Dominik Stingl

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.

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.

Simonstrator: simulation and prototyping platform for distributed mobile applications

The increasing market penetration of mobile devices, such as smartphones and tablets, poses additional challenges on the design of distributed systems. Due to the heterogeneous environment consisting of both, mobile and fixed devices, a multitude of effects on different scales need to be considered. Microscopic effects, such as an individual users interaction with the device, as well as macroscopic effects, such as scalability with the number of users have an impact on the systems performance. The combined evaluation of micro- and macroscopic effects requires both, simulations and prototypical deployments. Furthermore, insights obtained through prototypes during user studies can lead to refined protocols and algorithms, thereby contributing to the overall design process. To enable parallel assessment of micro- and macroscopic effects, we propose the Simonstrator platform, consisting of a lightweight framework for the development and instrumentation of distributed systems as well as runtime environments for (i) the interaction with common simulators, (ii) the deployment on testbeds, and (iii) Android devices. The platform is specifically targeted towards distributed systems for heterogeneous scenarios, considering mobile and fixed networks. We show sample simulations and prototypical deployments of two exemplary use cases: a live video streaming system and a middleware for augmented reality games, highlighting different evaluation goals and environments supported by the proposed Simonstrator platform.

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.

Towards a P2P Cloud: Reliable Resource Reservations in Unreliable P2P 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. However, the resources, e.g. storage space, CPU power and online time, provided by the peers are unreliable due to churn. In order to enable churn resistant reliable services using the resources in p2p systems, we propose in this paper a distributed mechanism termed P3R3O.KOM. The mechanism allows to reserve, monitor and use resources provided by the unreliable p2p system and maintains long-term resource reservations through controlled redundant resource provision. Evaluation shows that using KAD measurements on the prediction of the lifetime of peers allows for 100% successful reservations under churn with very low traffic overhead. This approach marks a first step for the building of a reliable p2p-based SOA and future p2p-based clouds.

Bypassing the cloud: Peer-assisted event dissemination for augmented reality games

The rising number of mobile devices and their increasing computational capabilities enable new interactive context-sensitive applications. Popular examples are augmented reality games such as Googles Ingress, where users interact with each other in the real world while being part of the game at the same time. This local interaction pattern in the real world as well as in the game is not reflected in the underlying communication pattern. Every locally generated game event is first transferred to a backend server via a cellular connection, from where it is then further disseminated to all players within the given area of interest. This communiation pattern introduces significant delays and limits the interactivity of the game. In this work, we propose an event dissemination system that exploits the locality characteristics of mobile augmented reality games to (i) enable and configure local peer-to-peer dissemination of events when appropriate and (ii) reconfigure or replace the utilized peer-to-peer protocol to adapt to a wide range of requirements. Through extensive evaluation we show that the proposed system decreases the delivery delay by a factor of eight compared to the existing communication pattern, leading to significantly increased information accuracy.

Geodemlia: A robust peer-to-peer overlay supporting location-based search

Existing peer-to-peer overlay approaches for location-based search have proven to be a valid alternative to client-server-based schemes. One of the key issues of the peer-to-peer approach is the high churn rate caused by joining and leaving peers. To address this problem, this paper proposes a new location-aware peer-to-peer overlay termed Geodemlia to achieve a robust and efficient location-based search. To evaluate Geodemlia, a real world workload model for peer-to-peer location-based services is derived from traces of Twitter. Using the workload model, a system parameter analysis of Geodemlia is conducted with the goal of finding a suitable parameter configuration. In addition, the scalability and robustness of Geodemlia is compared to a state-of-the-art tree-based approach by investigating the performance and costs of both overlays under an increasing number of peers, an increasing radius of area searches, an increasing level of churn as well as for different peer placement and search request schemes. The evaluation results reveal that in contrast to the tree-based approach, Geodemlia provides on average a 46% better success ratio as well as a 18% better recall at a moderate higher traffic overhead of 13 bytes/s and an increased average response time of 0.2 s.

PeerfactSim.KOM: Take it back to the streets

Mobile peer-to-peer networks, utilizing ad hoc communication between hand-held communication devices, serve as an alternative to cellular networks for the deployment of applications. To evaluate a new communication mechanism in mobile peer-to-peer network, simulations constitute a useful and frequently applied evaluation technique. Besides initial simulations on plain and empty maps, it is crucial to evaluate if and how the developed communication mechanism performs in the envisioned scenarios dealing with obstacles as well as node mobility. Therefore, this paper introduces a framework that provides two procedures for the creation of arbitrary environments, ranging from simple environments to complex models of cities or regions. Additionally, the framework provides different strategies to model the mobility of nodes. Together with an extended version of PeerfactSim.KOM, a simulation platform is presented that supports the complete workflow for the simulation of mobile P2P networks. The simulation platform provides (i) the modeling of purpose-based environments based on SVG-images, (ii) the modeling of realistic environments based on data from Open Street Map, as well as (iii) synthetic and realistic mobility models.

Adaptive Monitoring for Mobile Networks in Challenging Environments

The increasing capabilities of mobile communication devices are changing the way people interconnect today. Similar trends in the communication technology domain are leading to the expectation that data and media are available anytime and everywhere. A result is an increasing load on communication networks. In dynamic mobile networks that particularly rely on wireless communication such data requirements paired with environmental conditions like mobility or node density increase the risk of network failure. Consequently, monitoring is crucial in mobile networks to ensure reliable and efficient operation. Current monitoring mechanisms mostly rely on a static architecture and exhibit problems to handle the changes of mobile networks and environmental conditions over time. In this paper, an adaptive monitoring mechanism is presented to overcome these limitations. The mechanism exploits the connectivity and resource characteristics of mobile communication devices to (i) reconfigure its monitoring topology and (ii) adapt to changes of mobile networks and environmental conditions. Through evaluations we show that our proposed solution reduces the achieved relative monitoring error by a factor of six and represents a robust and reliable monitoring mechanism for these challenging environments.

BlockTree: Location-aware decentralized monitoring in mobile ad hoc networks

Mobile ad hoc networks (MANETs) represent a crucial alternative to deploy applications in urban areas. In those networks, it is inevitable that all nodes are aware of the current system state to adapt their behavior according to the varying conditions. However, existing decentralized monitoring solutions for MANETs only locate the required information at a set of nodes, which are in charge of serving the remaining network, while the availability of information depends on the accessibility of those nodes. To avoid these limitations, BlockTree is a novel, fully decentralized monitoring approach for MANETs that leverages each nodes resources to capture and distribute the system state to all nodes. Exploiting its hierarchical structure, BlockTree introduces the concept of location-aware monitoring delivering detailed as well as aggregated information. Through robust communication paired with the stateless design, BlockTree provides accurate results in the presence of fast moving nodes or over an error-prone communication medium.