Wide Area Network Environment Research Articles

Data Utilization-Based Adaptive Data Management Method for Distributed Storage System in WAN Environment

Recently, research on a distributed storage system that efficiently manages a large amount of data has been actively conducted following data production and demand increase. Physical expansion limits exist for traditional standalone storage systems, such as I/O and file system capacity. However, the existing distributed storage system does not consider where data is consumed and is more focused on data dissemination and optimizing the lookup cost of data location. And this leads to system performance degradation due to low locality occurring in a Wide Area Network (WAN) environment with high network latency. This problem hinders deploying distributed storage systems to multiple data centers over WAN. It lowers the scalability of distributed storage systems to accommodate data storage needs. This paper proposes a method for distributing data in a WAN environment considering network latency and data locality to solve this problem and increase overall system performance. The proposed distributed storage method monitors data utilization and locality to classify data temperature as hot, warm, and cold. With assigned data temperature, the proposed algorithm adaptively selects the appropriate data center and places data accordingly to overcome the excess latency from the WAN environment, leading to overall system performance degradation. This paper also conducts simulations to evaluate the proposed and existing distributed storage methods. The result shows that our proposed method reduced latency by 38% compared to the existing method. Therefore, the proposed method in this paper can be used in large-scale distributed storage systems over a WAN environment to improve latency and performance compared to existing methods, such as consistent hashing.

A Scalable Byzantine Fault Tolerance Algorithm Based on a Tree Topology Network

The consortium chain is the main form of application of blockchain technology in the actual industry, and its consensus mechanism mostly adopts the practical Byzantine fault tolerance (PBFT) algorithm. The traditional PBFT algorithm is only suitable for small-scale local area networks, but in large-scale wide-area network environments, its scalability bottleneck has a serious impact on the performance of the system. Therefore, in this paper, a scalable Byzantine fault tolerance algorithm based on a tree topology network is proposed (STBFT), which can take different steps to reach consensus according to the abnormal situation of the system. First, the STBFT algorithm divides the consensus nodes into different layers and groups based on the tree topology network structure, which transforms from global consensus to local consensus and drastically reduces communication consumption. Then, the division method of the group is based on a verifiable random function (VRF), with the purpose of preventing targeted attacks and colluding Byzantine nodes from affecting the normal consensus of the system. Finally, a feedback mechanism is proposed for the first time to reduce the influence of Byzantine failure on hierarchical network systems. The simulation results show that the proposed algorithm reduces the communication complexity and improves the fault tolerance of the system, and the scalability of the tree topology network structure can be better applied in large-scale scenarios such as IoT and health care.

Mobile GPU-based implementation of automatic analysis method for long-term ECG

BackgroundLong-term electrocardiogram (ECG) is one of the important diagnostic assistant approaches in capturing intermittent cardiac arrhythmias. Combination of miniaturized wearable holters and healthcare platforms enable people to have their cardiac condition monitored at home. The high computational burden created by concurrent processing of numerous holter data poses a serious challenge to the healthcare platform. An alternative solution is to shift the analysis tasks from healthcare platforms to the mobile computing devices. However, long-term ECG data processing is quite time consuming due to the limited computation power of the mobile central unit processor (CPU).MethodsThis paper aimed to propose a novel parallel automatic ECG analysis algorithm which exploited the mobile graphics processing unit (GPU) to reduce the response time for processing long-term ECG data. By studying the architecture of the sequential automatic ECG analysis algorithm, we parallelized the time-consuming parts and reorganized the entire pipeline in the parallel algorithm to fully utilize the heterogeneous computing resources of CPU and GPU.ResultsThe experimental results showed that the average executing time of the proposed algorithm on a clinical long-term ECG dataset (duration 23.0 ± 1.0 h per signal) is 1.215 ± 0.140 s, which achieved an average speedup of 5.81 ± 0.39× without compromising analysis accuracy, comparing with the sequential algorithm. Meanwhile, the battery energy consumption of the automatic ECG analysis algorithm was reduced by 64.16%. Excluding energy consumption from data loading, 79.44% of the energy consumption could be saved, which alleviated the problem of limited battery working hours for mobile devices.ConclusionThe reduction of response time and battery energy consumption in ECG analysis not only bring better quality of experience to holter users, but also make it possible to use mobile devices as ECG terminals for healthcare professions such as physicians and health advisers, enabling them to inspect patient ECG recordings onsite efficiently without the need of a high-quality wide-area network environment.

