1,720,978 research outputs found
Study and analysis of innovative network protocols and architectures
Full text linkIn the last years, some new paradigms are emerging in the networking area as inspiring models for the definition of future communications networks. A key example is certainly the Content Centric Networking (CCN) protocol suite, namely a novel network architecture that aims to supersede the current TCP/IP stack in favor of a name based routing algorithm, also introducing in-network caching capabilities. On the other hand, much interest has been placed on Software Defined Networking (SDN), namely the set of protocols and architectures designed to make network devices more dynamic and programmable. Given this complex arena, the thesis focuses on the analysis of these innovative network protocols, with the aim of exploring possible design flaws and hence guaranteeing their proper operation when actually deployed in the network. Particular emphasis is given to the security of these protocols, for its essential role in every wide scale application. Some work has been done in this direction, but all these solutions are far to be considered fully investigated. In the CCN case, a closer investigation on problems related to possible DDoS attacks due to the stateful nature of the protocol, is presented along with a full-fledged proposal to support scalable PUSH application on top of CCN. Concerning SDN, instead, we present a tool for the verification of network policies in complex graphs containing dynamic network functions. In order to obtain significant results, we leverage different tools and methodologies: on the one hand, we assess simulation software as very useful tools for representing the most common use cases for the various technologies. On the other hand, we exploit more sophisticated formal methods to ensure a higher level of confidence for the obtained result
Push applications and dynamic content generation over content-centric networking
No full textContent-Centric Networking (CCN) represents an established candidate for the future Internet, proposing a routing architecture designed to elevate content to first class entity. Starting from the fact that the network usage has dramatically evolved towards content retrieval, CCN relies on an on-demand pull based mechanism to transfer data from the different sources to the heterogeneous consumers. This paradigm enhances the network in a number of ways, ranging from the newly introduced in-network caching capabilities to the benefits provided by the symmetric data routing adopted by CCN. In this renewed network scenario, we place our attention to those applications that do not perfectly fit the pull paradigm, stating that they need to be supported as well and proposing an effective way to achieve scalability on large scale push applications. We provide the following contributions: (i) we identify the functions that a data-centric architecture should support; (ii) propose and compare our solution with the state of the art framework designed for the specific problem of pushing data to content requesters; and (iii) evaluate their performance in terms of traffic generated and scalability achieved by simulating a real Internet Service Provider (ISP) topology and the realistic workload of a generic social network application
Development and characterization of novel PBI/SGO composites as possible proton exchange membranes filling the “conductivity gap”
Full text linkThe research for non-fluorinated polymeric electrolytes able to operate at temperatures of 80–120 °C, the so-called “conductivity gap”, is becoming central. Within this frame, the present work discusses the investigation of innovative self-assembling polybenzimidazole/sulfonated graphene oxide (PBI/SGO) composite membranes. A set of five samples, characterized by never-explored PBI-to-SGO mass ratios between 3:1 and 1:3, is studied through surface and cross-sectional SEM, XRD, ATR-FTIR spectroscopy, and TGA. The experimental outcomes reveal the reciprocal compatibility between PBI and SGO, whose main features appear to be evenly distributed within the composites. Water immersion tests demonstrate the excellent interplay between the membranes and the aqueous environment. EIS experiments, performed with the in-plane and through-plane configurations, disclose the improvement of the proton transfer ability (σ) in both directions. At 120 °C, PBI/SGO 1:2 achieves the highest in-plane σ of 0.113 S cm−1, while PBI/SGO 1:3 shows the best through-plane σ of 0.025 S cm−1. The preference toward planar proton migration is confirmed by the computation of the anisotropy factor, which is attenuated to ≈0.5 with the aid of temperature. Based on these findings, the composites with large SGO content seem to possess great potential as alternative non-fluorinated proton exchange membranes
Interest Flooding Attack Countermeasures Assessment on Content Centric Networking
Full text linkContent Centric Networking (CCN) has introduced new concepts and ideas in the next generation routing protocols research area, proposing an alternative approach to the well known and consolidated TCP/IP protocol suite. CCN envisions a network of smart caching devices that not only transport bits from one place to another but also support the network to provide end users with what they are really interested in: named data. However, while a large portion of the existing literature highlights the benefits of this new network paradigm, we focus on some specific security issues related to the opportunity of mounting distributed denial of service attacks, commonly known as Interest Flooding Attack (IFA). Our results confirm this possibility and assess the behavior of state of the art tools designed to mitigate this problem. We run different simulation campaigns in a real deployment scenario to support our evaluatio
PIT Overload Analysis in Content Centric Networks
Full text linkContent Centric Networking represents a paradigm shift in the evolution and definition of modern network protocols. Many research efforts have been made with the purpose of proving the feasibility and the scalability of this proposal. Our main contribution is to provide an analysis of the Pending Interest Table memory requirements in real deployment scenarios, especially considering the impact of distributed denial of service attacks. In fact, the state that the protocol maintains for each resource request makes the routers more prone to resources exhaustion issues than in traditional stateless solutions. Our results are derived by using a full custom simulator and considering the different node architectures that have been proposed as valid reference models. The main outcomes point out differentiated weaknesses in each architecture we investigated and underline the need for improvements in terms of security and scalabilit
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
A framework for user-friendly verification-oriented VNF modeling
No full textNetwork Function Virtualization (NFV) architectures are emerging to increase networks flexibility. However, this renewed scenario poses new challenges, because virtualized networks, need to be carefully verified before being actually deployed in production environments in order to preserve network coherency (e.g., absence of forwarding loops, preservation of security on network traffic, etc.). Nowadays, model checking tools, SAT solvers, and Theorem Provers are available for formal verification of such properties in virtualized networks. Unfortunately, most of those verification tools accept input descriptions written in specification languages that are difficult to use for people not experienced in formal methods. Also, in order to enable the use of formal verification tools in real scenarios, vendors of Virtual Network Functions (VNFs) should provide abstract mathematical models of their functions, coded in the specific input languages of the verification tools. This process is error-prone, time-consuming, and often outside the VNF developers' expertise. This paper presents a framework that we designed for automatically extracting verification models starting from a Java based representation of a given VNF. It comprises a Java library of classes to define VNFs in a more developer-friendly way, and a tool to translate VNF definitions into formal verification models of different verification tools
- …
