This thesis, studies automated methods to achieve web service advertisement and discovery, and presents efficient search and matching techniques based on OWL-S. In the proposed system, the service discovery and matchmaking is performed via a centralized peer-to-peer web service repository. The repository has the ability to run on a software cloud, which improves the availability and scalability of the service discovery. The service advertisement is done semi-automatically on the client side, with an automatic WSDL to OWL-S conversion, and manual service description annotation. An OWL-S based unified ontology -Suggested Upper Merged Ontology- is used during annotation, to enhance semantic matching abilities of the system. The service advertisement and availability are continuously monitored on the client side to improve the accuracy of the query results. User-agents generate query specification using the system ontology, to provide semantic unification between the client and the system during service discovery. Query matching is performed via complex Hilbert Spaces composed of conceptual planes and categorical similarities for each web service. User preferences following the service queries are monitored and used to improve the service match scores in the long run.

Peer-to-Peer (P2P) technology is a kind of decentralized framework which is applied to file sharing and video streaming in Internet predominantly. However, there are some problems, like free-riding, fairness, unexpected fluctuation, in P2P systems. Especially, without free riding controlling, many users stop contributing data and only want to receive data. To avoid these problems, a credit-based incentive mechanism using sneak, public-key cryptography and multi-source technique is proposed to make peers in system have no choice but to share data. In the proposed incentive mechanism, the concept of credit is employed. If a peer can contribute more bandwidth for sharing stream, it is arranged closer to video server, to get more credit in return, have less packet loss risk and receive better stream quality. Free-rider is a peer who denies contributing or contributes less resource than it registers to the system. In the proposed mechanism, free-riders are judged by the credits of each peer. In order to prevent illegal behaviors, the public-key cryptography is used for differentiating real and fake credit, also used for tracing credits. Experimental results show that when 90% peers are zero uploading peers, using the proposed mechanism can reduce 85% of zero uploading peers. When 90% peers are cheating peers, adopting the proposed mechanism can reduce 94% of cheating peers. System utility is usually about 100%. Maximum number of hops to video server is about five to six which is much smaller than without using the proposed mechanism, about 40 hops. The loads in managing system topology and delivering sub-streams are reduced. Besides, the resource of the system is used effectively.

Prior researches in P2P file sharing mostly focus on several topics such as the overlay topology, the content searching, the peer discovery, the sharing fairness, incentive mechanisms, except scheduling algorithms for peer-to-peer collaborative file distribution. The scheduling algorithm specifies how file pieces are distributed among peers. When a peer that has the rarest piece leaves, the other peers probably download the incomplete file in the network. Our algorithm is involved in the lifetime of peers in the P2P networks. We first use the distribution of peer¡¦s lifetime and the demand of each peer to decide which peers send which pieces that are rarities, and then also consider the distribution of peer¡¦s lifetime and the demand of each peer to decide which peers receive these pieces. Our goals are to maximize number of peers which have downloaded an entire file before it leaves, to increase the availability of different file pieces, and to minimize the transmission time of the latest completion. Lastly, we show the comparison of the performances of RPF, MDNF, Lifetime-based RPF, and Lifetime-based MDNF algorithms.

This work studies application acceleration for wireless and mobile data networks. The problem of accelerating application can be addressed along multiple dimensions. The first dimension is advanced network protocol design, i.e., optimizing underlying network protocols, particulary transport layer protocol and link layer protocol. Despite advanced network protocol design, in this work we observe that certain application behaviors can fundamentally limit the performance achievable when operating over wireless and mobile data networks. The performance difference is caused by the complex application behaviors of these non-FTP applications. Explicitly dealing with application behaviors can improve application performance for new environments. Along this overcoming application behavior dimension, we accelerate applications by studying specific types of applications including Client-server, Peer-to-peer and Location-based applications. In exploring along this dimension, we identify a set of application behaviors that significantly affect application performance. To accommodate these application behaviors, we firstly extract general design principles that can apply to any applications whenever possible. These design principles can also be integrated into new application designs. We also consider specific applications by applying these design principles and build prototypes to demonstrate the effectiveness of the solutions. In the context of application acceleration, even though all the challenges belong to the two aforementioned dimensions of advanced network protocol design and overcoming application behavior are addressed, application performance can still be limited by the underlying network capability, particularly physical bandwidth. In this work, we study the possibility of speeding up data delivery by eliminating traffic redundancy present in application traffics. Specifically, we first study the traffic redundancy along multiple dimensions using traces obtained from multiple real wireless network deployments. Based on the insights obtained from the analysis, we propose Wireless Memory (WM), a two-ended AP-client solution to effectively exploit traffic redundancy in wireless and mobile environments. Application acceleration can be achieved along two other dimensions: network provision ing and quality of service (QoS). Network provisioning allocates network resources such as physical bandwidth or wireless spectrum, while QoS provides different priority to different applications, users, or data flows. These two dimensions have their respective limitations in the context of application acceleration. In this work, we focus on the two dimensions of overcoming application behavior and Eliminating traffic redundancy to improve application performance. The contribution of this work is as follows. First, we study the problem of application acceleration for wireless and mobile data networks, and we characterize the dimensions along which to address the problem. Second, we identify that application behaviors can significantly affect application performance, and we propose a set of design principles to deal with the behaviors. We also build prototypes to conduct system research. Third, we consider traffic redundancy elimination and propose a wireless memory approach.

