Social Network Analysis

The Internet has led to the creation of a digital society, where (almost) everything is connected and is accessible from anywhere. However, despite their widespread adoption, traditional IP networks are complex and very hard to manage. It is both difficult to configure the network according to predefined policies, and to reconfigure it to respond to faults, load, and changes. To make matters even more difficult, current networks are also vertically integrated: the control and data planes are bundled together. Software-defined networking (SDN) is an emerging paradigm that promises to change this state of affairs, by breaking vertical integration, separating the network's control logic from the underlying routers and switches, promoting (logical) centralization of network control, and introducing the ability to program the network. The separation of concerns, introduced between the definition of network policies, their implementation in switching hardware, and the forwarding of traffic, is key to the desired flexibility: by breaking the network control problem into tractable pieces, SDN makes it easier to create and introduce new abstractions in networking, simplifying network management and facilitating network evolution. In this paper, we present a comprehensive survey on SDN. We start by introducing the motivation for SDN, explain its main concepts and how it differs from traditional networking, its roots, and the standardization activities regarding this novel paradigm. Next, we present the key building blocks of an SDN infrastructure using a bottom-up, layered approach. We provide an in-depth analysis of the hardware infrastructure, southbound and northbound application programming interfaces (APIs), network virtualization layers, network operating systems (SDN controllers), network programming languages, and network applications. We also look at cross-layer problems such as debugging and troubleshooting. In an effort to anticipate the future evolution of this new paradigm, we discuss the main ongoing research efforts and challenges of SDN. In particular, we address the design of switches and control platforms—with a focus on aspects such as resiliency, scalability, performance, security, and dependability—as well as new opportunities for carrier transport networks and cloud providers. Last but not least, we analyze the position of SDN as a key enabler of a software-defined environment.

https://publications.uni.lu/bitstream/10993/20596/1/survey_on_SDN.pdf

Software-Defined Networking: A Comprehensive Survey

National Institute of Standards and Technology における超伝導研究及び生活

What is modal logic

Software-Defined Networking (SDN) is an emerging paradigm that promises to change this state of affairs, by breaking vertical integration, separating the network's control logic from the underlying routers and switches, promoting (logical) centralization of network control, and introducing the ability to program the network. The separation of concerns introduced between the definition of network policies, their implementation in switching hardware, and the forwarding of traffic, is key to the desired flexibility: by breaking the network control problem into tractable pieces, SDN makes it easier to create and introduce new abstractions in networking, simplifying network management and facilitating network evolution. In this paper we present a comprehensive survey on SDN. We start by introducing the motivation for SDN, explain its main concepts and how it differs from traditional networking, its roots, and the standardization activities regarding this novel paradigm. Next, we present the key building blocks of an SDN infrastructure using a bottom-up, layered approach. We provide an in-depth analysis of the hardware infrastructure, southbound and northbound APIs, network virtualization layers, network operating systems (SDN controllers), network programming languages, and network applications. We also look at cross-layer problems such as debugging and troubleshooting. In an effort to anticipate the future evolution of this new paradigm, we discuss the main ongoing research efforts and challenges of SDN. In particular, we address the design of switches and control platforms -- with a focus on aspects such as resiliency, scalability, performance, security and dependability -- as well as new opportunities for carrier transport networks and cloud providers. Last but not least, we analyze the position of SDN as a key enabler of a software-defined environment.

Coverage path planning consists of finding the route which covers every point of a certain area of interest. In recent times, Unmanned Aerial Vehicles (UAVs) have been employed in several application domains involving terrain coverage, such as surveillance, smart farming, photogrammetry, disaster management, civil security, and wildfire tracking, among others. This paper aims to explore and analyze the existing studies in the literature related to the different approaches employed in coverage path planning problems, especially those using UAVs. We address simple geometric flight patterns and more complex grid-based solutions considering full and partial information about the area of interest. The surveyed coverage approaches are classified according to a classical taxonomy, such as no decomposition, exact cellular decomposition, and approximate cellular decomposition. This review also contemplates different shapes of the area of interest, such as rectangular, concave and convex polygons. The performance metrics usually applied to evaluate the success of the coverage missions are also presented.