Performance measurement using dpdk in software-defined local and wide area networks

Background/Objectives: For data center-based enterprises, the use of data traffic continues to increase. As a result, the increasingly efficient processing of increasing data traffic is becoming a major issue. Effective processing of traffic can be performed through the addition of physical network equipment, but this requires considerable costs.Methods/Statistical analysis: To solve this problem, researches on server virtualization and network virtualization technology are being actively conducted. However, while network virtualization is a cost-effective solution, open-source virtual switches used in network virtualization technologies have the performance penalty because they handle packets at the kernel of server's operating system. As a result, the Intel has developed the Data Plane Development Kit (DPDK) technology to address the performance degradation of the operating system.Findings: In this paper, we propose the DPDK performance test environment based on Open Virtual Switch (OVS) to verify the stability and performance of the DPDK-oriented virtualization technology, in association with a new KREONET-S project which aims tothe softwarization of the Korea Research Environment Open Network (KREONET) infrastructure.Improvements/Applications: We perform conducted experiments on Software-Defined Local Area Network (LAN) and Wide Area Network (WAN) environment using KREONET-S show the result.

A Metadata Redundancy Approach for File Systems over Lossy Packet-based Network

Wide Area Network (WAN) has the characteristics of high latency and packet loss. Traditionally, WAN-based file systems use TCP to transfer data and metadata. Due to the properties of TCP, if packet loss occurs during transmission, the sender has to resend the lost contents after timeout, which incurs delay, resulting low performance. In this paper, we propose a metadata redundancy approach to address the issue. We use replication as well as erasure coding to produce redundant data at the server side and send it with the original data using UDP, if the client detects metadata loss and the loss is recoverable, it can recover the metadata locally at client side, which greatly improves file system performance. We carry out performance tests in a simulated WAN environment to evaluate our method. Compared with TCP, test results show our approach achieve good performance in severe delay and persistent packet loss environment.

Memory Virtualization Technique for Efficient Access of Data Resources in Cloud Environment

Working in cloud environment and accessing its services is fascinating task. It is one of modern technological areas to work upon it for development of nation and increase economy rate. The paper deals with improving desktop cloud computing services with the help of technique called Memory Virtualization. Since virtualization is efficient to extent scalability of typical desktop-as-a-service and make it suitable for Wide Area Network (WAN’s) environments. Desktop-as-a-Service (DaaS) in cloud computing means that user can access its own desktop services as well as services of other desktops located on remote servers. Memory virtualization not only works with virtual memory but it also maps physical memory instructions to actual machine memory. The instructions stored in machine memory are checked with incoming user client requests. Similar matched queries will result in generation of data using one of recovery techniques called Shadow Paging Technique. Data is produced and stored in remote cloud environment where user can access the data to perform their tasks. The proposed systematic model for accessing desktop services is shown in following paper by using memory virtualization technique. A comparison is also made between paravirtualization technique and memory virtualization technique that gives solution in favor of memory virtualization technique.

Distributed Storage and Processing Method for Big Data Sensing Information of Machine Operation Condition

The traditional relational database cannot satisfy the requirements of the high speed and real-time storage and processing for the distributed Big Data sensing information in the Wide Area Network environment. In this context, the No-SQL database HBase is used to store the big data sensing information of machine operation condition collected by Fiber Bragg Grating sensor network. The distributed storage environment and the optimal database table scheme is built. Moreover, the HBase Rowkey is designed in detail to sharpen the retrieval speed and avoid the server hot point accumulation. Meanwhile, the real-time outlier detection method with the working situational constraint is proposed to monitor the machine working condition. It is implemented by the multi-dimensional histogram statistics method in the Map Reduce distributed environment. Hence, the traditional threshold monitoring method is improved and the false alarm problem is eliminated. Through balancing the performance between HBase and the relational database MySQL, the real-time storage rate of the proposed method can satisfy at least 20 machines running concurrency with 4000 Hz Fiber Bragg Grating sampling frequency by HBase. Also, the effectiveness of real-time outlier detection method is proved by the practical operation data processing.

