combining containers and virtual machines to enhance isolation and extend functionality on cloud computing

Virtualization technology is the underlying element of cloud computing. Traditionally, cloud computing has employed virtual machines to distribute available resources and provide isolated environments among users. Multiple virtual machines, with their own operating system and services, can be deployed and run simultaneously on the same physical machine on the cloud infrastructure. Recently, a more lightweight virtualization technology is being rapidly adopted and it is based on containers. A key difference between virtual machines and containers, is that containers share the same underlying operating system.In this work, we studied the combination of these two virtualization technologies by running containers on top of virtual machines. This synergy aims to enhance containers’ main drawback, which is isolation and, among others, to simplify the system management and upgrade, and to introduce the new functionalities of containerized applications to virtual machines. The benefits of this method have been recognized by big cloud companies, which have been employing this approach for years.With this paper, we aimed to present the advantages of running containers on virtual machines and to explore how various virtualization techniques and configurations affect the performance of this method. Although, in bibliography there are a few papers that used this method partially to conduct experiments, there is not any research which considers this method from our integral aspect of view. In this study, we ran Docker containers and evaluated their performances, not only on KVM and XEN virtual machines, but also we ran Linux containers on Windows Server. We adopted an empirical approach, to quantify the performance overhead introduced by the additional virtualization layer of virtual machines, by executing various benchmarks and deploying real world applications as use cases. Furthermore, we presented for first time, how isolation is applied on virtual machines and containers, we evaluated different operating systems optimized to host containers, mechanisms of storing persistent data and, last but not least, we experimentally quantified the power and energy consumption overhead of containers running on virtual machines.