Aleksandra Kovacevic

PeerfactSim.KOM: A simulation framework for Peer-to-Peer systems

Since P2P systems have become popular in the late nineties, simulation of these systems has always been a preferable method of performance evaluation. Simulations facilitate the development and evaluation of new protocols and mechanisms, while enabling a comparison of existing solutions. In this paper, we present PeerfactSim.KOM, a discrete-event P2P simulator that is suitable for a wide range of varying scenarios in the area of P2P. It consists of a layered architecture, provides a broad selection of P2P protocols for the modeled layers, and eases the implementation of new components through its modular design. In addition, the simulator provides helpful tools to configure and evaluate a simulation scenario.

Modelling the Internet Delay Space Based on Geographical Locations

Existing approaches for modelling the Internet delay space predict end-to-end delays between two arbitrary hosts as static values. Further, they do not capture the characteristics caused by geographical constraints. Peer-to-peer (P2P) systems are, however, often very sensitive to the underlying delay characteristics of the Internet, since these characteristics directly influence system performance. This work proposes a model to predict lifelike delays between a given pair of end hosts. In addition to its low delay computation time, it has only linear memory costs which allows large scale P2P simulations to be performed. The model includes realistic delay jitter, subject to the geographical position of the sender and the receiver. Our analysis, using existing Internet measurement studies reveals that our approach seems to be an optimal tradeoff between a number of conflicting properties of existing approaches.

LifeSocial.KOM: A secure and P2P-based solution for online social networks

The phenomenon of online social networks reaches millions of users in the Internet nowadays. In these, users present themselves, their interests and their social links which they use to interact with other users. We present in this paper LifeSocial.KOM, a p2p-based platform for secure online social networks which provides the functionality of common online social networks in a totally distributed and secure manner. It is plugin-based, thus extendible in its functionality, providing secure communication and access-controlled storage as well as monitored quality of service, addressing the needs of both, users and system providers. The platform operates solely on the resources of the users, eliminating the concentration of crucial operational costs for one provider. In a testbed evaluation, we show the feasibility of the approach and point out the potential of the p2p paradigm in the field of online social networks.

Globase.KOM - A P2P Overlay for Fully Retrievable Location-based Search

Location based services are becoming increasingly popular as devices that determine geographical position become more available to end users. The main problem of existing solutions to location-based search is keeping information updated requires centralized maintenance at specific times. Therefore, retrieved results do not include all objects that exist in reality. A peer-to-peer (P2P) 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 P2P overlay that enables fully retrievable location-based overlay operations which proved to be highly efficient and logarithmically scalable.

Practical security in p2p-based social networks

The peer-to-peer paradigm is used in more and more advanced applications. One of the next areas that promise a success for the p2p paradigm lies in the upcoming trend of social networks. However, several security issues have to be solved in p2p-based social network platforms. We present in this paper a practical solution that establishes a trust infrastructure, enables authenticated and secure communication between users in the social network and provides personalized, fine grained data access control. We implemented our solution in a p2p based platform for social networks and show that the solution is practical and lightweight both in time consumption and traffic overhead.

A Distributed Platform for Multimedia Communities

Online community platforms and multimedia content delivery are merging in recent years. Current platforms like Facebook and YouTube are client-server based which result in high administration costs for the provider. In contrast to that peer-to-peer systems offer scalability and low costs, but are limited in their functionality.In this paper we present a framework for peer-to-peer based multimedia online communities. We identified the key challenges for this new application of the peer-to-peer paradigm and built a plugin based, easily extendible and multi-functional framework. Further, we identified distributed linked lists as valuable data structure to implement the user profiles, friend lists, groups, photo albums and more. Our framework aims at providing the functionality of common online community platforms combined with the multimedia delivery capabilities of modern peer-to-peer systems, e.g. direct multimedia delivery and access to a distributed multimedia pool.

LifeSocial.KOM: A P2P-Based Platform for Secure Online Social Networks

Online social networks with millions of users are very popular nowadays. They provide a platform for the users to present themselves and to interact with each other. In this paper, we present a totally distributed platform for social online networks based on the p2p paradigm, called LifeSocial.KOM. It provides the same functionality as common online social networks, while distributing the operational load on all participating nodes. LifeSocial.KOM is plugin-based and extendible, provides secure communication and user-based data access control and integrates a monitoring component which allows the users and operators to observe the quality of the distributed system.

Enabling resilient P2P video streaming: survey and analysis

Peer-to-Peer (P2P) techniques for multimedia streaming have been shown to be a good enhancement to the traditional client/server methods when trying to reduce costs and increase robustness. Due to the fact that P2P systems are highly dynamic, the main challenge that has to be addressed remains supporting the general resilience of the system. Various challenges arise when building a resilient P2P streaming system, such as network failures and system dynamics. In this paper, we first classify the different challenges that face P2P streaming and then present and analyze the possible countermeasures. We classify resilience mechanisms as either core mechanisms, which are part of the system, or as cross-layer mechanisms that use information from different communication layers, which might inflict additional costs. We analyze and present resilience mechanisms from an engineering point of view, such that a system engineer can use our analysis as a guide to build a resilient P2P streaming system with different mechanisms and for various application scenarios.

Monitoring and management of structured peer-to-peer systems

The peer-to-peer paradigm shows the potential to provide the same functionality and quality like client/server based systems, but with much lower costs. In order to control the quality of peer-to-peer systems, monitoring and management mechanisms need to be applied. Both tasks are challenging in large-scale networks with autonomous, unreliable nodes. In this paper we present a monitoring and management framework for structured peer-to-peer systems. It captures the live status of a peer-to-peer network in an exhaustive statistical representation. Using principles of autonomic computing, a preset system state is approached through automated system re-configuration in the case that a quality deviation is detected. Evaluation shows that the monitoring is very precise and lightweight and that preset quality goals are reached and kept automatically.

Load balancing for multimedia streaming in heterogeneous peer-to-peer systems

Multimedia streaming of mostly user generated content is an ongoing trend, not only since the upcoming of Last.fm and YouTube. A distributed decentralized multimedia streaming architecture can spread the (traffic) costs to the user nodes, but requires to provide for load balancing and consider the heterogeneity of the participating nodes. We propose a DHT-based information gathering and analyzing architecture which controls the streaming request assignment in the system and thoroughly evaluate it in comparison to a distributed stateless strategy. We evaluated the impact of the key parameters in the allocation function which considers the capabilities of the nodes and their contribution to the system. Identifying the quality-bandwidth tradeoffs of the information gathering system, we show that with our proposed system a 53% better load balancing can be reached and the efficiency of the system is significantly improved.