Performance of the Precision Time Protocol for clock synchronisation in smart grid applications

ABSTRACTAccurate time stamping is essential for reliable operation of the automation and control systems used across a smart grid. This paper investigates the performance of the Precision Time Protocol (PTP) for time distribution over the telecommunication networks interconnecting such systems. Distributed clocks are arranged in a PTP master‐slave hierarchy and can be synchronised to an international time standard with sub‐microsecond accuracy. Using Hydro Québec's telecommunications facilities, we investigate the synchronisation error that is observed using some of the latest PTP clock prototypes over a widely spread network. As such, field trials are performed by deploying PTP master and slave clocks in distant sites of Hydro Québec's wide area network (WAN). A thorough analysis of these trial outcomes is further conducted using laboratory experiments that point out the impact of different parameters such as the PTP messages rate, as well as the link bandwidth and asymmetry. Our analysis leads to important criteria for optimal PTP system design in a WAN environment using appropriate clock and network parameter settings. Improving the PTP clocks internal features is also part of this optimal design, since it is necessary for maintaining the required synchronisation performance in power grid applications running under scarce communication network bandwidth conditions. Copyright © 2013 John Wiley & Sons, Ltd.

SuperB R&D computing program: HTTP direct access to distributed resources

The SuperB asymmetric energy e+e− collider and detector to be built at the newly founded Nicola Cabibbo Lab will provide a uniquely sensitive probe of New Physics in the flavor sector of the Standard Model. Studying minute effects in the heavy quark and heavy lepton sectors requires a data sample of 75 ab−1 and a luminosity target of 1036cm−2s−1. The increasing network performance also in the Wide Area Network environment and the capability to read data remotely with good efficiency are providing new possibilities and opening new scenarios in the data access field. Subjects like data access and data availability in a distributed environment are key points in the definition of the computing model for an HEP experiment like SuperB. R&D efforts in such a field have been brought on during the last year in order to release the Computing Technical Design Report within 2013. WAN direct access to data has been identified as one of the more interesting viable option; robust and reliable protocols as HTTP/WebDAV and xrootd are the subjects of a specific R&D line in a mid-term scenario. In this work we present the R&D results obtained in the study of new data access technologies for typical HEP use cases, focusing on specific protocols such as HTTP and WebDAV in Wide Area Network scenarios. Reports on efficiency, performance and reliability tests performed in a data analysis context have been described. Future R&D plan includes HTTP and xrootd protocols comparison tests, in terms of performance, efficiency, security and features available.

Applying Wireless Classroom to Build a Highly Interactive Learning Environment

Wireless networks now support Web browsing, email, real-time chat, and access to remote computing resources. With the increasing use of small portable computers, this emerging communications infrastructure will enable many new Internet applications. The innovative project at the Yangtze University is currently exploring how educators can use portable handheld computers with wireless Internet access to improve teaching and learning in both local and wide area network environments.

Optimization Technique for Virtual Topology Reconfiguration for IP-over-WDM Networks with QoS Parameters

This paper, researches about the application of optimization techniques for the reconfiguration of optical internets using IP-over-WDM technology. Internet Protocol (IP) over Wavelength Division Multiplexed (WDM) networking technology with Terabits per second bandwidth become a natural choice for the future generation internet networks (Optical Internets), wide area network (WAN) environments and backbone networks due to its potential ability to meet rising demands of high bandwidth and low latency communication. Recently Virtual Topology Reconfiguration of IP over WDM networks has received greater attention among researchers. Optimation technique finds many applications in the field of network engineering, which includes linear programming, traffic prediction, network modeling, traffic modeling, etc. In this paper, we have presented a new approach for reconfiguring virtual topology of IP over WDM networks using optimization technique. The computed results show that this new approach achieves better performance in terms of computational accuracy, number of changes and average weighted hop count.

