Otso Kassinen

Performance evaluation of a Kademlia-based communication-oriented P2P system under churn

The phenomenon of churn has a significant effect on the performance of Peer-to-Peer (P2P) networks, especially in mobile environments that are characterized by intermittent connections and unguaranteed network bandwidths. A number of proposals have been put forward to deal with this problem; however, we have so far not seen any thorough analysis to guide the optimal design choices and parameter configurations for structured P2P networks. In this article, we present a performance evaluation of a structured communication-oriented P2P system in the presence of churn. The evaluation is conducted using both simulation models and a real-life prototype implementation. In both evaluation environments, we utilize Kademlia with some modifications as the underlying distributed hash table (DHT) algorithm, and Peer-to-Peer Protocol (P2PP) as the signaling protocol. The results from the simulation models created using Nethawk EAST (a telecommunication simulator software) suggest that, in most situations, a lookup parallelism degree of 3 and resource replication degree of 3 are enough for guaranteeing a high resource lookup success ratio. We also notice that, with the parallel lookup mechanism, a good success ratio is achieved even without the KeepAlive traffic that is used for detecting the aliveness of nodes. A prototype system that works in mobile environment is implemented to evaluate the feasibility of mobile nodes acting as full-fledged peers. The measurements made using the prototype show that, from the viewpoints of CPU load and network traffic load, it is feasible for the mobile nodes to take part in the overlay. Through energy consumption measurements, we draw the conclusion that in general the UMTS access mode consumes slightly more power than the WLAN access mode. Protocol packets with sizes of 200bytes or less are observed to be the most energy efficient in the UMTS access mode.

Energy consumption model for mobile devices in 3G and WLAN networks

In this paper, we propose an advanced model, called e-Aware, for estimating how application layer protocol properties affect the energy consumption of mobile devices, operating in 3G (WCDMA) and WLAN (802.11) networks. The main motivation for the model is to facilitate designing energy-efficient networking solutions, by reducing the need for time-consuming measurements with real-life networks and devices. The model makes a distinction between signaling and media transfers due to their different energy consumption characteristics, and takes into account the fundamentals of radio interface properties, such as different energy states and timers controlling them. The model is fine-tuned using device-specific coefficients that are defined according to real-world measurements with actual devices. We have implemented the model and simulated it in Matlab environment. The correct functionality is verified by comparing the results with real-life measurements in identical networking scenarios.

Towards Context-Aware Mobile Web 2.0 Service Architecture

The emergence of new lightweight Web technologies and the development of mobile devices leads to a situation, where the users can consume the same Web services regardless of the place, time and device. Mobile devices are equipped with networking capabilities and sensors that provide versatile context and user-community information. This information enhances the user experience as it can be used to compensate the limited means of input. We present a context-aware mobile Web 2.0 service architecture that connects user context and community information with the Web services. This convergence enables the development of device-independent services that are enriched and personalized with user context and community information. Mobile middleware may be needed for efficient delivery of this information from the mobile device to the Web services. Four novel communication models for the delivery are introduced, namely centralized control, centralized services, peer-to-peer services, and pure peer-to-peer. The purpose of the models is to offer a secure and reliable platform for creating new services. Finally, we study virtual communities and market structures of the proposed models from a multidisciplinary point of view. We claim that the selected technical model determines the prospective market structure.

Battery life of mobile peers with UMTS and WLAN in a Kademlia-based P2P overlay

We evaluate the battery life of mobile devices that act as full-fledged peer nodes in a Kademlia DHT based P2P overlay network. The motivation is to find out how long a mobile peer is able to function in a UMTS or WLAN access network, and how the different parameter settings affect this battery life; this is interesting as mobile access to P2P networks is expected to become common in the near future. The majority of the peers in an overlay are simulated on a server array, while the power measurements are conducted on actual mobile devices. The variable overlay parameters are the number of peers, resource lookup activity, and the level of churn. The chosen values of parameters represent a relatively high amount of activity. In UMTS the measured battery life is approximately 3 hours and in WLAN it is 5 to 10 (most often around 8) hours. We also provide power measurements on sending and receiving UDP packets in UMTS and WLAN, for approximating the power consumption of network protocols without protocol-specific measurements.

