A survey on Routing Protocols in Wireless Sensor Networks

In ad-hoc WSN is a collection of mobile nodes that are dynamically and randomly located in such a manner that the interconnections between nodes are changing on a continual basis. The dynamic nature of these networks demands new set of network routing strategy protocols to be implemented in order to provide efficient end-to end communication. Moreover, such issues are very critical due to severe resource constraints like efficient energy utilization, lifetime of network, and drastic environmental conditions in WSNs. Neither hop-by-hop nor neither direct reach ability is possible in case of WSNs. In order to facilitate communication within the network, a routing protocol is used. In this paper we have carried out an extensive survey on WSN protocols based on structure of network, routing protocol of network & clustering techniques of routing protocols

Chainspace: A Sharded Smart Contracts Platform

Chainspace is a decentralized infrastructure, known as a distributed ledger, that supports user defined smart contracts and executes user-supplied transactions on their objects. The correct execution of smart contract transactions is verifiable by all. The system is scalable, by sharding state and the execution of transactions, and using S-BAC, a distributed commit protocol, to guarantee consistency. Chainspace is secure against subsets of nodes trying to compromise its integrity or availability properties through Byzantine Fault Tolerance (BFT), and extremely high-auditability, non-repudiation and `blockchain' techniques. Even when BFT fails, auditing mechanisms are in place to trace malicious participants. We present the design, rationale, and details of Chainspace; we argue through evaluating an implementation of the system about its scaling and other features; we illustrate a number of privacy-friendly smart contracts for smart metering, polling and banking and measure their performance

Fast and Scalable Total Order Broadcast for Wide-area Networks

Version submitted to IEEE TPDSFault tolerant protocols such as Total Order Broadcast are key aspects on the development of reliable distributed systems, but they are barely supported on large-scale systems due to the cost of traditional techniques. This paper revisits a class of Total Order Broadcast protocols called moving sequencer, known by its communication efficiency. Indeed, we evaluate RBP, one of the most known implementations of moving sequencer protocols. We demonstrate how RBP can be used with wide-area systems, and we propose new techiques to improve its resiliency and consistency properties under failures, as well as improving its scalability aspects

The Scalability of Multicast Communication

Multicast is a communication method which operates on groups of applications. Having multiple instances of an application which are addressed collectively using a unique, multicast address, allows elegant solutions to some of the more intractable problems in distributed programming, such as providing fault tolerance. However, as multicast techniques are applied in areas such as distributed operating systems, where the operating system may span a large number of hosts, or on faster network architectures, where the problems of congestion reduce the effectiveness of the technique, then the scalability of multicast must be addressed if multicast is to gain a wider application. The main scalability issue was considered to be packet loss due to buffer overrun, the most common cause of this buffer overrun being the mismatch in packet arrival rate and packet consumption at the multicast originator, the so-called implosion problem. This issue affects positively acknowledged and transactional protocols. As these two techniques are the most common protocol designs, it was felt that an investigation into the problems of these types of protocol would be most effective. A model for implosion was developed which was simulated in order to investigate the parameters of implosion. A measure of this implosion was derived from the data, this index of implosion allowing the severity of implosion to be described as well as the location of the implosion in the model. This implosion index was derived by dividing the rate at which buffers were occupied by the rate at which packets were generated by the model. The value may then be used to predict the number of buffers required given the number of packets expected. A number of techniques were developed which may be used to offset implosion, either by artificially increasing the inter-packet gap, or by distributing replies so that no one host receives enough packets to cause an implosion. Of these alternatives, the latter offers the most promise, although requiring a large effort to maintain the resulting hierarchical structure in the presence of multiple failures

A survey on Routing Protocols in Wireless Sensor Networks

In ad-hoc WSN is a collection of mobile nodes that are dynamically and randomly located in such a manner that the interconnections between nodes are changing on a continual basis. The dynamic nature of these networks demands new set of network routing strategy protocols to be implemented in order to provide efficient end-to end communication.  Moreover, such issues are very critical due to severe resource constraints like efficient energy utilization, lifetime of network, and drastic environmental conditions in WSNs. Neither hop-by-hop nor neither direct reach ability is possible in case of WSNs. In order to facilitate communication within the network, a routing protocol is used. In this paper we have carried out an extensive survey on WSN protocols based on structure of network, routing protocol of network & clustering techniques of routing protocols

Agreement-related problems:from semi-passive replication to totally ordered broadcast

