Wide Area Network

Trimble Terrasat as software and development engineer where he is working on high precision kinematic positioning using the future Galileo system. Dr. Ulrich Vollath received a Ph.D. in Computer Science from the Munich University of Technology (TUM) in 1993. At Trimble Terrasat -where he is working on GPS algorithms since more than eleven years -he is responsible for the Algorithm Development team. His professional interest is focused on high-precision real-time kinematic positioning and reference station network processing. Francisco Amarillo is the ESA/ESTEC technical officer responsible for the investigation on four carrier ambiguity resolution.

LoRaWAN (Long Range Wide Area Network) contributes as a key technology in Industrial Internet of Things (IIoT). LoRaWAN receives consistent industrial attention due to its far-reaching long-range communication capability, low power consumption, and easy-to-adapt architecture, which requires minimal infrastructure costs. This paper provides more insightful information about LoRaWAN in IIoT, illustrating how LoRaWAN optimises operational efficiency, safety, remote data collection, and sustainability through its dynamic features in industrial settings. Additionally, this paper explores the integration of LoRaWAN with emerging technologies, including artificial intelligence, machine learning, edge computing, and blockchain. While this paper emphasizes the potential of promising trends in the IIoT ecosystem, it also explores relevant challenges like scalability, security, and interoperability that demand the need for continued research. The comparative analysis of recent research works highlights key technical parameters. It is helpful to critically examine the trade-offs between performance, scalability, and security, and address them with novel solutions. In summary, this paper offers valuable insights for industry professionals and researchers seeking to leverage LoRaWAN to advance the Industrial Internet of Things (IIoT).

This paper presents Hamster, a novel synchronous Byzantine Fault Tolerant protocol that achieves high throughput and weaker dependency on synchrony. Specifically, Hamster is the first to introduce coding techniques into synchronous BFT, addressing the challenges posed by higher fault tolerance requirements and significantly reducing communication complexity. Consequently, Hamster achieves linear throughput gains as the number of nodes increases, surpassing Sync HotStuff. Additionally, with minor modifications, Hamster can operate effectively in mobile sluggish environments, further reducing its dependency on strict synchrony. We implement Hamster, and experimental results highlight its performance advantages. Specifically, Hamster achieves 2.5× the throughput of Sync HotStuff in a network of 9 nodes, with this gain growing to 10× as the network scales to 65 nodes. This increasing throughput advantage makes Hamster more applicable to largescale distributed systems.

The large base of Internet-enabled smartphones provides an excellent opportunity for a fine-grained observation of the structure of the Internet and a quantitative evaluation of its characteristics. Smartphones can operate as active mobile monitors and, coordinated by a central entity, they can probe the network on a local scale. Then the results produced by a large number of participants can be merged to obtain a detailed graph of the Internet. Besides the design of the measurement framework, this paper describes the implementation and validation of a traceroute-like tool that is compatible with the Android platform. This confirms that smartphone-based crowdsourcing of network properties can be a viable strategy.

Globally, hydro-power has been considered the cheapest renewable source of energy. This form of energy production entirely depends on the water levels which in turn causes a major concern of ensuring that the monitoring systems involved are capable of ensuring monitoring in the prevention of disasters. The disasters involved range from floods and drought conditions that would lead to low power production led by lack of enough water draining in the reservoirs'. Several systems have been implemented towards coming up with a convenient and efficient monitoring system. With the freedom given to software developers in developing the systems, evaluation of the performance of the system must be performed to enable this transformation. Therefore, the study selected n already existing real-time monitoring system using Lora Technology in hydroelectric monitoring to conduct the performance validation. A total of one hundred and twenty readings were taken to be validated with the other models used. Consistency, accuracy, latency, and throughput were the metrics used to validate the IoT-based model's performance. During the performance validation, the study found that the system achieved all the functionalities expected in its assessment. Therefore, IoT-based systems have the potential to inform future hydroelectric monitoring practices

Globally, hydro-power has been considered the cheapest renewable source of energy. This form of energy production entirely depends on the water levels which in turn causes a major concern of ensuring that the monitoring systems involved are capable of ensuring monitoring in the prevention of disasters. The disasters involved range from floods and drought conditions that would lead to low power production led by lack of enough water draining in the reservoirs'. Several systems have been implemented towards coming up with a convenient and efficient monitoring system. With the freedom given to software developers in developing the systems, evaluation of the performance of the system must be performed to enable this transformation. Therefore, the study selected n already existing real-time monitoring system using Lora Technology in hydroelectric monitoring to conduct the performance validation. A total of one hundred and twenty readings were taken to be validated with the other models used. Consistency, accuracy, latency, and throughput were the metrics used to validate the IoT-based model's performance. During the performance validation, the study found that the system achieved all the functionalities expected in its assessment. Therefore, IoT-based systems have the potential to inform future hydroelectric monitoring practices

