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Publicações

2019

Improving ns-3 emulation performance for fast prototyping of routing and SDN protocols: Moving data plane operations to outside of ns-3

Autores
Fontes, H; Cardoso, T; Campos, R; Ricardo, M;

Publicação
SIMULATION MODELLING PRACTICE AND THEORY

Abstract
A common problem in networking research and development is the duplicate effort of writing simulation and implementation code of routing protocols. This can be avoided by reusing simulation code in real prototyping and in production environments. In ns-3, emulation mode can be used to run simulation models of routing and Software Defined Networking (SDN) protocols on top of real L2 interfaces such as Ethernet and Wi-Fi. Although this feature is already available, the additional packet processing involved degrades the performance of the nodes and limits the amount of network traffic that can be processed. Our proposal to overcome this performance bottleneck consists in moving the data plane processing operations to outside of the ns-3 process, running such operations natively in the host Operating System (OS). Two approaches are proposed: (a) running the data plane in user space (DPU); (b) running the data plane in kernel space (DPK). Both approaches support the emulation of one or multiple nodes per emulation host machine. The experimental results show that the DPU and DPK approaches significantly improve the throughput by respectively 4.9 and 19 times when compared against traditional ns-3 emulation of a single node. For multiple nodes, the DPK approach further improves the throughput by as much as 23 times. The amount of code reuse is high - e.g., for the routing protocols used in this paper, only 1.4% and 11% of extra code is required to benefit from the performance improvements achieved respectively by the DPK and DPU approaches.

2019

Reputation based approach for improved fairness and robustness in P2P protocols

Autores
Nwebonyi, FN; Martins, R; Correia, ME;

Publicação
PEER-TO-PEER NETWORKING AND APPLICATIONS

Abstract
Peer-to-Peer (P2P) overlay networks have gained popularity due to their robustness, cost advantage, network efficiency and openness. Unfortunately, the same properties that foster their success, also make them prone to several attacks. To mitigate these attacks, several scalable security mechanisms which are based on the concepts of trust and reputation have been proposed. These proposed methods tend to ignore some core practical requirements that are essential to make them more useful in the real world. Some of such requirements include efficient bootstrapping of each newcomer's reputation, and mitigating seeder(s) exploitation. Additionally, although interaction among participating peers is usually the bases for reputation, the importance given to the frequency of interaction between the peers is often minimized or ignored. This can result in situations where barely known peers end-up having similar trust scores to the well-known and consistently cooperative nodes. After a careful review of the literature, this work proposes a novel and scalable reputation based security mechanism that addresses the aforementioned problems. The new method offers more efficient reputation bootstrapping, mitigation of bandwidth attack and better management of interaction rate, which further leads to improved fairness. To evaluate its performance, the new reputation model has been implemented as an extension of the BitTorrent protocol. Its robustness was tested by exposing it to popular malicious behaviors in a series of extensive PeerSim simulations. Results show that the proposed method is very robust and can efficiently mitigate popular attacks on P2P overlay networks.

2019

3D Simulator with Hardware-in-the-Loop capability for the Micromouse Competition

Autores
Piardi, L; Eckert, L; Lima, J; Costa, P; Valente, A; Nakano, A;

Publicação
2019 19TH IEEE INTERNATIONAL CONFERENCE ON AUTONOMOUS ROBOT SYSTEMS AND COMPETITIONS (ICARSC 2019)

Abstract
Robotics competitions are a way to challenge researchers, roboticists and enthusiastic to address robot applications. One of the well-known international competition is the Micromouse where the fastest mobile robot to solve a maze is the winner. There are several topics addressed in this competition such as robot prototyping, control, electronics, path planning, optimization, among others while keeping the size of the robot as small as possible. A simulation can be used to speed-up the development and testing algorithms but faces the gap between a simulation and reality, specially in the dynamics behaviour. There are some simulation environments that allow to simulate the Micromouse competition, but in this paper, an Hardware-in-the-loop simulator tool is presented where the simulated robot is controlled by the same microcontroller used by the robot. By this way, the developed algorithms are tested and validated with the limitations and constraints presented in the real hardware, such as memory and processing capabilities. The robot dynamics, the slippage of the wheels, the friction and the 3D visualization are present in the simulator. The presented results show that the same code and hardware controlling the simulated and the real robot identically.