Live Virtual Machine Migration via Asynchronous Replication and State Synchronization

Live migration of virtual machines (VM) across physical hosts provides a significant new benefit for administrators of data centers and clusters. Previous memory-to-memory approaches demonstrate the effectiveness of live VM migration in local area networks (LAN), but they would cause a long period of downtime in a wide area network (WAN) environment. This paper describes the design and implementation of a novel approach, namely, CR/TR-Motion, which adopts checkpointing/recovery and trace/replay technologies to provide fast, transparent VM migration for both LAN and WAN environments. With execution trace logged on the source host, a synchronization algorithm is performed to orchestrate the running source and target VMs until they reach a consistent state. CR/TR-Motion can greatly reduce the migration downtime and network bandwidth consumption. Experimental results show that the approach can drastically reduce migration overheads compared with memory-to-memory approach in a LAN: up to 72.4 percent on application observed downtime, up to 31.5 percent on total migration time, and up to 95.9 percent on the data to synchronize the VM state. The application performance overhead due to migration is kept within 8.54 percent on average. The results also show that for a variety of workloads migrated across WANs, the migration downtime is less than 300 milliseconds.

WebGIS Intelligent Diagnosis and Forecasting System of Plant Diseases

With the computer and the rapid development of information technology, The plant disease intelligence diagnosis and the plant disease early warning network is possible. In this paper, relying on the Internet, the realization of intelligent online plant disease diagnosis, early warning, prevention and other information query and forecasting capabilities. The database base on Internet-based wide area network environment and the help of webGIS technology, including diagnostic module, check module and the prediction module. The intelligent prognosis is tested to the extent and happening of plant diseases, for example, Wheat, cotton, tomatoes and other 12 kinds of plant diseases, and epidemic curve is given. To disease diagnosis and prediction of the professional, technical problems become easy, for the effective control of plant diseases, provide a reference.

Mechanism of a Resource Location Approach in Power-Law Networks

How to effectively locate resources is a very important factor affecting the performance of distributed system in wide area network environments. Some resource location methods have been already proposed, which utilize Small World phenomena, but have not show how to construct a Small World exactly. In this paper, on the base of Kleinberg Small World model, aimed power-law characteristics, an efficient decentralized construction approach PLSWCP(Power-law oriented Small World Construction Protocol) is proposed, which uses fairly small partial view instead of global knowledge of network. Theoretical analysis and simulations show that PLSWCP is scalable, self-adaptable, and load-balanced, improving the efficiency of resource location.

Eight Times Acceleration of Geospatial Data Archiving and Distribution on the Grids

A grid-powered Web Geographical Information Science (GIS)/Web Processing Service (WPS) system has been developed for archiving and distributing large volumes of geospatial data. However, users, WPS servers, and data resources are always distributed across different locations, attempting to access and archive geospatial data from a GIS survey via conventional Hypertext Transport Protocol, Network File System Protocol, and File Transfer Protocol, which often encounters long waits and frustration in wide area network (WAN) environments. To provide a ldquolocal-likerdquo performance, a WAN/grid-optimized protocol known as ldquoGridJetrdquo developed at our lab was used as the underlying engine between WPS servers and clients, which utilizes a wide range of technologies including the one of paralleling the remote file access. No change in the way of using software is required since the multistreamed GridJet protocol remains fully compatible with the existing IP infrastructures. Our recent progress includes a real-world test that PyWPS and Google Earth over the GridJet protocol beat those over the classic ones by a factor of two to eight, where the distribution/archiving distance is over 10 000 km.

