Structures and Algorithms for Peer-to-Peer Cooperation

Peer-to-peer overlay networks are distributed systems, without any hierarchical organization or centralized control. Peers form self-organizing overlay networks that are on top of the Internet. Both parts of this thesis deal with peer-to-peer overlay networks, the first part with unstructured ones used to build a large scale Networked Virtual Environment. The second part gives insights on how the users of a real life structured peer-to-peer network behave, and how well the proposed algorithms for publishing and retrieving data work. Moreover we analyze the security (holes) in such a system. Networked virtual environments (NVEs), also known as distributed virtual environments, are computer-generated, synthetic worlds that allow simultaneous interactions of multiple participants. Many efforts have been made to allow people to interact in realistic virtual environments, resulting in the recent boom of Massively Multiplayer Online Games. In the first part of the thesis, we present a complete study of an augmented Delaunay-based overlay for peer-to-peer shared virtual worlds. We design an overlay network matching the Delaunay triangulation of the participating peers in a generalized d-dimensional space. Especially, we describe the self-organizing algorithms for peer insertion and deletion. To reduce the delay penalty of overlay routing, we propose to augment each node of the Delaunay-based overlay with a limited number of carefully selected shortcut links creating a small-world. We show that a small number of shortcuts is sufficient to significantly decrease the delay of routing in the space. We present a distributed algorithm for the clustering of peers. The algorithm is dynamic in the sense that whenever a peer joins or leaves the NVE, the clustering will be adapted if necessary by either splitting a cluster or merging clusters. The main idea of the algorithm is to classify links between adjacent peers into short intracluster and long inter-cluster links. In a structured system, the neighbor relationship between peers and data locations is strictly defined. Searching in such systems is therefore determined by the particular network architecture. Among the strictly structured systems, some implement a distributed hash table (DHT) using different data structures. DHTs have been actively studied in the literature and many different proposals have been made on how to organize peers in a DHT. However, very few DHTs have been implemented in real systems and deployed on a large scale. One exception is KAD, a DHT based on Kademlia, which is part of eDonkey, a peer-to-peer file sharing system with several million simultaneous users. In the second part of this thesis we give a detailed background on KAD, the organization of the peers, the search and the publish operations, and we describe our measurement methodology. We have been crawling KAD continuously for more than a year. We obtained information about geographical distribution of peers, session times, peer availability, and peer lifetime. We found that session times are Weibull distributed and show how this information can be exploited to make the publishing mechanism much more efficient. As we have been studying KAD over the course of the last two years we have been both, fascinated and frightened by the possibilities KAD offers. We show that mounting a Sybil attack is very easy in KAD and allows to compromise the privacy of KAD users, to compromise the correct operation of the key lookup and to mount distributed denial-of-service attacks with very little resources

Integration, management and communication of heterogeneous design resources with WWW technologies

Recently, advanced information technologies have opened new pos-sibilities for collaborative designs. In this paper, a Web-based collaborative de-sign environment is proposed, where heterogeneous design applications can be integrated with a common interface, managed dynamically for publishing and searching, and communicated with each other for integrated multi-objective de-sign. The CORBA (Common Object Request Broker Architecture) is employed as an implementation tool to enable integration and communication of design application programs; and the XML (eXtensible Markup Language) is used as a common data descriptive language for data exchange between heterogeneous applications and for resource description and recording. This paper also intro-duces the implementation of the system and the encapsulating issues of existing legacy applications. At last, an example of gear design based on the system is il-lustrated to identify the methods and procedure developed by this research

An Experimental Nexos Laboratory Using Virtual Xinu

The Nexos Project is a joint effort between Marquette University, the University of Buffalo, and the University of Mississippi to build curriculum materials and a supporting experimental laboratory for hands-on projects in computer systems courses. The approach focuses on inexpensive, flexible, commodity embedded hardware, freely available development and debugging tools, and a fresh implementation of a classic operating system, Embedded Xinu, that is ideal for student exploration. This paper describes an extension to the Nexos laboratory that includes a new target platform composed of Qemu virtual machines. Virtual Xinu addresses two challenges that limit the effectiveness of Nexos. First, potential faculty adopters have clearly indicated that even with the current minimal monetary cost of installation, the hardware modifications, and time investment remain troublesome factors that scare off interested educators. Second, overcoming the inherent complications that arise due to the shared subnet that result in students\u27 projects interfering with each other in ways that are difficult to recreate, debug, and understand. Specifically, this paper discusses porting the Xinu operating systems to Qemu virtual hardware, developing the virtual networking platform, and results showing success using Virtual Xinu in the classroom during one semester of Operating Systems at the University of Mississippi

