A Peer-to-Peer Approach to Content-Based Publish/Subscribe

Publish/subscribe systems are successfully used to decouple distributed applications. However, their e#ciency is closely tied to the topology of the underlying network, the design of which has been neglected. Peer-to-peer network topologies can o#er inherently bounded delivery depth, load sharing, and self-organisation. In this paper, we present a contentbased publish/subscribe system routed over a peer-to-peer topology graph. The implications of combining these approaches are explored and a particular implementation using elements from Rebeca and Chord is proven correct

Real-Time QoS-Aware Vehicle Tracking: An Experimental and Comparative Study

AbstractRecently, web service became popular for Real-time Communication (RTC). It allows bi-directional, real-time communication between web clients and server. On the other hand, Data Distribution Service (DDS) middleware offers unified integration with high-performance due to its scalability, flexibility, real-time, mission-critical networks and rich QoS features. DDS is based on the publish/subscribe communication model. It improves RTC through its efficient and high-performance data delivery mechanism. This paper studies and investigates that how DDS is better for RTC. Experimental studies are conducted to compare text messaging using socket IO over DDS Web API. The result concerns the throughput satisfaction rate, round trip time and packet loss. In addition, we consider some of QoS of DDS during experimental work e.g. deadline, time based filter etc

Discreet - Pub/Sub for Edge Systems

The number of devices connected to the Internet has been growing exponentially over the last few years. Today, the amount of information available to users has reached a point that makes it impossible to consume it all, showing that we need better ways to filter what kind of information is sent our way. At the same time, while users are online and access all this information, their actions are also being collected, scrutinized and commercialized with little regard for privacy. This thesis addresses those issues in the context of a decentralized Publish/Subscribe solution for edge systems. Working at the edge of the Internet aims to prevent centralized control from a single entity and lessen the chance of abuse. Our goal was to devise a solution that achieves efficient message delivery, with good load-balancing properties, without revealing its participants subscription interests to preserve user privacy. Our solution uses cryptography and probabilistic data sets as a way to obfuscate event topics and user subscriptions. We modeled a cooperative solution, where publisher and subscriber nodes work in concert to route events among themselves, by leveraging a onehop structured overlay. By using an experimental evaluation, we attest the scalability and general performance of the proposed algorithms, including latency, false negative and false positive rates, and other useful metrics.O número de aparelhos ligados a Internet têm vindo a crescer exponencialmente ao longo dos últimos anos. Hoje em dia, a quantidade de informação que os utilizadores têm disponível, chegou a um ponto que torna impossível o seu total consumo. Isto leva a que seja necessário encontrarmos melhores formas de filtrar a informação que recebemos. Ao mesmo tempo, as ações do utilizadores estão a ser recolhidas, examinadas e comercializadas, sem qualquer respeito pela privacidade. Esta tese trata destes assuntos no contexto de um sistema Publish/Subscribe descentralizado, para sistemas na periferia. O objectivo de operar na preferia da Internet está em prevenir o controlo centralizado por uma única entidade e diminuir a oportunidade para abusos. O nosso objectivo foi conceber uma solução que realiza entrega de mensagens eficientemente, com boas propriedades na distribuição de carga e sem revelar on interesses dos participantes, de forma a preservar a sua privacidade. A nossa solução usa criptografia e estruturas de dados probabilísticas, como uma forma de ofuscar os tópicos dos eventos e as subscrições dos utilizadores. Modelamos o sistema com o objectivo de ser uma solução cooperativa, onde ambos os tipos de nós Editores e Assinantes trabalham em concertadamente para encaminhar eventos entre eles, ao fazerem uso de uma estrutura de rede sobreposta com um salto. Fazendo uma avaliação experimental testámos a escalabilidade e o desempenho geral dos algoritmos propostos, incluindo a latência, falsos negativos, falsos positivos e outras métricas úteis

