[Show abstract][Hide abstract] ABSTRACT: The peer-to-peer paradigm gained more and more impact in the last years. The reason for P2P arising now is related to the continuous development of device capabilities in the last years, like CPU power, storage space and bandwidth. However, the demand for services and resources is permanently increasing, although the peers have a variety of other resources themselves. In this paper we present the idea of a P2P system acting as a service provider using the resources of participating peers and stating guarantees on the quality of the service it provides. In order to fulfill these service level agreements, the peers confederate to a distributed supervisor of peer resources (DISPRO), monitoring the network, predicting trends on resource availabilities and deciding on resource allocation strategies. This paper discusses the challenges and a solution draft of the concept of DISPRO.
[Show abstract][Hide abstract] ABSTRACT: Reliable communication systems are one of the key success factors for a successful first response mission. Current crisis response communication systems suffer from damaged or destroyed infrastructure or are just overstressed in the case of a large scale disaster. We provide an outline for a distributed communication approach, which fulfills the requirements of first responders. It is based on a layered network topology and current technology used in research projects or already established products. In addition, we propose a testing framework for the evaluation of a crisis response communication system.
[Show abstract][Hide abstract] ABSTRACT: This demo paper presents an prototype implementation of a decentralized and distributed approach for spatial queries. The
main focus is the location-based search for all the objects or information in the particular geographical area.
Database Systems for Advanced Applications, 14th International Conference, DASFAA 2009, Brisbane, Australia, April 21-23, 2009. Proceedings; 01/2009
[Show abstract][Hide abstract] ABSTRACT: Multimedia creation and consumption is highly intensive and makes up the majority of Internet traffic nowadays. End-users are able to share their digital content with each other and to build communities based on interests, which often differ drastically according to location. Distributing these media using a central server can be quite expensive for a content provider. Distributed (peer-to-peer like) systems share costs evenly among participants. Thus, distributed multimedia systems will be more important in the future. The global distribution of end-users aggravates high-quality delivery of multimedia content. In this paper, we argue that geographical location-awareness greatly helps distributed multimedia communication. It increases the quality of multimedia content delivery and at the same time satisfies the growing need for more personalized, location-based services. In this paper, as a proof of concept, we introduce an overlay structure for distributed multimedia systems (and similar systems), which is location-aware and uses the locations of its nodes to optimize node-to-node communication for performance and delay. At the same time, the system enables location-based services.
Proceedings of the IEEE 02/2008; · 5.47 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Information Lifecycle Management (ILM) speichert Dateien gemäß ihres Wertes. Somit ist die Wertzuweisung von Dateien eine der Hauptaufgaben in ILM. In diesem Papier betrachten wir wie der Wert einer Datei bestimmt werden kann. Während die bekannten Methoden einen Wert als Dezimalzahl ermitteln, präsentieren wir eine Methode, die den Wert einer Datei als die "Wahrscheinlichkeit zukünftiger Zugriffe" ermittelt. Die Anwendbarkeit dieser Methode stellen wir mittels Simulation dar. Dabei vergleichen wir die neue Methode mit einer als Benchmark dienenden optimalen Methode, die allerdings nur unter Laborbedingungen funktioniert.
[Show abstract][Hide abstract] ABSTRACT: Peer-to-peer and mobile networks gained significant attention of both research community and industry. Applying the peer-to-peer paradigm in mobile networks lead to several problems regarding the bandwidth demand of peer-to-peer networks. Time-critical messages are delayed and delivered unacceptably slow. In addition to this, scarce bandwidth is wasted on messages of less priority. Therefore, the focus of this paper is on bandwidth management issues at the overlay layer and how they can be solved. We present HiPNOS.KOM, a priority based scheduling and active queue management system. It guarantees better QoS for higher prioritized messages in upper network layers of peerto- peer systems. Evaluation using the peer-to-peer simulator PeerfactSim.KOM shows that HiPNOS.KOM brings significant improvement in Kademlia in comparison to FIFO and Drop-Tail, strategies that are used nowadays on each peer. User initiated lookups have in Kademlia 24% smaller operation duration when using HiPNOS.KOM.