In recent years, the migration of the computational workload to computational clouds has attracted intruders to target and exploit cloud networks internally and externally. The investigation of such hazardous network attacks in the cloud network requires comprehensive network forensics methods (NFM) to identify the source of the attack. However, cloud computing lacks NFM to identify the network attacks that affect various cloud resources by disseminating through cloud networks. In this paper, the study is motivated by the need to find the applicability of current (C-NFMs) for cloud networks of the cloud computing. The applicability is evaluated based on strengths, weaknesses, opportunities, and threats (SWOT) to outlook the cloud network. To the best of our knowledge, no research to date has been conducted to assist network forensics investigators and cloud service providers in finding an optimal method for investigation of network vulnerabilities found in cloud networks. To this end and in this paper, the state-of-the-art C-NFMs are classified and analyzed based on the cloud network perspective using SWOT analysis. It implies that C-NFMs have a suitable impact on cloud network, which further requires for reformation to ensure its applicability in cloud networks.

Software integration is a crucial aspect of collaborative software applications and systems. It enables a number of different software applications, created by different developers, using different programming languages, and even located at different places to work with each other collaboratively to achieve common goals. Nowadays, a number of techniques are available to enable software integration. Messaging is the most prominent technique in this respect. In this paper, two leading open-source messaging brokers, Apache ActiveMQ and Apache Apollo, have been experimentally compared with each other with regard to their messaging capabilities (message sending and receiving throughputs). Both brokers support exchanging messages between heterogeneous and distributed software applications using several messaging mechanisms including Java Message Service (henceforth JMS). A number of experimental test scenarios have been conducted to obtain the comparison results that indicate the one-to-o...

I, Amanullah Maung Than Oo, declare that the PhD thesis entitled -Experimental Analysis and Modelling of an Information Embedded Power System‖ is no more than 100,000 words in length, exclusive of tables, figures, appendices and references. This thesis contains no material that has been submitted previously, in whole or in part, for the award of any other academic degree or diploma. Except where otherwise indicated, this thesis is my own work.

AMOEBA is a research project to build a true distributed operating system using the object model. Under the COST11-ter MANDIS project this work was extended to cover wide-area networks. Besides describing the system, this paper discusses the successive versions in the implementation of its model, and why the changes were made. Its purpose is to prevent ourselves and others from making the same mistakes again, and to illustrate how a distributed operating system grows in sophistication and size. "Those who learn nothing fi'om history are doomed to repeat it" --Santayana For about eight years now, we have been doing research on distributed operating systems, not only behind our desks, but also behind our terminals. The distributed system we are developing is called AMOEBA[l], and it is constantly evolving. It is being developed at the Vrije Universiteit and the Centre for Mathematics and Computer Science (CWI), both in Amsterdam. AMOEBA currently runs on Motorola 68020, National Semiconductor 32032, and MicroVax II processors. Both Ethemet and the Pronet token ring are supported by AMOEBA, and can be connected by a bridge. COST11-ter MANDIS is an international project investigating the management requirements for large international networks of computers. It has adopted the object-model as a framework within which to discuss the management of wide-area distributed systems. To experiment with this, the MANDIS project adopted the Amoeba distributed operating system, extended with a gateway for wide-area communication. Amoeba systems in Holland (Vrije Universiteit, CWI), the U.K. (Harwell Laboratories, Haffield Polytechnic), in Berlin (GMD/FOKUS) and in Norway (University of Troms0) have been connected into a single, transparent distributed system.

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To alleviate scalability problems in the Web, many researchers concentrate on how to incorporate advanced caching and replication techniques. Many solutions incorporate object-based techniques. In particular, Web resources are considered as distributed objects offering a well-defined interface. We argue that most proposals ignore two important aspects. First, there is little discussion on what kind of coherence should be provided. Proposing specific caching or replication solutions makes sense only if we know what coherence model they should implement. Second, most proposals treat all Web resources alike. Such a one-size-fits-all approach will never work in a wide-area system. We propose a solution in which Web resources are encapsulated in physically distributed shared objects. Each object should encapsulate not only state and operations, but also the policy by which its state is distributed, cached, replicated, migrated, etc.

