Evolutionary optical framework - NG-PON2: controlo e sincronização de ONUs via ICTP (Inter- Channel-Termination Protocol)

The study of new technologies with the potential to support high transfer rates is important to respond to the constant evolution of Internet information consumption. The Next-Generation Passive Optical Networks (NG-PON) tries to overcome this obstacle. The most recent one, NG-PON2, uses several channels in the same fiber to transmit and receive data, considerably increasing the bandwidth of a single fiber. This new form of communication has introduced a new problem, the exchange of information between these channels with a minimum of disturbances on the network. The Inter-Channel-Termination Protocol (ICTP) was presented to certify that this communication is done correctly in a multi-operator environment. Based on a pre-built environment with the cooperative use of Gigabit PON (GPON) and NG-PON2 technologies, a system with similar characteristics to those of a real scenario was developed. In this system, two ICTP use cases were implemented and, for each one, two events were tested. The results obtained showed the possibility of being used in a real scenario, without failures and with small delays.O estudo de novas tecnologias com potencial para suportar taxas de transferência elevadas é importante para dar resposta à constante evolução do consumo de informação da Internet. As Redes Óticas Passivas de Próxima Geração (NG-PON) vêm tentar ultrapassar este obstáculo. A mais recente, NGPON2, utiliza vários canais na mesma fibra para transmitir e receber dados, aumentando consideravelmente a largura de banda de uma única fibra. Esta nova forma de comunicação veio a introduzir um novo problema: a troca de informação entre estes canais com o mínimo de distúrbios na rede. O Protocolo Inter-Channel-Termination (ICTP) foi apresentado para certificar que esta comunicação é feita corretamente num ambiente de vários operadores. Baseado num ambiente pré-construído com o uso simultâneo das tecnologias Gigabit PON (GPON) e NG-PON2, foi desenvolvido um sistema com características semelhantes às de um cenário real. Neste sistema, foram implementados dois casos de uso do ICTP e, para cada um, testaram-se dois eventos. Os resultados obtidos mostraram a possibilidade de serem usados num cenário real, sem falhas e com atrasos reduzidos.Mestrado em Engenharia de Computadores e Telemátic

Bounded Protocols for Efficient Reliable Message Transmission

In the reliable message transmission problem (RMTP) processors communicate by exchanging messages, but the channel that connects two processors is subject to message loss, duplication, and reordering. Previous work focused on proposing protocols in asynchronous systems, where message size is finite and sequence numbers are bounded. However, if the channel can duplicate messages, lose messages, and arbitrarily reorder the messages, the problem is unsolvable. In this thesis, we consider a strengthening of the asynchronous model in which reordering of messages is bounded. In this model, we develop two efficient protocols to solve the RMTP: (1) when messages may be duplicated but not lost and (2) when messages may be duplicated and lost. This result is in contrast to the impossibility of such an algorithm when reordering is unbounded. Our protocols have the pleasing property that no messages need to be sent from the receiver to the sender

Simulation of packet and cell-based communication networks

This thesis investigates, using simulation techniques, the practical aspects of implementing a novel mobility protocol on the emerging Broadband Integrated Services Digital Network standard. The increasing expansion of telecommunications networks has meant that the demand for simulation has increased rapidly in recent years; but conventional simulators are slow and developments in the communications field are outstripping the ability of sequential uni-processor simulators. Newer techniques using distributed simulation on a multi-processor network are investigated in an attempt to make a cell-level simulation of a non-trivial B.-I.S.D.N. network feasible. The current state of development of the Asynchronous Transfer Mode standard, which will be used to implement a B.-I.S.D.N., is reviewed and simulation studies of the Orwell Slotted Ring protocol were made in an attempt to devise a simpler model for use in the main simulator. The mobility protocol, which uses a footprinting technique to simplify hand- offs by distributing information about a connexion to surrounding base stations, was implemented on the simulator and found to be functional after a few 'special case' scenarios had been catered for

DistriX : an implementation of UNIX on transputers

Bibliography: pages 104-110.Two technologies, distributed operating systems and UNIX are very relevant in computing today. Many distributed systems have been produced and many are under development. To a large extent, distributed systems are considered to be the only way to solve the computing needs of the future. UNIX, on the other hand, is becoming widely recognized as the industry standard for operating systems. The transputer, unlike. UNIX and distributed systems is a relatively new innovation. The transputer is a concurrent processing machine based on mathematical principles. Increasingly, the transputer is being used to solve a wide range of problems of a parallel nature. This thesis combines these three aspects in creating a distributed implementation of UNIX on a network of transputers. The design is based on the satellite model. In this model a central controlling processor is surrounded by worker processors, called satellites, in a master/ slave relationship

A Survey on Wireless Security: Technical Challenges, Recent Advances and Future Trends

This paper examines the security vulnerabilities and threats imposed by the inherent open nature of wireless communications and to devise efficient defense mechanisms for improving the wireless network security. We first summarize the security requirements of wireless networks, including their authenticity, confidentiality, integrity and availability issues. Next, a comprehensive overview of security attacks encountered in wireless networks is presented in view of the network protocol architecture, where the potential security threats are discussed at each protocol layer. We also provide a survey of the existing security protocols and algorithms that are adopted in the existing wireless network standards, such as the Bluetooth, Wi-Fi, WiMAX, and the long-term evolution (LTE) systems. Then, we discuss the state-of-the-art in physical-layer security, which is an emerging technique of securing the open communications environment against eavesdropping attacks at the physical layer. We also introduce the family of various jamming attacks and their counter-measures, including the constant jammer, intermittent jammer, reactive jammer, adaptive jammer and intelligent jammer. Additionally, we discuss the integration of physical-layer security into existing authentication and cryptography mechanisms for further securing wireless networks. Finally, some technical challenges which remain unresolved at the time of writing are summarized and the future trends in wireless security are discussed.Comment: 36 pages. Accepted to Appear in Proceedings of the IEEE, 201

Modelling a Distributed Data Acquisition System

This thesis discusses the formal modelling and verification of certain non-real-time aspects of correctness of a mission-critical distributed software system known as the ALICE Data Point Service (ADAPOS). The domain of this distributed system is data acquisition from a particle detector control system in experimental high energy particle physics research. ADAPOS is part of the upgrade effort of A Large Ion Collider Experiment (ALICE) at the European Organisation for Nuclear Research (CERN), near Geneva in France/Switzerland, for the third run of the Large Hadron Collider (LHC). ADAPOS is based on the publicly available ALICE Data Point Processing (ADAPRO) C++14 framework and works within the free and open source GNU/Linux ecosystem. The model checker Spin was chosen for modelling and verifying ADAPOS. The model focuses on the general specification of ADAPOS. It includes ADAPOS processes, a load generator process, and rudimentary interpretations for the network protocols used between the processes. For experimenting with different interpretations of the underlying network protocols and also for coping with the state space explosion problem, eight variants of the model were developed and studied. Nine Linear Temporal Logic (LTL) properties were defined for all those variants. Large numbers of states were covered during model checking even though the model turned out to have a reachable state space too large to fully exhaust. No counter-examples were found to safety properties. A significant amount of evidence hinting that ADAPOS seems to be safe, was obtained. Liveness properties and implementation-level verification among other possible research directions remain open