Efficient data representation for XML in peer-based systems

Purpose - New directions in the provision of end-user computing experiences mean that the best way to share data between small mobile computing devices needs to be determined. Partitioning large structures so that they can be shared efficiently provides a basis for data-intensive applications on such platforms. The partitioned structure can be compressed using dictionary-based approaches and then directly queried without firstly decompressing the whole structure. Design/methodology/approach - The paper describes an architecture for partitioning XML into structural and dictionary elements and the subsequent manipulation of the dictionary elements to make the best use of available space. Findings - The results indicate that considerable savings are available by removing duplicate dictionaries. The paper also identifies the most effective strategy for defining dictionary scope. Research limitations/implications - This evaluation is based on a range of benchmark XML structures and the approach to minimising dictionary size shows benefit in the majority of these. Where structures are small and regular, the benefits of efficient dictionary representation are lost. The authors' future research now focuses on heuristics for further partitioning of structural elements. Practical implications - Mobile applications that need access to large data collections will benefit from the findings of this research. Traditional client/server architectures are not suited to dealing with high volume demands from a multitude of small mobile devices. Peer data sharing provides a more scalable solution and the experiments that the paper describes demonstrate the most effective way of sharing data in this context. Social implications - Many services are available via smartphone devices but users are wary of exploiting the full potential because of the need to conserve battery power. The approach mitigates this challenge and consequently expands the potential for users to benefit from mobile information systems. This will have impact in areas such as advertising, entertainment and education but will depend on the acceptability of file sharing being extended from the desktop to the mobile environment. Originality/value - The original work characterises the most effective way of sharing large data sets between small mobile devices. This will save battery power on devices such as smartphones, thus providing benefits to users of such devices

Document Archiving, Replication and Migration Container for Mobile Web Users

With the increasing use of mobile workstations for a wide variety of tasks and associated information needs, and with many variations of available networks, access to data becomes a prime consideration. This paper discusses issues of workstation mobility and proposes a solution wherein the data structures are accessed in an encapsulated form - through the Portable File System (PFS) wrapper. The paper discusses an implementation of the Portable File System, highlighting the architecture and commenting upon performance of an experimental system. Although investigations have been focused upon mobile access of WWW documents, this technique could be applied to any mobile data access situation.Comment: 5 page

Self-organizing peer-to-peer social networks

This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2008 The Authors.Peer-to-peer (P2P) systems provide a new solution to distributed information and resource sharing because of its outstanding properties in decentralization, dynamics, flexibility, autonomy, and cooperation, summarized as DDFAC in this paper. After a detailed analysis of the current P2P literature, this paper suggests to better exploit peer social relationships and peer autonomy to achieve efficient P2P structure design. Accordingly, this paper proposes Self-organizing peer-to-peer social networks (SoPPSoNs) to self-organize distributed peers in a decentralized way, in which neuron-like agents following extended Hebbian rules found in the brain activity represent peers to discover useful peer connections. The self-organized networks capture social associations of peers in resource sharing, and hence are called P2P social networks. SoPPSoNs have improved search speed and success rate as peer social networks are correctly formed. This has been verified through tests on real data collected from the Gnutella system. Analysis on the Gnutella data has verified that social associations of peers in reality are directed, asymmetric and weighted, validating the design of SoPPSoN. The tests presented in this paper have also evaluated the scalability of SoPPSoN, its performance under varied initial network connectivity and the effects of different learning rules.National Natural Science of Foundation of Chin

Sharing large data collections between mobile peers

New directions in the provision of end-user computing experiences mean that we need to determine the best way to share data between small mobile computing devices. Partitioning large structures so that they can be shared efficiently provides a basis for data-intensive applications on such platforms. In conjunction with such an approach, dictionary-based compression techniques provide additional benefits and help to prolong battery life

Evaluation of an awareness distribution mechanism: a simulation approach

In distributed software engineering, the role of informal communication is frequently overlooked. Participants simply employ their own ad-hoc methods of informal communication. Consequently such communication is haphazard, irregular, and rarely recorded as part of the project documentation. Thus, a need for tool support to facilitate more systematic informal communication via awareness has been identified. The tool proposed is based on the provision of awareness support that recognises the complete context of the evolution of software artefacts rather than single events. Peer-to-Peer (P2P) networking has been successfully employed to develop various distributed software engineering support tools. However, there are scalability problems inherent in naive P2P networks. To this end a semantic overlay network organisation algorithm has been developed and tested in simulation prior to deployment as part of a forthcoming awareness extension to the Eclipse environment. The simulation verified that the self-organisation algorithm was suitable for arranging a P2P network, but several unexpected behaviours were observed. These included wandering nodes, starved nodes, and local maxima. Each of these problems required modification of the original algorithm design to solve or ameliorate them