P2P file-sharing networks such as Kazaa, eDonkey, and Limewire boast millions of users. Because of scalability concerns and legal issues, such networks are moving away from the semicentralized approach that Napster typifies toward more scalable and anonymous decentralized P2P architectures. Because they lack any central authority, these networks provide a new, interesting context for the expression of human social behavior. However, the activities of P2P community members are sometimes at odds with what real-world authorities consider acceptable. One example is the use of P2P networks to distribute illegal pornography. To gauge the form and extent of P2P-based sharing of illegal pornography, we analyzed pornography-related resource-discovery traffic in the Gnutella P2P network. We found that a small yet significant proportion of Gnutella activity relates to illegal pornography: for example, 1.6 percent of searches and 2.4 percent of responses are for this type of material. But does this imply that such activity is widespread in the file-sharing population? On the contrary, our results show that a small yet particularly active subcommunity of users searches for and distributes illegal pornography, but it isn't a behavioral norm.

Application-level overlays have emerged as a useful means of offering network services that are not supported by the underlying physical network. Most overlays employ proprietary dependability mechanisms to render them more resilient to node failure; but the use of proprietary approaches leads to duplication of effort during development and adds design complexity. In this paper we propose generic dependability services which simplify the design of overlays. Our services are fully decentralized and are configurable to take advantage of current network conditions, which can enable us to make better repairs following failures.

ABSTRACT The capabilities of the ,nodes ,which ,compose ,peer-to-peer networks vary significantly in terms of connection speed and local resources. In such an environment, it is essential that peer-to-peer systems,efficiently exploit the resources ,available on strong nodes, while at the same time allowing weaker nodes to participate in the network. To accomplish this, it is necessary to be aware of the resources available to nodes and to adapt the role that each node ,plays in the ,system. This paper gives a brief overview of RaDP2P, a framework for developing adaptive peerto-peer systems. RaDP2P uses ,a hybrid ,peer-to-peer model similar to Structella as a novel mechanism for supporting resource awareness and adaptation. Keywords Diversity; P2P; Adaptation

Peer-to-peer networks are a promising platform for supporting entirely decentralized, distributed multi-user gaming; however, multi-player games typically require highly predictable performance from the underlying network. This is at odds with the inherently unreliable nature of peer-to-peer environments. Existing approaches to providing peer-to-peer support for multi- player gaming focus on compensating for the unpredictability of the underlying network. We propose that rather than trying to compensate for these factors, they can be exploited together with information about the peer-to-peer network in order to address the problem of maintaining a novel gaming experience in the absence of a central authority. In order to explore our proposition, we model the measurable properties of P2P networks within a distributed multi-player game - Net World. We do this is such a way that the heterogeneous and unpredictable nature of the peer- to-peer environment becomes a positive part of the players experience.

A new analysis of free riding on the Gnutella network updates data from 2000 and points to an increasing downgrade in the network's overall performance and the emergence of a "metatragedy" of the commons. Individuals who use peer-to-peer (P2P) file-sharing networks such as Gnutella face a social dilemma. They must decide whether to contribute to the common good by sharing files or maximize their personal experience by free riding, downloading files while not contributing any to the network. Individuals gain no personal benefits from uploading files (in fact, it's inconvenient), so it's "rational" for users to free ride. However, significant numbers of free riders degrade the entire system's utility, creating a "tragedy of the digital commons."

There has been a significant body of research conducted into various structured and unstructured overlay network protocols. Both paradigms have advantages for specific application domains and researchers are beginning to examine the benefits of using hybridized systems. We hypothesize that resource awareness and adaptation are essential to the efficient exploitation of the resources available on the diverse nodes which compose peer-to-peer networks. To support this, we propose a hybrid peer-to-peer model which uses an unstructured decentralised network layered on top of a structured overlay to provide support for multiple levels of adaptation.

Thorough testing of distributed systems, particularly peer-to-peer systems can prove difficult due to the problems inherent in deploying, controlling and monitoring many nodes simultaneously. This problem will only increase as the scale of distributed systems continues to grow. This framework implements a test bed environment using a semi-centralized peer-to-peer network as a substrate for sharing resources made available from standard PCs. This framework automates the process of test-case deployment using a combination of reflection and aspect oriented programming. This allows 'point-and-click' publishing of software onto the test-bed. Our framework also provides a common monitoring, control and logging interface for all nodes running on the network. Together, these features greatly reduce deployment-time for real-world test scenarios. Automated insertion and removal of test code also ensures that the testing process does not compromise the correctness of the final system.

Peer-to-peer environments are highly heterogeneous and are likely to become more so due to the proliferation of mobile Internet access technologies and the development of novel peer-topeer applications. Adaptation is essential in such heterogeneous systems in order to exploit the resources available on diverse nodes and tailor network services to meet the needs of diverse applications. We argue that existing support for resource awareness and adaptation in peer-to-peer systems is inadequate and we propose a framework for developing peer-to-peer systems with generic and extensible support for resource awareness and adaptation. A hybrid peer-to-peer model similar to Structella is used in this framework as a novel mechanism for supporting resource awareness and adaptation.

There has been a significant body of research conducted into various structured and unstructured overlay network protocols. Both paradigms have advantages for specific application domains and researchers are beginning to examine the benefits of using hybridized systems. We hypothesize that resource awareness and adaptation are essential to the efficient exploitation of the resources available on the diverse nodes which compose peer-to-peer networks. To support this, we propose a hybrid peer-topeer model which uses an unstructured decentralised network layered on top of a structured overlay to provide support for multiple levels of adaptation. This model will improve quality of service for traditional peer-to-peer systems and provide support for novel next generation peer-to-peer applications.

The first generation of peer-to-peer file sharing systems followed the traditional client-server paradigm. However, legality and scalability issues have driven the development of decentralized file sharing protocols; the most popular of these being Gnutella. To date, such systems have been unable to match the Quality of Service (Qos) offered by centralized architectures. AGnuS improves QoS on Gnutella by increasing file availability, improving network friendliness and increasing file quality. This is achieved by layering caching, load balancing, content-based routing and filtering services on top of the core Gnutella protocol.

Testing is a vital stage in the development cycle of any application but is often neglected due to the difficulty and expense to perform the stage successfully. This is especially so for distributed applications due to the coordination required to successfully test several distributed components simultaneously. This position paper proposes a framework implemented using Aspect-Oriented Programming and Reflection, which aims to ease the testing of such systems and other varieties of systems which encounter similar problems. Two case-studies are examined to illustrate how the framework will simplify the testing stage.