Addressing TCAM limitations in an SDN-based pub/sub system

Content-based publish/subscribe is a popular paradigm that enables asynchronous exchange of events between decoupled applications that is practiced in a wide range of domains. Hence, extensive research has been conducted in the area of efficient large-scale pub/sub system. A more recent development are content-based pub/sub systems that utilize software-defined networking (SDN) in order to implement event-filtering in the network layer. By installing content-filters in the ternary content-addressable memory (TCAM) of switches, these systems are able to achieve event filtering and forwarding at line-rate performance. While offering great performance, TCAM is also expensive, power hunger and limited in size. However, current SDN-based pub/sub systems don't address these limitations, thus using TCAM excessively. Therefore, this thesis provides techniques for constraining TCAM usage in such systems. The proposed methods enforce concrete flow limits without dropping any events by selectively merging content-filters into more coarse granular filters. The proposed algorithms leverage information about filter properties, traffic statistics, event distribution and global filter state in order to minimize the increase of unnecessary traffic introduced through merges. The proposed approach is twofold. A local enforcement algorithm ensures that the flow limit of a particular switch is never violated. This local approach is complemented by a periodically executed global optimization algorithm that tries to find a flow configuration on all switches, which minimized to increase in unnecessary traffic, given the current set of advertisements and subscriptions. For both classes, two algorithms with different properties are outlined. The proposed algorithms are integrated into the PLEROMA middleware and evaluated thoroughly in a real SDN testbed as well as in a large-scale network emulation. The evaluations demonstrate the effectiveness of the approaches under diverse and realistic workloads. In some cases, reducing the number of flows by more than 70% while increasing the false positive rate by less than 1% is possible

Dynamic Detection and Tracking of Composite Events in Wireless Sensor Networks

In questa tesi si presenta un sistema (MaD-WiSe) per la gestione efficiente di dati in reti di sensori senza fili (WSN) in scenari statici, e si forniscono diverse tecniche di ottimizzazione validate da risultati sperimentali su una rete di sensori reale. Si presenta inoltre un nuovo linguaggio dichiarativo (EQL) per esprimere eventi compositi da rilevare e tracciare in modo dinamico e autonomo e si fornisce uno schema di implementazione e un simulatore per la valutazione delle performance

High-performance and fault-tolerant techniques for massive data distribution in online communities

The amount of digital information produced and consumed is increasing each day. This rapid growth is motivated by the advances in computing power, hardware technologies, and the popularization of user generated content networks. New hardware is able to process larger quantities of data, which permits to obtain finer results, and as a consequence more data is generated. In this respect, scientific applications have evolved benefiting from the new hardware capabilities. This type of application is characterized by requiring large amounts of information as input, generating a significant amount of intermediate data resulting in large files. This increase not only appears in terms of volume, but also in terms of size, we need to provide methods that permit a efficient and reliable data access mechanism. Producing such a method is a challenging task due to the amount of aspects involved. However, we can leverage the knowledge found in social networks to improve the distribution process. In this respect, the advent of the Web 2.0 has popularized the concept of social network, which provides valuable knowledge about the relationships among users, and the users with the data. However, extracting the knowledge and defining ways to actively use it to increase the performance of a system remains an open research direction. Additionally, we must also take into account other existing limitations. In particular, the interconnection between different elements of the system is one of the key aspects. The availability of new technologies such as the mass-production of multicore chips, large storage media, better sensors, etc. contributed to the increase of data being produced. However, the underlying interconnection technologies have not improved with the same speed as the others. This leads to a situation where vast amounts of data can be produced and need to be consumed by a large number of geographically distributed users, but the interconnection between both ends does not match the required needs. In this thesis, we address the problem of efficient and reliable data distribution in a geographically distributed systems. In this respect, we focus on providing a solution that 1) optimizes the use of existing resources, 2) does not requires changes in the underlying interconnection, and 3) provides fault-tolerant capabilities. In order to achieve this objectives, we define a generic data distribution architecture composed of three main components: community detection module, transfer scheduling module, and distribution controller. The community detection module leverages the information found in the social network formed by the users requesting files and produces a set of virtual communities grouping entities with similar interests. The transfer scheduling module permits to produce a plan to efficiently distribute all requested files improving resource utilization. For this purpose, we model the distribution problem using linear programming and offer a method to permit a distributed solving of the problem. Finally, the distribution controller manages the distribution process using the aforementioned schedule, controls the available server infrastructure, and launches new on-demand resources when necessary