Stuttgart, Univ., Studienarbeit, 2007.

In this paper, we investigate the topology convergence problem for the gossip-based Gradient overlay network. In an overlay network where each node has a local utility value, a Gradient overlay network is characterized by the properties that each node has a set of neighbors containing higher utility values, such that paths of increasing utilities emerge in the network topology. The Gradient overlay network is built using gossiping and a preference function that samples from nodes using a uniform random peer sampling service. We analyze it using tools from matrix analysis, and we prove both the necessary and sufficient conditions for convergence to a complete gradient structure, as well as estimating the convergence time. Finally, we show in simulations the potential of the Gradient overlay, by building a more efficient live-streaming peer-to-peer (P2P) system than one built using uniform random peer sampling. / <p>© 2011 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. QC 20111124</p>

The Internet is a common technology nowadays in our daily life. More and more people think it will soon replace traditional mass media and become the new age public forum. However, the cyberspace is not as open, free, and democratic as we may imagine. Actually more and more regulations and rules are imposed on it. But deviating behaviors such as conflicts, crimes, and violence did not decrease with all the regulations and rules. And the hierarchy of power and class did not disappear from the cyberspace as the internet utopians described. The researcher investigated one of the biggest and most popular virtual community in Taiwan, Gassiping Board in PTT Bulletin Board System, in particular regulation and power aspects, and tried to find out what is behind the regulations and how the collective behaviors of the users collide with the power of the administrators and the order of the board. Do they reflect any social value or internet culture? And what is the connection with the real world? With the idea of regulation in Lawrence Lessig¡¦s book Code v2 and the concept of cyberpower, the researcher analysed the important changes and conflicts occurred on Gassiping Board. Gassiping Board can be seen as a free speech market by Lessig¡¦s concept, and the rules serving as laws, which give power to the administrators, along with the internet norms, regulate the behaviour of the users. By the code, the administrators can execute the rules. However, the common users have their own power given by the design of the code to rival the administrators, and they can even change the rules, the norms, and the free speech market of Gassiping Board. Also, some changing effects come from outside the virtual community, namely from the real world. Although the administrators have superior power of technology, most of the time they are low in authority. It is hard for them to regulate all the users under the anti-control culture in the cyberspace. The users of Gassiping Board will gather all their powers when it is necessary, and will even destroy the order and overthrow the power of the administrators. However, this phenomenon indicates self-centredness and lack of respect to others, no matter if it is led by the common users or the administrators. Even though the internet is a modern technology product, in practice modern values such as the quality of democracy, law and order can not work with the internet users in making the virtual community a public sphere with both freedom and order.

Zugl.: Kaiserslautern, Techn. University, Diss., 2008.

Zugl.: Kaiserslautern, Techn. Univ., Diss., 2008

Zone Routing Protocol (ZRP) is a typical hybrid routing protocol used in Mobile Ad Hoc Networks (MANETs). Hybrid routing protocols are especially suitable for dynamic environments because they combine the best features of proactive and reactive routing protocols. The Gossip-based Zone Routing Protocol (GZRP) uses a gossip scheme, in which the node forwards a packet to some nodes instead of all nodes to further reduce the control overhead. However, GZRP does not perform well when the network includes articulation points since packets will be lost if an articulation node happens not to forward the packet or nodes happen not to forward packets to the articulation point. To raise the packet delivery ratio, the gossip probability of articulation points must be set to 1 and the packets to be forwarded must be sent to the articulation points in peripheral nodes. Accordingly, how to identify articulation nodes in the network becomes a critical issue. This paper proposes an effective scheme, called articulation point detection (APD), to find the articulation points. Simulation results show that the proposed APD-GZRP (GZRP with articulation point detection) can improve the packet delivery ratio and reduce both the control overhead and power consumption.