Performance analysis of mobile agents

The results of a performance analysis of mobile agents in a distributed network environment are presented. Analytical models are developed and used to compare the performance of carrying out a simple management function with mobile agents (MA) or SNMP (simple network management protocol). An examination is made of how delay is affected by the size of the management domain and how each method behaves in both a local area network (LAN) and wide area network (WAN) environment. For large domains, optimal performance is obtained if the mobile agents' size is bounded, and this may require sharing the management task among a small number of mobile agents.

Simulation of optical network operation using simulator ns-2

Optical wavelength division multiplexing (WDM3) networking technology has been identified as a suitable candidate for future wide area network (WAN4) environments, due to its potential ability to meet rising demands of high bandwidth and low latency communication. Networking protocols and algorithms are being developed to meet the changing operational requirements in future optical WANs (OWAN).

TCP-LP: low-priority service via end-point congestion control

Service prioritization among different traffic classes is an important goal for the Internet. Conventional approaches to solving this problem consider the existing best-effort class as the low-priority class, and attempt to develop mechanisms that provide "better-than-best-effort" service. In this paper, we explore the opposite approach, and devise a new distributed algorithm to realize a low-priority service (as compared to the existing best effort) from the network endpoints. To this end, we develop TCP Low Priority (TCP-LP), a distributed algorithm whose goal is to utilize only the excess network bandwidth as compared to the "fair share" of bandwidth as targeted by TCP. The key mechanisms unique to TCP-LP congestion control are the use of one-way packet delays for early congestion indications and a TCP-transparent congestion avoidance policy. The results of our simulation and Internet experiments show that: 1) TCP-LP is largely non-intrusive to TCP traffic; 2) both single and aggregate TCP-LP flows are able to successfully utilize excess network bandwidth; moreover, multiple TCP-LP flows share excess bandwidth fairly; 3) substantial amounts of excess bandwidth are available to the low-priority class, even in the presence of "greedy" TCP flows; 4) the response times of web connections in the best-effort class decrease by up to 90% when long-lived bulk data transfers use TCP-LP rather than TCP; 5) despite their low-priority nature, TCP-LP flows are able to utilize significant amounts of available bandwidth in a wide-area network environment

On the performance of wide-area thin-client computing

While many application service providers have proposed using thin-client computing to deliver computational services over the Internet, little work has been done to evaluate the effectiveness of thin-client computing in a wide-area network. To assess the potential of thin-client computing in the context of future commodity high-bandwidth Internet access, we have used a novel, noninvasive slow-motion benchmarking technique to evaluate the performance of several popular thin-client computing platforms in delivering computational services cross-country over Internet2. Our results show that using thin-client computing in a wide-area network environment can deliver acceptable performance over Internet2, even when client and server are located thousands of miles apart on opposite ends of the country. However, performance varies widely among thin-client platforms and not all platforms are suitable for this environment. While many thin-client systems are touted as being bandwidth efficient, we show that network latency is often the key factor in limiting wide-area thin-client performance. Furthermore, we show that the same techniques used to improve bandwidth efficiency often result in worse overall performance in wide-area networks. We characterize and analyze the different design choices in the various thin-client platforms and explain which of these choices should be selected for supporting wide-area computing services.

Impact of Admission and Cache Replacement Policies on Response Times of Jobs on Data Grids

Caching techniques have been used widely to improve the performance gaps of storage hierarchies in computing systems. Little is known about the impact of policies on the response times of jobs that access and process very large files in data grids, particularly when data and computations on the data have to be co-located on the same host. In data intensive applications that access large data files over wide area network environment, such as data-grids, the combination of policies for job servicing (or scheduling), caching and cache replacement can significantly impact the performance of grid jobs. We present preliminary results of a simulation study that combines an admission policy with a cache replacement policy when servicing jobs submitted to a storage resource manager.The results show that, in comparison to a first come first serve policy, the response times of jobs are significantly improved, for practical limits of disk cache sizes, when the jobs that are back-logged to access the same files are taken into consideration in scheduling the next file to be retrieved into the disk cache. Not only are the response times of jobs improved, but also the metric measures for caching policies, such as the hit ratio and the average cost per retrieval, are improved irrespective of the cache replacement policy used.