Achieving high performance for distributed I/O on a wide‐area network continues to be an elusive holy grail. Despite enhancements in network hardware as well as software stacks, achieving high‐performance remains a challenge. In this paper, our worldwide team took a completely new and non‐traditional approach to distributed I/O, called ParaMEDIC: Parallel Metadata Environment for Distributed I/O and Computing, by utilizing application‐specific transformation of data to orders of magnitude smaller metadata before performing the actual I/O. Specifically, this paper details our experiences in deploying a large‐scale system to facilitate the discovery of missing genes and constructing a genome similarity tree by encapsulating the mpiBLAST sequence‐search algorithm into ParaMEDIC. The overall project involved nine computational sites spread across the U.S. and generated more than a petabyte of data that was ‘teleported’ to a large‐scale facility in Tokyo for storage. Copyright © 2010 Joh...

Achieving high performance for distributed I/O on a wide-area network continues to be an elusive holy grail. Despite enhancements in network hardware as well as software stacks, achieving high-performance remains a challenge. In this paper, our worldwide team took a completely new and non-traditional approach to distributed I/O, called ParaMEDIC: Parallel Metadata Environment for Distributed I/O and Computing, by utilizing application-specific transformation of data to orders-of-magnitude smaller meta-data before ...

We consider the estimation of the arrival rate and the service time moments of a M/G/1 queue with probing, i.e., with special customers (probes) entering the system. The probe inter-arrival times are i.i.d. and probe service times follow a general positive distribution. The only observations used are the arrival times, service times and departure times of probes. We derive the main equations from which the quantities of interest can be estimated. Two particular probe arrivals, deterministic and Poisson, are investigated.

I, Amanullah Maung Than Oo, declare that the PhD thesis entitled -Experimental Analysis and Modelling of an Information Embedded Power System‖ is no more than 100,000 words in length, exclusive of tables, figures, appendices and references. This thesis contains no material that has been submitted previously, in whole or in part, for the award of any other academic degree or diploma. Except where otherwise indicated, this thesis is my own work.

The TeraPaths project at Brookhaven National Laboratory is pioneering a framework that enables the scheduling of network resources in the context of data-intensive scientific computing. Modern wide area networks, such as ESnet and Internet2, have recently started providing network resource reservation capabilities in the form of virtual circuits. The TeraPaths framework utilizes these circuits and extends them into end-site local area networks, establishing end-to-end virtual paths between end-site hosts. These paths are dedicated to specific users and/or applications and provide guaranteed resources, minimizing or eliminating the adverse effects of network congestion. In this article, we present an overview of TeraPaths and examine issues raised by the end-to-end resource reservation-based networking paradigm as well as implications and benefits for end users and applications. We also discuss scalability issues and optimization techniques for wide area network circuit reservations.

1. Information provided by tracking studies using satellite telemetry is providing ecologists with invaluable new insights into animal behaviour and movement strategies. Here we describe a new type of GPS (global positioning system) tracking device which makes use of a growing network of LoRaWAN (long range, low power wide area network) gateways. These tags have the potential to be a low weight and power consumption solution. 2. We characterise the GPS accuracy and data transmission range, including uplinks and downlinks, for the tracker using a series of standardised tests. Data transmission range was tested by visiting locations with line of sight to the LoRa gateway at distances up to 75km and recording whether data transmission was completed successfully from each location. These tests were complemented by a trial deployment of six devices on Griffon Vultures Gyps fulvus. 3. These LoRa tags reliably provided accurate GPS location estimates, particularly on shorter location acqui...

Malaysian National Center for Education estimates that students' enrolments will increase to 17.2 million by 2028. The conventional way of managing things around campus work can be  improved by applying the smart campus concept. This study showcases the potential smart campus applications with different wireless IoT technologies and their application; LoRa for Internet of Bicycle (IoB), Sigfox for water quality monitoring, IEEE 801.11p for campus active safety application, and NB-IoT for remote mangrove conservation. The prototypes consist of various sensors and online dashboards to demonstrate the open-source IoT ecosystem. For IoB, a 0.5 km radius centered at LoRa gateway’s location, proved reliable for real-time e-bicycles location monitoring. It offers locking system security to avoid bicycles steal. The SigFox-based water quality monitoring system received signal performance is adequate (RSSI -80 to -90 dBm) with a  tower location approximately 3 km from the lake area. For ...

