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As computer networks increase in size, become more heterogeneous and span greater geographic distances, applications must be designed to cope with the very large scale, poor reliability, and often, with the extreme dynamism of the underlying network. <i>Aggregation</i> is a key functional building block for such applications: it refers to a set of functions(More)
Plain-text abstracts organized by year are available in the directory ABSTRACTS. All local authors can be reached via e-mail at the address last-name@cs.unibo.it. Questions and comments should be addressed to tr-admin@cs.unibo.it. Abstract Recent peer-to-peer (P2P) systems are characterized by decentralized control, large scale and extreme dynamism of their(More)
Aggregation - that is, the computation of global properties like average or maximal load, or the number of nodes - is an important basic functionality in fully distributed environments. In many cases - which include protocols responsible for self-organization in large-scale systems and collaborative environments - it is useful if all nodes know the value of(More)
Peer-to-peer (P2P) systems are characterized by decentralized control, large-scale and extreme dynamism of their environment. Developing applications that can cope with these characteristics requires a paradigm shift that puts adaptation, resilience and self-organization as primary concerns. Complex adaptive systems (CAS), commonly used to explain the(More)
Large-scale overlay networks have become crucial ingredients of fully-decentralized applications and peer-to-peer systems. Depending on the task at hand, overlay networks are organized into different topologies, such as rings, trees, semantic and geographic proximity networks. We argue that the central role overlay networks play in decentralized application(More)
Plain-text abstracts organized by year are available in the directory ABSTRACTS. All local authors can be reached via e-mail at the address last-name[at]cs.unibo.it. Abstract The concept of superpeer has been recently introduced to improve the performance of popular file-sharing applications. A superpeer is a node in a P2P network that operates as a server(More)
We give a formal specification and an implementation for a partitionable group communication service in asynchronous distributed systems. Our specification is motivated by the requirements for building " partition-aware " applications that can continue operating without blocking in multiple concurrent partitions and reconfigure themselves dynamically when(More)
Recent developments in information technology have brought about important changes in distributed computing. New environments such as massively large-scale, wide-area computer networks and mobile ad hoc networks have emerged. Common characteristics of these environments include extreme dynamicity, unreliability, and large scale. Traditional approaches to(More)
Among the novel metrics used to study the relative importance of nodes in complex networks, k-core decomposition has found a number of applications in areas as diverse as sociology, proteinomics, graph visualization, and distributed system analysis and design. This paper proposes new distributed algorithms for the computation of the k-core decomposition of(More)