Agreement problems constitute a fundamental class of problems in the context of distributed systems. All agreement problems follow a common pattern: all processes must agree on some common decision, the nature of which depends on the specific problem. This dissertation mainly focuses on three important agreements problems: Replication, Total Order Broadcast, and Consensus. Replication is a common means to introduce redundancy in a system, in order to improve its availability. A replicated server is a server that is composed of multiple copies so that, if one copy fails, the other copies can still provide the service. Each copy of the server is called a replica. The replicas must all evolve in manner that is consistent with the other replicas. Hence, updating the replicated server requires that every replica agrees on the set of modifications to carry over. There are two principal replication schemes to ensure this consistency: active replication and passive replication. In Total Order Broadcast, processes broadcast messages to all processes. However, all messages must be delivered in the same order. Also, if one process delivers a message m, then all correct processes must eventually deliver m. The problem of Consensus gives an abstraction to most other agreement problems. All processes initiate a Consensus by proposing a value. Then, all processes must eventually decide the same value v that must be one of the proposed values. These agreement problems are closely related to each other. For instance, Chandra and Toueg [CT96] show that Total Order Broadcast and Consensus are equivalent problems. In addition, Lamport [Lam78] and Schneider [Sch90] show that active replication needs Total Order Broadcast. As a result, active replication is also closely related to the Consensus problem. The first contribution of this dissertation is the definition of the semi-passive replication technique. Semi-passive replication is a passive replication scheme based on a variant of Consensus (called Lazy Consensus and also defined here). From a conceptual point of view, the result is important as it helps to clarify the relation between passive replication and the Consensus problem. In practice, this makes it possible to design systems that react more quickly to failures. The problem of Total Order Broadcast is well-known in the field of distributed systems and algorithms. In fact, there have been already more than fifty algorithms published on the problem so far. Although quite similar, it is difficult to compare these algorithms as they often differ with respect to their actual properties, assumptions, and objectives. The second main contribution of this dissertation is to define five classes of total order broadcast algorithms, and to relate existing algorithms to those classes. The third contribution of this dissertation is to compare the expected performance of the various classes of total order broadcast algorithms. To achieve this goal, we define a set of metrics to predict the performance of distributed algorithms

Mobile Ad-Hoc Networks

Being infrastructure-less and without central administration control, wireless ad-hoc networking is playing a more and more important role in extending the coverage of traditional wireless infrastructure (cellular networks, wireless LAN, etc). This book includes state-of-the-art techniques and solutions for wireless ad-hoc networks. It focuses on the following topics in ad-hoc networks: quality-of-service and video communication, routing protocol and cross-layer design. A few interesting problems about security and delay-tolerant networks are also discussed. This book is targeted to provide network engineers and researchers with design guidelines for large scale wireless ad hoc networks

Parallel and Distributed Simulation of Discrete Event Systems

The achievements attained in accelerating the simulation of the dynamics of complex discrete event systems using parallel or distributed multiprocessing environments are comprehensively presented. While parallel discrete event simulation (DES) governs the evolution of the system over simulated time in an iterative SIMD way, distributed DES tries to spatially decompose the event structure underlying the system, and executes event occurrences in spatial subregions by logical processes (LPs) usually assigned to different (physical) processing elements. Synchronization protocols are necessary in this approach to avoid timing inconsistencies and to guarantee the preservation of event causalities across LPs. Included in the survey are discussions on the sources and levels of parallelism, synchronous vs. asynchronous simulation and principles of LP simulation. In the context of conservative LP simulation (Chandy/Misra/Bryant) deadlock avoidance and deadlock detection/recovery strategies, Conservative Time Windows and the Carrier Nullmessage protocol are presented. Related to optimistic LP simulation (Time Warp), Optimistic Time Windows, memory management, GVT computation, probabilistic optimism control and adaptive schemes are investigated. (Also cross-referenced as UMIACS-TR-94-100

Crypto Assets for Wealth Management: an Analysis of the Financial System and Private Bankers' Clientele

We have already started experiencing the transformations brought by the Fourth Industrial Revolution, characterized by breakthroughs in the digital, physical and biological fields occurring in an exponential speed. This new chapter brings complex advances and innovations, which not only show evolution in the production system, but are merging in a promising way for maximizing our quality of life and creating opportunities of universal impact for authorities, managers, leaders, and citizens of all backgrounds. In the set of key technological innovations, projects challenging the traditional economic model are emerging fast, with their essence being Bitcoin and its underlying network, blockchain. The objective was to analyze the feasibility of their implementation, investment ideas and consumer adoption, based on their performance, reliability, risks, and legal compliance. A qualitative approach was conducted as a mono method. Data was collected through archival research, action research and grounded theory, aimed at finding definitions for the Bitcoin and blockchain related concepts, as well as their industry, latest updates, and policy making. The same strategies were followed for describing the market demand and consumer approaching dynamics. The outcome reflects mostly upsides on the performance of Bitcoin in recent times, though indicating that it is not a safe haven asset and that immediate applicability is not a prospect, whereas future implementation could be practical in various levels of the financial system. The technologies’ promising future suggests a positive scenario for investments now, being taken into account the contemplation of their high-risk nature. The discussion and future recommendations include exploring outside-in marketing approach strategies