Novel bitwise retransmission schemes are devised which retransmit only the bits received with small reliability. The retransmissions are used to accumulate the reliabilities of individual bits. Unlike the conventional automatic repeat request (ARQ) schemes, the proposed scheme does not require a checksum for the error detection. The bits to be retransmitted are reported as a combination number, or two synchronized random number generators (RNGs) at the transmitter and receiver are used to greatly compress the feedback message. The bitwise retransmission decisions and/or combining can be performed after the demodulation or after the channel decoding at the receiver. The bit-error rate (BER) expressions are derived for the case of one and two retransmissions, and verified by computer simulations. Assuming three specific retransmission strategies, the scheme parameters are optimized to minimize the overall BER. For the same number of retransmissions and packet length, the proposed schemes always outperform the frequently used stop-and-wait ARQ. The impact of feedback errors is also considered. Finally, practical designs of the bitwise retransmissions for data fusion from sensor nodes in Zigbee, Wifi and Bluetooth networks are presented.

Novel bitwise retransmission schemes are devised which retransmit only the bits received with small reliability. The retransmissions are used to accumulate the reliabilities of individual bits. Unlike the conventional automatic repeat request (ARQ) schemes, the proposed scheme does not require a checksum for the error detection. The bits to be retransmitted are reported as a combination number, or two synchronized random number generators (RNGs) at the transmitter and receiver are used to greatly compress the feedback message. The bitwise retransmission decisions and/or combining can be performed after the demodulation or after the channel decoding at the receiver. The bit-error rate (BER) expressions are derived for the case of one and two retransmissions, and verified by computer simulations. Assuming three specific retransmission strategies, the scheme parameters are optimized to minimize the overall BER. For the same number of retransmissions and packet length, the proposed sche...

The large capacity of optical fibers suggests that circuit-switching may become a more attractive switching method in future communication networks. We show, however, that under some reasonable assumptions the delays associated with circuit-switching make the technique inferior to packet-switching in a high-performance, distributed environment. A network design that demonstrates the feasibility of packet-switching in high-performance environment is also presented. This work was sponsored in part by the Defense Advanced Research Projects Agency under contract N00039-86-K-0431, by the Digital Equipment Corporation, by ATT Information Systems and by Bell Northern Research.

This paper presents an analytical framework for
evaluating auxiliary cache utility data structures in vector
databases and local large language model (LLM) retrieval
pipelines. While frequency-based caching policies such as
TinyLFU are well-established in mature systems, the incremental
value of a dedicated auxiliary cache layer that sits between
application logic and existing caching mechanisms remains an
open question. We develop a formal mathematical model for
analyzing cache utility and present a structured assessment
methodology examining architectural trade-offs. Our analysis
encompasses system complexity, maintenance burden, and cache
coherence challenges against potential performance benefits. We
systematically compare architectural approaches across different
deployment scenarios and query workloads, identifying conditions
where auxiliary caches might provide meaningful benefits beyond
existing mechanisms. Rather than making empirical claims
that would require extensive benchmarking, we contribute a
decision framework that system architects can apply to their
specific contexts. We conclude by identifying key experimental
metrics and validation approaches that would be necessary
to quantitatively evaluate auxiliary cache implementations in
production environments.

The scope of Internet of Things (IoT) technologies is expanding year by year. One such area is the engineering of systems for collecting and transmitting information from various sensors for further processing and possible control of technological systems. Examples of such systems are "smart city" systems, environmental pollution control systems, natural disasters forecasting systems, soil moisture systems, etc. The technologies and protocols for building such systems must, first and foremost, be characterized by low energy consumption and cover large territorial areas. The technology of this class is commonly known as LPWAN (Low-power Wide-area Network). This paper solves the problem of analyzing the features of LPWAN technologies by the criteria: openness, coverage range, data rate and deployment cost, for further use in the construction of engineering systems for collecting and transmitting information from various sensors for further processing and possible control of ...

