Dokument: The Impact of Resource Sharing on Coexisting P2P Overlays and Stacked Overlay Modules
| Titel: | The Impact of Resource Sharing on Coexisting P2P Overlays and Stacked Overlay Modules | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=44295 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20171204-115649-7 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Amft, Tobias [Autor] | |||||||
| Dateien: |
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| Beitragende: | Jun.-Prof. Dr. Graffi, Kalman [Gutachter] Prof. Dr. Mauve, Martin [Gutachter] | |||||||
| Stichwörter: | P2P, coexistence, overlay, modules, peer | |||||||
| Dokumententyp (erweitert): | Dissertation | |||||||
| Dewey Dezimal-Klassifikation: | 000 Informatik, Informationswissenschaft, allgemeine Werke 000 Informatik, Informationswissenschaft, allgemeine Werke » 004 Datenverarbeitung; Informatik | |||||||
| Beschreibung: | In contrast to traditional client-server approaches, peer-to-peer (P2P) systems do not follow a strict centralized infrastructure paradigm.
Instead, the functionality of one specific P2P system is distributed over all its participants fully or partially, depending on its purpose. Thus, the most outstanding characteristic of P2P systems is that they organize their own infrastructure and thus remain scalable even if they grow or shrink. Peer-to-peer overlays which can be part or base of a complex P2P system introduce further logical layers on top of existing layers and extend their underlaying networks with own routing tables and forwarding strategies. The parallel execution and combination of multiple overlays with different and contrasting functionalities has been rarely considered in preceding research, although the combination and conjunction of specialized overlays seem to be a promising approach to reduce maintenance, implementation and execution costs of all overlays running on one single peer. In order to motivate our research on P2P networks, we review political events which took place around 2010 and 2011 in the Middle East and Northern African region. We review modern techniques used by governments and oppressive regimes to monitor and censor Internet traffic and we discuss possible countermeasures against their attacks. Considering the uprisings during the Arab Spring and the related Internet shutdown events as they happened in Egypt and Libya in 2011, we find that distributed applications are highly demanded niche products among the increasing amount of services offered on the Internet. In this thesis, we focus on the optimization of coexisting P2P overlays and applications operated in parallel on one peer. We identify basic requirements and characteristics of P2P overlays and applications and identify patterns which are frequently repeated, with the goal to avoid duplicate implementation and operating costs and to describe a methodology to create new overlays efficiently. As result, we present a novel approach to build coexisting overlays, named overlay stack, which is the idea to combine different overlay parts in a way that a desired behavior is obtained and second, that the implementation of duplicate modules and functionalities is avoided so that unnecessary expenses are kept at a minimum. Following our goal, we focus on a contrasting set of overlays which differ in their requirements and functionalities so that core functionalities of P2P overlays and applications can be found. We divide the considered overlays into location-centric and social-centric approaches with restricted or free possibilities to communicate. With the implementations and evaluations of the proposed overlays algorithms in the four categories we show that a distributed hash table (DHT) or another indexing overlay constitutes a suitable basis for a diverse set of P2P applications. Moreover, we show that a DHT as basis is suitable to realize a contrasting range of P2P applications on top and identify one possible way to organize coexisting overlays on a single peer. The main benefit of a common DHT as basis for multiple overlays is that maintenance costs and vital update mechanisms are only spent once. By applying new applications on top of the common DHT or other existing overlays, our overlay stack can be extended vertically with new functionalities. Pursuing or goal to find core P2P functions, we present a new approach to enhance existing DHTs with social-relationship graphs according to Dunbar's Social Brain Hypothesis. Our approach enables trusted, friendship-based routing in structured P2P networks on the one hand and replication on trusted nodes with high data availability ratios on the other hand. We show that data in distributed online social networks can be kept available if few friends of a node are used as replication nodes only. Applications using the proposed social DHT benefit from the existing routing table and are able to use already known contacts for bootstrapping. In the field of location-aware services, we identify two classes of overlays and compare them in in a simulations-driven evaluation. Doing this, we show how mapping-based overlays can be realized on top of existing DHTs in the way that both, the location-based application and the underlaying DHT are decoupled so that they can be exchanged at any time. In the fourth category of investigated overlays, we show that during isolation, the ring structure in Chord overlays breaks up so that multiple separated communication islands are formed which are not able to re-structure without external help. To overcome this issue, we present our Ring Reunion merging algorithm which in case of isolation events is activated to re-organize corrupt overlay structures while keeping additional message overhead low. Applying different P2P applications on a common DHT, we notice that one DHT defines a good core set of functionalities for different P2P applications, but is not sufficient to serve all demands of all possible applications, especially in cases in which more specialized routing mechanisms are required. To further reduce implementation and operating costs in DHT and other routing overlays, we search for a more general core set of overlay functionality and find out that P2P overlays mainly consist of three overlay modules which serve one specific purpose in the overlay. Routing tables are passive modules which give access to contact information to other modules. Routing algorithms are modules which implement forwarding rules and therefore shape the behavior of the overlay. Additional update mechanisms, like join operations or periodic keep-alive messages, are used to fill and update the routing table of an overlay. Introducing a common routing table, which serves other overlay modules, we are able to reduce further costs caused by duplicate modules and we allow to extend our overlay stack horizontally with new overlay functionalities. In conclusion, we propose the overlay stack, a novel methodology to build coexisting overlays. We show that P2P applications in the overlay stack can be built on top of existing structures, and we show that new overlay functionalities can be added in form of specialized overlay modules on top of a common routing table. In addition, we show in our evaluation that the use of a shared routing table increases the robustness of all participating overlays while operating costs and implementation costs of the overlays are reduced. We further show that an overlay stack allows to switch on and off new routing functionalities during runtime, since the common routing table supports bootstrapping new overlays without the need of full join procedures. | |||||||
| Lizenz: |  Urheberrechtsschutz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät » WE Informatik Mathematisch- Naturwissenschaftliche Fakultät » WE Informatik » Rechnernetze | |||||||
| Dokument erstellt am: | 04.12.2017 | |||||||
| Dateien geändert am: | 04.12.2017 | |||||||
| Promotionsantrag am: | 11.09.2017 | |||||||
| Datum der Promotion: | 23.10.2017 |