2019

Investigation on the Relation between the Level of Wind and PV Generation and the Contracted and Mobilized FRR and RR Reserves in Portugal

Autores
Barrias, G; Saraiva, JT;

Publicação
2019 16TH INTERNATIONAL CONFERENCE ON THE EUROPEAN ENERGY MARKET (EEM)

Abstract
The Portuguese generation system includes a large amount of wind parks plus a rapidly increasing capacity in PV units. These units as well as some other technologies are classified as Special Regime Generation, SRG, and are paid feed in tariffs. The operation planning for the next day is based on estimates of these injections made in the morning of the day before operation. Then on the operation day, the wind and PV generations will likely be different originating the activation of reserves, namely automatic Frequency Restoration Reserve, aFRR, and Replacement Reserve, RR. Therefore, the main purpose of this paper is to report the research that was conducted to check whether the large amount of wind and PV capacities explain the amounts of contracted and mobilized aFRR and RR reserves. To do this we used data for 2016 publicly available on the web page of the Portuguese TSO. The clarification of this issue is relevant because the amount of money required to pay reserves has been increasing in recent years and this amount is internalized in the Access Tariffs paid by all Portuguese consumers.

2019

Enhancing the ns-3 simulator by introducing Electric Vehicles features

Autores
Sanguesa, JA; Salvatella, S; Martinez, FJ; Marquez Barja, JM; Ricardo, MP;

Publicação
2019 28TH INTERNATIONAL CONFERENCE ON COMPUTER COMMUNICATION AND NETWORKS (ICCCN)

Abstract
Electric Vehicles (EVs) sales are increasing in the recent years due to several factors such as cost reduction, fuel cost increase, pollution reductions, government incentives, among others. At the same time, Intelligent Transportation Systems (ITS) are continuously improving, and researchers use different simulators in order to test their proposals before implementing them in real devices. However, traditional communications-aimed simulations do not include fuel consumption issues that are a key factor in transportation systems. This paper presents the addition of Electric Vehicles consumption to the ns-3 simulator, which currently is one of the most used network simulators. Our proposal follows all the models, coding style, as well as engineering guidelines of ns-3, coupled with the characteristics of each vehicle, to accurately estimate the energy consumption. We also analyze the performance of our proposal while simulating a part of the E313 highway, located in Antwerp, Belgium. In particular, we compare the ns-3 results obtained in terms of energy consumption to those obtained in SUMO. In addition, we study the impact of our proposal on the overall simulation time.

2019

Applicability study os the oedometer test to a silty sand

Autores
Paula, António Miguel; Gonçalves, José; Batista, José; Braz-César, Manuel; Freitas, Bruno Afonso;

Publicação
INTERNATIONAL CONGRESS ON ENGINEERING UNIVERSITY OF BEIRA INTERIOR – ENGINEERING FOR EVOLUTION 2019

Abstract
This paper exposes the applicability study of the oedometer test to an existing silty sand soil, from the city of Braganza, with the purpose to verify the applicability of this test to soils with fines in his composition, in a region with predominance of granite residual soils, considering that the granulometric curve of these soils are substantially different from the granulometric curves of the soils that are usually tested. For this, two types of soils were collected, namely intact samples of a silty sand, and a disturbed soil sample whose grains size distribution curve built into laboratory corresponds to a high plasticity silt. Due to the greater predominance of fines in the high plasticity silt, the mechanical behaviour of this soil, more conditioned by forces of an electrochemical nature, serves as a comparative term to the mechanical behaviour of the undisturbed samples of the silty sand, with a behaviour less dependent on these forces, thus allowing to show applicability of the test to soils with lower percentage of fines, with a more pronounced gravitational behaviour and, therefore, more atypical to the oedometer test. From the results obtained for silty sand, a high value of the immediate settlement was verified after each applied load cycle. Thus this observation, the beginning of the consolidation process demands high accurate recording of the settlement that clearly identify the time that primary consolidation begins. In this way, the implementation of the data acquisition system, allowing the correct reading of the consolidation beginning, minimizing human errors, expands the spectrum of soils existing in the region that can be study by the consolidation problematics point of view.

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