With the rapid evolution of network technologies, ensuring secure and efficient data transmission has become a critical challenge, especially with the increasing adoption of Software-Defined Networking (SDN). Traditional network architectures struggle to address security threats such as data breaches, unauthorized access, and control-plane attacks. SDN, while offering centralized control and programmability, also introduces vulnerabilities that can be exploited by malicious actors. This research focuses on designing and implementing a secure data transmission framework that integrates SDN with advanced cryptographic techniques to mitigate these security risks. The proposed framework employs AES-256 encryption for data confidentiality, Diffie-Hellman (DH) key exchange for secure key distribution, and Transport Layer Security (TLS) for securing control-plane communication. Unlike existing approaches, this multi-layered security model enhances network resilience while maintaining optimal performance. The methodology involves developing an SDN-based network environment using the Ryu controller and Mininet emulator, implementing encryption mechanisms, and evaluating key performance metrics such as packet delivery rate, latency, and resource utilization. Experimental results demonstrate a 100% packet delivery rate, no packet loss, and an average latency of 3-5 ms. Despite the slight increase in CPU and memory utilization, the framework effectively balances security and efficiency, making it a robust solution for modern network infrastructures.

Internet of Things (IoT) is one of the most cited terms within the communication research communities. Next generation wireless networks technologies are expected to have massive-connections of tens of billions of devices. Such a huge number of devices raised a number of concerns in regards to how much accessible resources are available and what are the best technologies for managing those resources, all in order to avoid shutdowns/collapses in every means. In terms of wireless networks, and in regards to energy being the backbone of IoT devices, Low Power Wide Area Networks (LPWAN) technologies are considered to be a potential solution for IoT applications. In particular, this study reviews Long-Range (LoRa) technology and advances in the literature of LoRaWAN protocol to date. Furthermore, it discusses the challenges in LoRaWAN and diverts the attention towards applying Ultra-Dense Network concept on LPWAN.

Optimized resource allocation in distributed systems is well investigated. The inherent selfish nature of the users of a distributed LAN system results in conflict of interest among them. Thus, the situation (states of the nature) and the associated consequences can be easily modelled under non-cooperative game theoretic framework. In this paper, we model the resource utilization problem in distributed systems as a game theory problem. It has been found and showed that the number of best strategy profiles (i.e. the Nash Equilibrium) for this non-cooperative game is infinite. Therefore, canonical learning of the focal point theorem can be incorporated in this framework to obtain a unique solution.

This paper presents a case study of the 10-Gigabit Ethernet (10GbE) adapter from Intel R . Specifically, with appropriate optimizations to the configurations of the 10GbE adapter and TCP, we demonstrate that the 10GbE adapter can perform well in local-area, storage-area, system-area, and wide-area networks. For local-area, storage-area, and system-area networks in support of networks of workstations, network-attached storage, and clusters, respectively, we can achieve over 7-Gb/s end-to-end throughput and 12-µs end-to-end latency between applications running on Linux-based PCs. For the wide-area network in support of grids, we broke the recently-set Inter-net2 Land Speed Record by 2.5 times by sustaining an endto-end TCP/IP throughput of 2.38 Gb/s between Sunnyvale, California and Geneva, Switzerland (i.e.,037 kilometers) to move over a terabyte of data in less than an hour. Thus, the above results indicate that 10GbE may be a cost-effective solution across a multitude of computing environments.

In this research, with the installation of Sigfox's antenna in our university, we installed IoT equipment that makes use of the Sigfox network. As an example of an IoT device, we tried installing it on a water meter to acquire data, such as water usage fee, via internet. Also, using the system outline, we constructed it as an educational system.

Content Delivery Network (CDN) refers to a collection of servers strategically positioned across multiple geographical locations, with the primary purpose of caching content close to end users. A Content Delivery Network (CDN) facilitates the expeditious transmission of essential components for rendering digital content on the Internet, encompassing HTML pages, JavaScript files, style sheets, images, and videos. The utilization of Content Delivery Network (CDN) services is witnessing an upsurge in popularity, presently accounting for a significant proportion of web traffic, even encompassing major platforms like Facebook, Netflix, and Amazon. Due to the importance of this site, this paper will discuss the concept of CDN, and the important topics related to it related to the network, what are its types and divisions, and its importance in the world of information technology. The research analyzes the most important studies presented by researchers from 2021 to 2023.

This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Abstract This document describes an OPTIONAL extension to the Internet Printing Protocol/1.1: Model and Semantics (RFC 2911, RFC 2910). This extension allows a client to subscribe to printing related Events. Subscriptions are modeled as Subscription Objects. The Subscription Object specifies that when one of the specified Events occurs, the Printer delivers an asynchronous Event Notification to the specified Notification Recipient via the specified Push or Pull Delivery Method (i.e., protocol).