Survey on Coverage Path Planning with Unmanned Aerial Vehicles

Most organizations use several security policies to control different systems and data, comprising in this way a global complex policy. These security policies are often scattered over different environments, each one with its own security model and domain of administration, making them difficult to administer and understand. Moreover, some applications (e.g. workflow), often need to cross several of these security domains and satisfy each one of their policies, which is very difficult to accomplish when these policies are scattered over the organization, in conflict with each other and frequently expressed in differ-

/pdf/spl-an-access-control-language-for-security-policies-and-u7ye1363ts.pdf

SPL: An Access Control Language for Security Policies and Complex Constraints.

Most unmanned aerial vehicles nowadays engage in coverage missions using simple patterns, such as back-and-forth and spiral. However, there is no general agreement about which one is more appropriate. This letter proposes an E-Spiral algorithm for accurate photogrammetry that considers the camera sensor and the flight altitude to apply the overlapping necessary to guarantee the mission success. The algorithm uses an energy model to set different optimal speeds for straight segments of the path, reducing the energy consumption. We also propose an improvement for the energy model to predict the overall energy of the paths. We compare E-Spiral and E-BF algorithms in simulations over more than 3500 polygonal areas with different characteristics, such as vertices, irregularity, and size. Results showed that E-Spiral outperforms E-BF in all the cases, providing an effective energy saving even in the worst scenario with a percentage improvement of $10.37\%$ up to the best case with $\text{16.1}\%$ of improvement. Real flights performed with a quadrotor state the effectiveness of the E-Spiral over E-BF in two areas, presenting an improvement of $\text{9}\%$ in the time and $\text{7.7}\%$ in the energy. The improved energy model increases the time and the energy estimation precision of $\text{13.24}\%$ and $\text{13.41}\%$ , respectively.

Energy-Aware Spiral Coverage Path Planning for UAV Photogrammetric Applications

There are many protocols proposed for electronic voting, but only a few of them have prototypes implemented. Usually the prototypes are focused in the characteristics of the protocol and do not handle properly some real world issues, such as fault tolerance. This paper presents REVS, a robust electronic voting system designed for distributed and faulty environments, namely the Internet. The goal of REVS is to be an electronic voting system that accomplishes the desired characteristics of traditional voting systems, such as accuracy, democracy, privacy and verifiability. In addition, REVS deals with failures in real world scenarios, such as machine or communication failures, witch can lead to protocol interruptions. REVS robustness has consequences at three levels: (i) the voting process can be interrupted and recovered without weakening the voting protocol; (ii) it allows a certain degree of failures, with server replication; and (iii) none of the servers conducting the election, by its own or to a certain level of collusion, can corrupt the election outcome.

/pdf/revs-a-robust-electronic-voting-system-49dk21yw00.pdf

Revs – a robust electronic voting system

The increase in the number of SDN-based deployments in production networks is triggering the need to consider fault-tolerant designs of controller architectures. Commercial SDN controller solutions incorporate fault tolerance, but there has been little discussion in the SDN community on the design of such systems and the tradeoffs involved. To fill this gap, we present a by-construction design of a fault-tolerant controller, and materialize it by proposing and formalizing a practical architecture for small to medium-sized networks. A central component of our design is a replicated shared database that stores all network state. Contrary to the more common primary-backup approaches, the proposed design guarantees a smooth transition in case of failures and avoids the need of an additional coordination service. Our preliminary results show that the performance of our solution fulfils the demands of the target networks. We hope this work to be a first step in what we consider a necessary discussion on how to build robust SDNs.

/pdf/on-the-design-of-practical-fault-tolerant-sdn-controllers-3yvg9yf5bc.pdf

Paulo Ferreira

Papers

Survey on Coverage Path Planning with Unmanned Aerial Vehicles

SPL: An Access Control Language for Security Policies and Complex Constraints.

Energy-Aware Spiral Coverage Path Planning for UAV Photogrammetric Applications

Revs – a robust electronic voting system

On the Design of Practical Fault-Tolerant SDN Controllers