Broadcasting is a communication model for a node to emit the packets via wireless channels to its neighbor nodes. In mobile ad hoc networks (MANETs), it is commonly implemented through flooding to find routes, send alarm signals and page a particular host. Conventionally, ad hoc routing protocols, such as AODV, use blind flooding extensively for on-demand route discovery, which could result in a high number of redundant retransmissions, leading to serious contention and collisions referred to as the broadcast storm problem. A gossip-based approach, in which each node forwards a message with some probability, has been proposed in past years to alleviate this problem. The approach combines gossiping with AODV (denoted as AODV+G) and exhibits a significant performance improvement in simulations. In this paper, we make a mathematical inference from observing the behavior of the gossip-based approach, and improve the gossip-based approach by employing the remaining energy of nodes in the gossip mechanism (denoted as AODV+GE) to extend the lifetime of the entire network and improve the packet delivery ratio. Through mathematical inference and simulations we show that AODV+GE outperforms AODV+G in terms of the lifetime of the whole network, average node energy consumption, and packet delivery ratio.

Konstanz, Univ., Diplomarb., 2005.

abstract: Wireless sensor networks (WSN) and the communication and the security therein have been gaining further prominence in the tech-industry recently, with the emergence of the so called Internet of Things (IoT). The steps from acquiring data and making a reactive decision base on the acquired sensor measurements are complex and requires careful execution of several steps. In many of these steps there are still technological gaps to fill that are due to the fact that several primitives that are desirable in a sensor network environment are bolt on the networks as application layer functionalities, rather than built in them. For several important functionalities that are at the core of IoT architectures we have developed a solution that is analyzed and discussed in the following chapters. The chain of steps from the acquisition of sensor samples until these samples reach a control center or the cloud where the data analytics are performed, starts with the acquisition of the sensor measurements at the correct time and, importantly, synchronously among all sensors deployed. This synchronization has to be network wide, including both the wired core network as well as the wireless edge devices. This thesis studies a decentralized and lightweight solution to synchronize and schedule IoT devices over wireless and wired networks adaptively, with very simple local signaling. Furthermore, measurement results have to be transported and aggregated over the same interface, requiring clever coordination among all nodes, as network resources are shared, keeping scalability and fail-safe operation in mind. Furthermore ensuring the integrity of measurements is a complicated task. On the one hand Cryptography can shield the network from outside attackers and therefore is the first step to take, but due to the volume of sensors must rely on an automated key distribution mechanism. On the other hand cryptography does not protect against exposed keys or inside attackers. One however can exploit statistical properties to detect and identify nodes that send false information and exclude these attacker nodes from the network to avoid data manipulation. Furthermore, if data is supplied by a third party, one can apply automated trust metric for each individual data source to define which data to accept and consider for mentioned statistical tests in the first place. Monitoring the cyber and physical activities of an IoT infrastructure in concert is another topic that is investigated in this thesis. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2017

Video delivery over the Internet is becoming increasingly popular and comes in many flavors, such as Live Streaming and Video-on-Demand. In the recent years, many peer to peer solutions for Live Streaming and VoD have been proposed as opposed to the centralized solutions that are not scalable due to the high bandwidth requirements. In all existing solutions, Live Streaming and VoD have traditionally and artificially been considered as separate technical problems. We propose an integrated Live Streaming with VoD system that offers the potential for users to watch live TV with short delays. In Live Streaming, peers are interested in the content that is being generated live by the streaming source, unlike VoD in which peers are interested in the content that has been generated from the beginning of the streaming. In this manner, Live nodes can contribute to VoD nodes and send them the pieces they have downloaded since their joining time. In this work, we demonstrate that our system, called Live-VoD, brings out the possibility of having both types of nodes in one system, each being served based on their interest. We propose a P2P Live-VoD protocol for overlay construction based on peer’s upload bandwidth that is built on top of the Gradient topology and an innovative algorithm based on the number of pieces peers can contribute to each other. We also propose an innovative stochastic algorithm for data dissemination based on the rareness of the piece and the requesting node’s download position. Our experiments show that Live-VoD is decentralized, scalable and self-organizing. We also show that even when most of the nodes in the system are VoDs, all VoD nodes regardless of their joining time, manage to download the whole movie with no assistance from the streaming source.