Many of today's military services and applications run on geographically distributed sites. Before these services and applications can be deployed in an actual network, they need to be tested and evaluated under realistic scenarios with many unpredictable factors. Existing experimental tools cannot meet the requirements for scale, accuracy and timeliness. A network emulation framework called ROSENET is proposed that can meet these requirements by using a remote parallel simulation server to model a wide area network and a local network emulator to provide timely QoS predictions for testing real world applications. This paper discusses the challenges faced in applying ROSENET to defense applications through two case studies. In the first case study we apply synthetic traffic workloads over DARPA's NMS network topology for a large scale simulation and define a metric called remote emulation delay to evaluate and quantify ROSENET's performance. In the second case study we illustrate the procedures using ROSENET to evaluate a contemporary real-time distributed VoIP application, Skype, and present experimental results.

High-performance wide-area networks are required to interconnect clusters of computers connected by local area and metropolitan area networks. Optical fiber technology provides long distance channels in the multigigabit per second range. The challenge is to provide switching nodes that handle these data rates with minimum delay, and at a reasonable cost. In this paper, we describe a packet-switching network with photonic data path, christened Blazenet,' that provides low delay and has minimal memory requirements. It can be extended to support multicast and priority delivery. Such a network can revolutionize the opportunities for distributed command and control, information and resources sharing, real-time conferencing, and wide-area parallel computation.

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Applications at the Army High Performance Computing Research Center's (AHPCRC) Graphics and Visualization Laboratory (GVL) at the University of Minnesota require a tremendous amount of I/O bandwidth and this appetite for data is growing. Silicon Graphics workstation are used to perform the post-processing, visualization, and animation of multi-terabyte size datasets produced by scientific simulations performed on AHPCRC supercomputers. The M.A.X. (Maximum Achievable Xfer) was designed to find the maximum achievable I/O performance of the Silicon Graphics CHALLENGE/Onyx-class machines that run these applications. Running a fully configured Onyx machine with 12 -150MHz R4400 processors, 512MB of 8-way interleaved memory, 31 fast/wide SCSI-2 channels each with a Ciprico disk array controller we were able to achieve a maximum sustained transfer rate of 509.8 megabytes per second. However, after analyzing the results it became clear that the true maximum transfer rate is somewhat beyond this figure and we will need to do further testing with more disk array controllers in order to find the true maximum. N_t_t_II%_ PA_]_ I_AN'I[ lq13¢ I_,M_,Y ) 75

In this project we look at the performance characteristics of three tools used to move large data sets over dedicated long distance networking infrastructure. Although performance studies of wide area networks have been a frequent topic of interest, performance analyses have tended to focus on network latency characteristics and peak throughput using network traffic generators. In this study we instead perform an end-to-end long distance networking analysis that includes reading large data sets from a source file system and committing large data sets to a destination file system. An evaluation of end-to-end data movement is also an evaluation of the system configurations employed and the tools used to move the data. For this paper, we have built several storage platforms and connected them with a high performance long distance network configuration. We use these systems to analyze the capabilities of three data movement tools: BBcp, GridFTP, and XDD. Our studies demonstrate that existing data movement tools do not provide efficient performance levels or exercise the storage devices in their highest performance modes. We describe the device information required to achieve high levels of I/O performance and discuss how this data is applicable in use cases beyond data movement performance.

Increasing demands on electricity supply, with the need for system economic optimization and power system growth limitations, have a significant impact on power system reliability. Because of these system demands, the power system operates closer to its stability limits. When the system operates in extreme conditions, load shedding, generation shedding, or system islanding must occur to prevent total system collapse. Typical causes of system collapse are voltage instability or transient angle instability. These instabilities can occur independently or jointly. In most cases, system wide-area disruptions begin as a voltage stability problem. Because of a failure to take proper actions for the system to recover, this voltage stability problem evolves into an angle stability problem. New monitoring, protection, and communications technologies allow us to implement economical local-and wide-area protection systems that minimize risk of wide-area system disruptions or total system collapse. This paper provides examples of actual system disruptions and historical wide-area protection system (WAPS) solutions that use such traditional approaches as underfrequency and undervoltage load shedding. The paper also presents solutions that use programmable logic capabilities, faster communications, and synchronized phasor measurements available in meters and protective relays to prevent system disruptions.

