Replication in bandwidth-symmetric BitTorrent networks

The popular and well-known BitTorrent peer-to-peer protocol offers fast file distribution in a highly scalable way. Several studies have investigated the properties of this protocol, mostly focusing on heterogeneous end-user environments such as the Internet, with asymmetric connections. In this paper however, we focus on the usage of the BitTorrent protocol in homogeneous local environments with symmetric bandwidth properties. Compared with a traditional client-server setup, the use of BitTorrent in such settings can offer huge benefits in performance and scalability, allowing bandwidth sharing and high speed file distribution. We aim to improve the performance of such networks with a novel mechanism for replication using so-called replicators, which replicate a subset of the files in the system. A mathematical model of the resulting Replicated BitTorrent is presented and validated by emulation. Furthermore, we present simulation results that provide insight in the performance of Replicated BitTorrent networks with dynamic peer arrivals and departures. The results show that Replicated BitTorrent significantly improves download times in local bandwidth-symmetric BitTorrent networks

BlockTorrent: A Privacy-Preserving Data Availability Protocol for Multiple Stakeholder Scenarios

As industries across the globe continue to digitize their processes, the need for a mechanism to share private data between multiple stakeholders is becoming increasingly apparent. However, sharing data poses challenges around privacy and accessibility, particularly in disputes between stakeholders with a shared interest, such as a supply chain. Auditors currently rely on stakeholders’ compliance in order to verify data. Malicious parties may falsify the data before passing it on to the auditor. Using supply chains as a case study we present BlockTorrent, a protocol to address these challenges and help facilitate data sharing between supply chain participants and named after the integration of Blockchain technology and the BitTorrent protocol. BlockTorrent allows participants to securely share their data in near real-time with other participants without the risk of information leakage or allowing data falsification, whilst guaranteeing data availability for auditors. This is achieved using a novel combination of distributed storage and on-chain secret sharing. This thesis provides an implementation and evaluation of BlockTorrent, highlighting its performance and a security discussion, specifically that a system like BlockTorrent can reach large transaction throughput as high as 500 tps and be viable in a real world environment. Lastly, the thesis provides a discussion on the privacy challenges that were considered when designing BlockTorrent

Semantic search and composition in unstructured peer-to-peer networks

This dissertation focuses on several research questions in the area of semantic search and composition in unstructured peer-to-peer (P2P) networks. Going beyond the state of the art, the proposed semantic-based search strategy S2P2P offers a novel path-suggestion based query routing mechanism, providing a reasonable tradeoff between search performance and network traffic overhead. In addition, the first semantic-based data replication scheme DSDR is proposed. It enables peers to use semantic information to select replica numbers and target peers to address predicted future demands. With DSDR, k-random search can achieve better precision and recall than it can with a near-optimal non-semantic replication strategy. Further, this thesis introduces a functional automatic semantic service composition method, SPSC. Distinctively, it enables peers to jointly compose complex workflows with high cumulative recall but low network traffic overhead, using heuristic-based bidirectional haining and service memorization mechanisms. Its query branching method helps to handle dead-ends in a pruned search space. SPSC is proved to be sound and a lower bound of is completeness is given. Finally, this thesis presents iRep3D for semantic-index based 3D scene selection in P2P search. Its efficient retrieval scales to answer hybrid queries involving conceptual, functional and geometric aspects. iRep3D outperforms previous representative efforts in terms of search precision and efficiency.Diese Dissertation bearbeitet Forschungsfragen zur semantischen Suche und Komposition in unstrukturierten Peer-to-Peer Netzen(P2P). Die semantische Suchstrategie S2P2P verwendet eine neuartige Methode zur Anfrageweiterleitung basierend auf Pfadvorschlägen, welche den Stand der Wissenschaft übertrifft. Sie bietet angemessene Balance zwischen Suchleistung und Kommunikationsbelastung im Netzwerk. Außerdem wird das erste semantische System zur Datenreplikation genannt DSDR vorgestellt, welche semantische Informationen berücksichtigt vorhergesagten zukünftigen Bedarf optimal im P2P zu decken. Hierdurch erzielt k-random-Suche bessere Präzision und Ausbeute als mit nahezu optimaler nicht-semantischer Replikation. SPSC, ein automatisches Verfahren zur funktional korrekten Komposition semantischer Dienste, ermöglicht es Peers, gemeinsam komplexe Ablaufpläne zu komponieren. Mechanismen zur heuristischen bidirektionalen Verkettung und Rückstellung von Diensten ermöglichen hohe Ausbeute bei geringer Belastung des Netzes. Eine Methode zur Anfrageverzweigung vermeidet das Feststecken in Sackgassen im beschnittenen Suchraum. Beweise zur Korrektheit und unteren Schranke der Vollständigkeit von SPSC sind gegeben. iRep3D ist ein neuer semantischer Selektionsmechanismus für 3D-Modelle in P2P. iRep3D beantwortet effizient hybride Anfragen unter Berücksichtigung konzeptioneller, funktionaler und geometrischer Aspekte. Der Ansatz übertrifft vorherige Arbeiten bezüglich Präzision und Effizienz

Replication in bandwidth-symmetric BitTorrent networks

The popular and well-known BitTorrent peer-to-peer protocol offers fast file distribution in a highly scalable way. Several studies have investigated the properties of this protocol, mostly focusing on heterogeneous end-user environments such as the Internet, with asymmetric connections. In this paper however, we focus on the usage of the BitTorrent protocol in homogeneous local environments with symmetric bandwidth properties. Compared with a traditional client-server setup, the use of BitTorrent in such settings can offer huge benefits in performance and scalability, allowing bandwidth sharing and high speed file distribution. We aim to improve the performance of such networks with a novel mechanism for replication using so-called replicators, which replicate a subset of the files in the system. A mathematical model of the resulting Replicated BitTorrent is presented and validated by emulation. Furthermore, we present simulation results that provide insight in the performance of Replicated BitTorrent networks with dynamic peer arrivals and departures. The results show that Replicated BitTorrent significantly improves download times in local bandwidth-symmetric BitTorrent networks