Feasibility evaluation of a communication-oriented P2P system in mobile environments

We present the feasibility evaluation of a structured communication-oriented Peer-to-Peer (P2P) system being used in mobile environments in this paper. The different levels of churn are modeled by the exponential distribution with varied value of mean online time. Our system utilizes Kademlia with some modifications as the underlying Distributed Hash Table (DHT) algorithm, and Peer-to-Peer Protocol (P2PP), one of the former candidates of Peer-to-Peer Session Initiation Protocol (P2PSIP) working group, as the signaling protocol. A prototype is implemented to evaluate the feasibility of mobile nodes acting as fully fledged peers. The prototype measurements show it is feasible for the mobile nodes to take part in the overlay from the viewpoints of CPU load and network traffic load. Through battery measurements, we draw the conclusion that the UMTS access mode consumes slightly more power than the WLAN access mode in general. Protocol packets with sizes of 200 bytes or less are observed to be the most energy efficient in the UMTS access mode.

Group-based content push with dynamic session startup

This paper proposes an intelligent mobile middleware utilizing group-based content push with dynamic session startup and plug-and-play features. Solution enhances the distribution of mobile content, such as game applications or multimedia files, within a peer group community. It exploits the social relationships of the user community to enable instant application downloading, installation, and licensing upon incoming connection attempt initiated by another peer group member. In the core of the middleware functionality are dynamic application identification and immediate session startup. This paper presents a use case scenario for a content push procedure. Functional and technical analysis of the novel middleware component are provided. Observations from experimental signaling system setup are mapped with estimates of end-to-end delay budget.

P2P group management systems: A conceptual analysis

Peer-to-Peer (P2P) networks are becoming eminent platforms for both distributed computing and interpersonal communication. Their role in contemporary multimedia content delivery and communication systems is strong, as witnessed by many popular applications and services. Groups in P2P systems can originate from the relations between humans, or they can be defined with purely technical criteria such as proximity. In this article, we present a conceptual analysis of P2P group management systems. We illustrate how groups are formed using different P2P system architectures, and analyze the advantages and disadvantages of using each P2P system architecture for implementing P2P group management. The evaluation criteria in the analysis are performance, robustness, fairness, suitability for battery-powered devices, scalability, and security. The outcome of the analysis facilitates the selection of an appropriate P2P system architecture for implementing P2P group management in both further research and prototype development.

Top-Down Connectivity Policy Framework for Mobile Peer-to-Peer Applications

Selection of optimal network connectivity in mobile telecommunications is an important field of study. There are more parameters to consider than mere selection of physical connectivities. For optimal vertical connectivity selections, a cross-layer approach is needed. This paper presents a formulation for the Holistic Connectivity framework, which, when applied in a mobile middleware solution, enables seamless top-down connectivity management in mobile consumer products. The solution has emphasis on peer-to-peer networking. Connectivity policy management extends the context-aware connectivity management framework developed earlier at the University of Oulu, Finland. Technical and functional scenarios for the proposed framework are discussed, and preliminary experimental results with realtime traffic are provided for supporting further design and requirement specification.

Analysis of Concept and Incentives for Digital Content Superdistribution

Despite the huge popularity of peer-to-peer distribution and yet again growing interest towards superdistribution, there is no consensus among researchers regarding the appropriate definition of superdistribution or its different types. There is a similar lack of consistence in the definition of the relation between superdistribution and peer-to-peer distribution. The objective of this paper is to develop a classification system for superdistribution that is useful to researchers from various disciplinary perspectives and takes into account the different ways how superdistribution can be realized. We also present some statistics about general acceptance of superdistribution as a distribution method for commercial and user-created content.

Effects of peer-to-peer overlay parameters on mobile battery duration and resource lookup efficiency

This paper evaluates the feasibility of mobile nodes as peers in a structured peer-to-peer overlay network. Our performance analysis is based on the Peer-to-Peer Protocol (P2PP), which is a peer protocol candidate for the Peer-to-Peer Session Initiation Protocol (P2PSIP). We use both, live-network measurements and simulations, to evaluate two performance metrics: resource lookup success rate and mobile battery duration. While lookup success rate measures P2PP performance in general, battery duration is crucial for mobile use of P2PP. Restricted battery life limits the feasibility of mobile peers. We reveal the tradeoff between lookup success rate and battery duration. Based on the findings it is possible to find more suitable protocol parameters for mobile peers. The battery duration measurements, made with UDP in UMTS and WLAN access networks, are also applicable in the wireless usage of other application-layer protocols.