In recent years, with the rapid exhaustion of the capacity in wide area networks led by Internet and multimedia applications, demand for high bandwidth has been growing at a very fast pace. Wavelength-division multiplexing (WDM) is a promising technique for utilizing the huge available bandwidth in optical fibers. In this paper, we consider efficient designs of nonblocking WDM permutation switching networks. Such designs require nontrivial extensions from the existing designs of electronic switching networks. We first propose several permutation models in WDM switching networks ranging from no wavelength conversion, to limited wavelength conversion, to full wavelength conversion, and analyze the network performance in terms of the permutation capacity and network cost, such as the number of optical cross-connect elements and the number of wavelength converters required for each model. We then give two methods for constructing nonblocking multistage WDM switching networks to reduce the network cost.

Multi-tier architectures provide a means for building scalable distributed services. Caching is a classical technique for enhancing the performance of systems (e.g. database servers, or web servers). Although caching solutions have been successfully studied for individual tiers of multi-tier systems, if collectively applied, these solutions may violate the coherence of cached data. This paper precisely addresses this issue. It presents e-Caching, an end-to-end caching system for multi-tier services aimed at guaranteeing data consistency across caches. The paper describes a novel caching protocol to automatically detect data dependencies and apply inter-cache invalidations. The implemented protocol is evaluated with the TPC-W online multi-tier bookstore service. The evaluation shows that e-Caching improves service performance compared to regular caching techniques while guaranteeing global data consistency in multi-tier systems. Today, many applications are implemented using multi-tier architectures. Internet services, which range from Web servers to streaming media services, are based on this kind of architectures. Classical three-tier Web applications start with requests from Web clients that flow through an HTTP front-end server and provider of static content, then to an enterprise server to execute the business logic of the application and generate web pages on-the-fly, and finally to a database that stores non-ephemeral data. To face high loads in multi-tier systems, a commonly used approach is caching . Roughly speaking, caching consists in making a copy of request results for faster future reuse of these results. Current caching solutions may successfully apply at individual tiers of multi-tier systems to cache database query results , application business objects , or dynamic Web documents . Intuitively, caching back-end tier results (i.e. database query results) provides higher cache hit ratio than caching front-end tier query results, since the same back-end query may be issued and shared by different front-end queries. Whereas, caching front-end tier results offers a greater benefit in terms of service response times in case of a cache hit, since front-end caching saves time on the front-end and on the back-end. Therefore, caching solutions at these different levels are complementary and would improve the overall performance of multi-tier systems. However, if put all together, existing individual caching solutions of multi-tier systems might result in globally inconsistent cached data across tiers, in case of dynamic and inter-dependent data. The objective of this paper is to precisely bridge the gap between performance and consistency of caching in multi-tier systems as follows : -Automatic data analysis to detect inter-dependent data across caches of all tiers. -Data consistency across multi-tier cache systems by using the generated data dependencies. -Transparent caching for an easier and automated integration of caching to multi-tier systems. In this paper, we present e-Caching, an end-to-end caching system that provides consistency across cache levels. It guarantees consistency of cached data through an automatic multi-tier flow analysis. We describe a novel caching protocol that guarantees consistency of cached data through multi-tier flow

This paper describes the improvement of web cache server by scoping in replacement algorithm of data which are collected from the clients. We have found that each replacement algorithm is suitable for each type of data in the web pages. Therefore, we introduce the mechanism to select the replacement algorithm depending on the size of data called the Replacement Algorithm Selection Mechanism (RASM). RASM allows the web cache server to have the suitable replacement algorithm for each type of data. As the result, the byte hit ratio of web cache server can be increased and the congestion in the network can be alleviated.

The Internet of Things (IoT) is a groundbreaking concept that aims to establish seamless connectivity among a wide array of devices. The IoT devices has revolutionized various industries. However, the deployment of IoT devices in vulnerable environments has led to numerous security challenges, including but not limited to data privacy, device authentication, secure data transmission, and protection against malicious intrusions. Additionally, in various application domains nodes are not static, they can move across different networks and zone. This mobility introduces further security concerns, as IoT nodes encounter different threats and risk levels through the zones. Furthermore, security services must be capable of operating transparently to facilitate the continuous functioning of nodes during movement. This paper addresses the challenges and requirements that must be considered when designing solutions for IoT to secure communications while accommodating mobility. Additionally, the paper delves into adaptive security as research direction we identified to ensure security while supporting mobility for IoT.

