P2P Computing Concepts and Their Discussions

In this chapter, we discuss P2P systems that have been deployed in file sharing and real-time media streaming. We discuss the limitations of the implementations for existing P2P-based file sharing and media streaming applications in detail. More advanced resource reciprocation strategies, where peers make foresighted decisions on their resource distribution in a way that maximizes their cumulative utilities are discussed.

Existing shared object spaces cannot be used to build large scale distributed systems as their realizations do not scale up. Inefficient mechanisms for handling failures and object lookups, use of centralized components as well as inability to operate without global knowledge inhibit their scalability. This paper proposes a platform named Virat that focuses on the integration of shared object spaces with Peer-to-Peer (P2P) systems. Virat provides a shared object space abstraction over a wide area distributed system. It is built using a unique two-layered P2P architecture that combines the advantages of structured and unstructured P2P systems. Virat is a platform over which collaborative data sharing services can be provided from the edges of the Internet. We also present extensive performane studies to demonstrate that Virat can outperform centralized shared object spaces and performs as good, if not better than OpenDHT, a state of the art P2P shared storage space, in both Intranet and Internet test beds.

European Transactions on Telecommunications, 2004

Peer-to-peer (P2P) services evolved to the most popular applications in today's Internet. In particular, P2P networks became very popular amid the relentless spread of Gnutella, Kazaa, eDonkey and BitTorrent file sharing applications. Remarkably, only very simple protocols and almost no support by the transport network was required to make these distributed services operable on a large scale in very little time. P2P entails a highly attractive paradigm in distributed computing: P2P is based on communication between equals. The peers are highly autonomous. P2P services provide simple and efficient mechanisms to pool and share exchangeable resources like CPU cycles, disk space or content. These features facilitate that any peer can be removed without resulting in a complete loss of service, in contrast to the traditional client/server concept, where a failure of the central control entity may corrupt the service completely. A further reason for the notable success of P2P is that these networks operate on the application level and typically form application-specific overlays. P2P overlays work without particular network or transport support, and can be run completely at the edge of a network. They apply self-organizing principles and special routing schemes to locate and exchange resources. While P2P overlays do implement a certain type of group communication structure, they do not suffer from the same deployment difficulties as multicast services did in the past. The P2P mode of operation however, also has some downsides. P2P protocols cause higher traffic volumes, including data traffic as well as signaling traffic, since the peers need to synchronize. P2P network topologies reveal high variability and traffic patterns of P2P applications fluctuate considerably in time and space. Traditional network design techniques and traffic engineering procedures have to be validated to work in the P2P context before they are applied. New engineering methods may be required in order to maintain the autonomous and self-organizing characteristics of P2P and to provide appropriate service stability, quality and efficiency for P2P services. The aim of this special issue of the European Transactions on Telecommunication is to present very recent, outstanding research work on P2P networks and P2P services. The Call for Paper resulted in the submission of 42 papers from Europe, the United States and the Asian-Pacific region. The editor team has selected eight of these submissions after a thorough review process and extensive discussions for publication in this special issue. The guest editor team of this ETT special issue would also like to thank the publisher, the reviewers and the authors for their efforts and flexibility to produce, review and finalize this special issue in a very short time frame. We hope that this special issue may serve to promote further research in this new and popular area of telecommunication. The contribution of Azzouna and Guillemin evaluates the impact of P2P applications on traffic in wide area networks. The authors analyze measurements taken on a high speed IP backbone link carrying P2P applications traffic towards several ADSL areas. They observe that the prevalent part, the traffic is caused by P2P applications (almost 80% of total traffic) and that the usage of network becomes highly symmetric. Since long lasting TCP connections of P2P applications have a rather small bit rate and do not show evidence for long range dependency, the global traffic can be described by means of usual teletraffic models based on M=G=1 queues with Weibullian service times. The paper of Schollmeier and Schollmeier investigates P2P traffic by a graph theoretical study of the properties of P2P overlays. Analytical topology models for infinite and finite random networks are used to derive performance characteristics for P2P protocols and to evaluate the effect of introducing centralized entities, such as superpeers. Cholvi, Felber and Biersack propose novel mechanisms for improving the search efficiency in unstructured P2P networks. The mechanism is based on peers performing local dynamic topology adaptations, which are derived from query traffic patterns. The topology adaptation creates spontaneously semantic communities, i.e. groups of peers that share similar interests, in which file requests are fulfilled more efficiently. Copyright # 2004 AEI Wierzbicki et al. investigate the possibility of caching of files in P2P file sharing applications. They show that the file popularity in P2P file sharing networks does not follow Zipf's law and that P2P file sharing traffic differs strongly from well-studied web traffic. The results are used to investigate the efficiency of different cache management policies for the FastTrack P2P file sharing protocol. Sasabe et al. investigate scalable media search and in-time retrieval methods based on a P2P network architecture. The method is able to achieve continuous media play-out for popular media streams without introducing extra load on the system. The authors also investigate the failure of LRU cache replacement algorithms for continuous media play-out of unpopular media streams and propose a biological-inspired cache replacement mechanism that considers the balance between supply and demand for media streams. The algorithm can adapt easily to changes in the popularity of media streams. Kumar et al. present a P2P network based on a butterfly overlay topology. The diameter of this overlay achieves a theoretical lower bound of log n=log n log n, if the average routing table size is not more than log n. Compared to existing DHT schemes, the diameter is reduced by a factor of log log n. This reduction translates into the same amount of reduction on query latency and average traffic per node. The authors show that the proposed scheme maintains the same level of robustness as existing DHT schemes. Yamada, Hoshiai and Kimura propose brokerless trust and reputation mechanisms for the COMNet P2P framework. COMNet is an intelligent community spaces architecture, which supports the activation of communities through P2P technology. The proposed trust and reputation algorithms are solely based on information from other peers. Bisignano, Di Modica and Tomarchio present a framework for mobile P2P applications, which combines P2P ad hoc communication with the capabilities of small mobile units. The framework is designed for J2ME enabled mobile devices in an infrastructure-less environment. One of the key features of the framework is the interoperability with JXTA, a wellknown P2P open platform. A simple but effective example of application is provided showing the viability of the designed framework.

Proceedings 22nd International Conference on Distributed Computing Systems Workshops, 2002

Peer-to-peer systems recently captured the attention of practitioners and researchers as they provide an attractive alternative to client-server architectures. Peerto-peer enables the creation of massively distributed networks of data repositories that can be setup and discarded easily according to applicative needs. Nevertheless, the current popularity of these systems is due mostly to their use for file sharing over the Internet.

2010

Peer-to-Peer (P2P) systems have been invented, deployed and researched for more than ten years and went far beyond the simple file sharing applications. In P2P networks, participants organize themselves in an overlay network that abstracts from the topological characteristics of the underlying physical network. Aim of these systems is the distribution of some kind of resources like contents, storage, or CPU cycles. Users, therefore, play an active role so that they can be considered as client and server at the same time, for the particular service that is provided through the P2P paradigm.