<p>This report concerns the implementation of a simulation framework to evaluate an emerging peer-to-peer network topology scheme using 8-point hypercircles, entitled HyperCircle. This topology was proposed in order to alleviate some of the drawbacks of current P2P systems evolving in an uncontrolled manner, such as scalability issues, network overload and long search times. The framework is supposed to be used to evaluate the advantages of this new topology. The framework has been built on top of an existing simulator software solution, the selection of which was an important part of the development. Weighing different variables such as scalability and API usability, the selection fell on OverSim, an open-source discreet-event simulator based on OMNET++.</p><p>After formalizing the protocol for easier implementation, as well as extending it for better performance, implementation followed using C++ with OverSim’s API and simulation library. Implemented as a module (alongside other stock modules providing their own protocols such as Chord and Kademlia), it can be used in OverSim to simulate a user-defined network using one of the simulation routine applications provided (or using a custom application written by the user). For the purposes of this thesis, the standard application KBRTestApp was used; an application sending test messages between randomly selected nodes, while adding and removing nodes at specific time intervals. The adding and removing of nodes can be configured with probability parameters.</p><p>Tentative testing shows that this implementation of the HyperCircle protocol has a certain performance gain over the OverSim implementations of the Chord and Kademlia protocols, measurable in the time it takes a message to get from sender to recipient. Further testing is outside the scope of this thesis.</p>

<p>In the environment of the 3:rd generation Internet based on peer-to-peer architecture, well-trusted methods must exist to establish a secure environment. One main issue is the possibility to verify that a node actually is who it claims to be (authentication). Establishment of authentication between nodes in a peer-to-peer environment where nodes are exchanging information directly with each other requires more planning than in a typical client-server environment where the authentication methods are server-based. The peer-to-peer applications described in this report use authentication methods based on central authorities as well as solutions without central authorities. </p><p>Lack of standards in the way peer-to-peer systems should communicate and apply security lead to a variety of “local” communication and security solutions. These local solutions make different applications incompatible with each other, meaning that a peer using one application will not be able to communicate and exchange information with other peers using some other application.</p>

The types of communication (central, semi-central, peripheral) Specification of the gnutella-protocol (PING, PONG, QUERY, QUERY-HIT, PUSH - packets) The graphical user interface Limewire and its class structure / Gemeinsamer Workshop von Universitaetsrechenzentrum und Professur Rechnernetze und verteilte Systeme der Fakultaet fuer Informatik der TU Chemnitz. Vergleich zentrale, semizentrale und dezentrale Kommunikation, Spezifikation eines P2P-Protokolls des Gnutella-Netzes (PING, PONG, QUERY, QUERY-HIT, PUSH - Pakete) Die graphische Oberflaeche Limewire und deren Struktur

Gemeinsamer Workshop von Universitaetsrechenzentrum und Professur Rechnernetze und verteilte Systeme der Fakultaet fuer Informatik der TU Chemnitz. Vortraege zu verschiedenen Themen der Entwicklung der Informatik und zu Technologien im Rechenzentrum einer Universitaet

Für Übertragung von Live-Videodaten an mehrere Empfänger gibt es als etablierte Technologien die Übertragung per Multicast an mehrere Empfänger sowie die Unicast-Übertragung an jeden Empfänger von einem Verteilpunkt aus. Nachteilig ist im ersten Fall, dass viele ISPs kein Multicast unterstützen, im zweiten Fall der hohe Bandbreitenbedarf am Verteilpunkt. Die Unterschiede in der verfügbaren Bandbreite von ISP-Zugängen (DSL, ISDN) und Campusnetzwerken (z.B. Studentennetzen) erfordern es, das Videomaterial in mehreren Qualitätsstufen anzubieten. Im Team wurde ein System entworfen und realisiert, das aus einer Quelle effizient verschiedene Qualitätsstufen des Videomaterials erzeugt ("Videoteil") und dieses mittels Peer-To-Peer-Technologie verteilt ("Netzwerkteil"). Diese Arbeit enthält den den Netzwerkteil.

An introduction to Chord Algorithm.