The last decade has transformed wireless access technologies and crystallized a new direction for the internet of things (IoT). The modern low-power wide-area network (LPWAN) technologies have been introduced to deliver connectivity for billions of devices while keeping the costs and consumption low, and the range of communication high. While the 5G (fifth generation mobile network) LPWAN-like radio technologies, namely NB-IoT (narrowband internet of things) and LTE-M (long-term evolution machine type communication) are emerging, the long-range wide-area network (LoRaWAN) remains extremely popular. One unique feature of this technology, which distinguishes it from the competitors, is the possibility of supporting both public and private network deployments. In this paper we focus on this aspect and deliver original results comparing the performance of the private and public LoRAWAN deployment options; these results should help understand the LoRaWAN technology and give a clear overview of the advantages and disadvantages of the private versus public approaches. Notably, we carry the comparison along the three dimensions: the communication performance, the security, and the cost analysis. The presented results illustratively demonstrate the differences of the two deployment approaches, and thus can support selection of the most efficient deployment option for a target application.

The last decade has transformed wireless access technologies and crystallized a new direction for the internet of things (IoT). The modern low-power wide-area network (LPWAN) technologies have been introduced to deliver connectivity for billions of devices while keeping the costs and consumption low, and the range of communication high. While the 5G (fifth generation mobile network) LPWAN-like radio technologies, namely NB-IoT (narrowband internet of things) and LTE-M (long-term evolution machine type communication) are emerging, the long-range wide-area network (LoRaWAN) remains extremely popular. One unique feature of this technology, which distinguishes it from the competitors, is the possibility of supporting both public and private network deployments. In this paper we focus on this aspect and deliver original results comparing the performance of the private and public LoRAWAN deployment options; these results should help understand the LoRaWAN technology and give a clear overv...

In this paper we advocate the use of device-to-device (D2D) communications in a LoRaWAN Low Power Wide Area Network (LPWAN). After overviewing the critical features of the LoRaWAN technology, we discuss the pros and cons of enabling the D2D communications for it. Subsequently we propose a network-assisted D2D communications protocol and show its feasibility by implementing it on top of a LoRaWAN-certified commercial transceiver. The conducted experiments show the performance of the proposed D2D communications protocol and enable us to assess its performance. More precisely, we show that the D2D communications can reduce the time and energy for data transfer by 6 to 20 times compared to conventional LoRaWAN data transfer mechanisms. In addition, the use of D2D communications may have a positive effect on the network by enabling spatial re-use of the frequency resources. The proposed LoRaWAN D2D communications can be used for a wide variety of applications requiring high coverage, e.g. use cases in distributed smart grid deployments for management and trading.

The Internet of Things (IoT) devices and applications are spreading all over around us to become the cardiovascular infrastructure for the data of the cyber-physical systems of the future. The implementation of a reliable collection of telemetry data within various application domains, including medicine, safety, and security, industry, smart cities, or environmental monitoring, to name just a few, is among the major challenges still to be solved. Importantly, many of the use cases imply a huge geographic area span or operation in remote areas with limited infrastructure availability and poor reachability. To address these scenarios in this paper, we propose a combination of the two technologies the Low Power Wide Area Network (LPWAN) and the Unmanned Aerial Vehicles (UAVs). Specifically, we study the energy utility and the communication performance of introducing a UAV-based GW into an LPWAN based on the LoRaWAN technology. The results of our simulations show that a UAVbased GW enables to reduce the mean energy consumption for communication in the network by up to 59%. Depending on the UAV speed, the communication performance in terms of the packet delivery ratio can either increase or decrease by several percentage points.

The Internet of Things (IoT) devices and applications are spreading all over around us to become the cardiovascular infrastructure for the data of the cyber-physical systems of the future. The implementation of a reliable collection of telemetry data within various application domains, including medicine, safety, and security, industry, smart cities, or environmental monitoring, to name just a few, is among the major challenges still to be solved. Importantly, many of the use cases imply a huge geographic area span or operation in remote areas with limited infrastructure availability and poor reachability. To address these scenarios in this paper, we propose a combination of the two technologies the Low Power Wide Area Network (LPWAN) and the Unmanned Aerial Vehicles (UAVs). Specifically, we study the energy utility and the communication performance of introducing a UAV-based GW into an LPWAN based on the LoRaWAN technology. The results of our simulations show that a UAVbased GW enables to reduce the mean energy consumption for communication in the network by up to 59%. Depending on the UAV speed, the communication performance in terms of the packet delivery ratio can either increase or decrease by several percentage points.