[Show abstract][Hide abstract] ABSTRACT: Location based services are becoming increasingly popular as devices that determine the geographical position got more available to the end users. The problem of existing solutions to location-based search, e.g. in car navigation systems, is keeping information updated because of centralized main- tenance at specific times. Therefore, retrieved results do not include all objects that exist in reality. A peer-to-peer approach can easily overcome this issue as peers are responsible for the information users are searching for. Unfortunately, current state- of-the-art overlays cannot fulfill the requirements for efficient and fully retrievable location-based search. In this paper we present Globase.KOM, a hierarchical tree-based peer-to-peer overlay that enables fully retrievable area search, lookup, and finding the geographically closest node. Simulation results prove that the overlay operations of Globase.KOM are highly efficient, fully retrievable, and logarithmically scalable. Protocol overhead and load of the peers in the overlay have been evaluated as well. I. I NTRODUCTION Location based services are becoming increasingly popular - navigation systems, tracking and logistic systems, mobile billing (e.g. toll) or mobile advertising are just some of them. Search for objects/information located in some area are part of many search engines or navigation systems. Additionally, devices that determine the geographical position (e.g. a GPS receiver) are already integrated in many Pocket PCs and integration into standard laptops and other end-systems can be expected soon. This location information enables for more convenient, highly personalized services for users, like for example, finding the closest restaurant. In existing solutions for location-based search the search results are often incomplete or outdated. Information in a peer-to-peer-based solution could be kept updated much better than in centrally managed systems even with the fast growth of the system. The cases of passing by a gasoline station while our navigation system shows that the closest gasoline station is 5 km away, or navigating through a blocked road can be avoided. Further, the system could be operated with low costs, because of the natural scalability and administration-free character of peer-to-peer systems. In spite of the fact that the peer-to-peer research community is very active since the last seven years, current state-of-the- art overlays cannot fulfill the requirements for efficient and fully retrievable location-based search. In this paper we present Globase.KOM, a hierarchical tree-based peer-to-peer overlay that enables fully retrievable area search, lookup, and finding the geographically closest node. This paper is organized as follows. In the Section II we discuss the goals, requirements, and assumption for our solu- tion. The design of Globase.KOM - overlay structure, overlay operations, and failure recovery, is presented in Section III. Evaluation in Section IV shows the performance of overlay operations as well as protocol overhead, load balance, and effects of overlay parameters on the performance. The related work is surveyed in Section V. The paper is concluded in Section VI.
Seventh IEEE International Conference on Peer-to-Peer Computing (P2P 2007), September 2-5, 2007, Galway, Ireland; 10/2007
[Show abstract][Hide abstract] ABSTRACT: Structured overlay networks for Peer-to-Peer systems (e.g. based on Distributed Hash Tables) use proactive mechanisms to provide
efficient indexing functionality for advertised resources. The majority of their occurrences in proposed systems (e.g. Chord,
Pastry) provide upper bounds (logarithmic complexity with respect to the size of the graph representing the network) on the
communication cost in worst case scenarios and their performance is superior compared to unstructured alternatives. However,
in particular (empirically observed) scenarios where the popularity of the advertised resources follows a distribution considerably
different from the uniform distribution, structured P2P networks may perform inferiorly compared to well designed unstructured
P2P networks that exploit effectively the resource popularity distribution. In order to address this issue, a very simple
caching mechanism is suggested in this paper that preserves the theoretical superiority of structured overlay networks regardless
of the popularity of the advertised resources. Moreover, the churn effect observed in Peer-to-Peer systems is considered.
The proposed mechanism is evaluated using simulation experimesnts.
[Show abstract][Hide abstract] ABSTRACT: Today, Peer-to-Peer applications are predominant on the internet when considered in terms of its traffic consumption. However
apart from Skype, their commercial success is still very limited. This is due to the difficulties faced when trying to implement
crucial functionality such as accounting and charging without violating the Peer-to-Peer paradigm. A fully decentralized accounting
scheme based on tokens was presented by the authors last year. In this paper we analyse the interactions between token-based
accounting and charging in order to enable peers to charge for their services. We present three different charging schemes
using tokens as (1) pure receipts, as (2) Micropayment, and as (3) bill of exchange. These schemes are evaluated based on
the provided security and the overhead traffic introduced into a Peer-to-Peer system.
[Show abstract][Hide abstract] ABSTRACT: The intrinsic properties of the employed graphs in designing peer-to-peer overlay networks are crucial for the performance of the deployed peer-to-peer systems. Several structured topologies have been proposed based on meshes, enhanced rings, redundant tree structures, etc. Among them, de Bruijn graphs are promising alternatives since they provide some crucial asymptotically optimal characteristics. In this paper, we discuss the necessary algorithms and protocol messages to develop efficiently the employed routing procedure of Omicron, which is a hybrid overlay network based on de Bruijn graphs enriched with clustering and role specialization mechanisms. Enhancements of the original de Bruijn structure are advised to cope with the intrinsic issue of uneven distribution of the routing workload. The developed system is evaluated and compared with Chord, which is used as the reference point. The superiority of de Bruijn based overlay networks with respect to scalability is quantitatively demonstrated using simulation experiments. Further, the ability of the two systems to exploit the underlying network is investigated