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The number of software applications available on the Internet for distributing video streams in real time over P2P networks has grown quickly in the last two years. Typical this kind of distribution is made by television channel broadcasters which try to make their content globally available, using viewer's resources to support a large scale distribution of video without incurring in incremental costs...
In this paper we investigate the problem of speculative processing in a replicated transactional system layered on top of an optimistic atomic broadcast service. We consider a realistic model in which transactions' read/write sets are not known a-priori, and transactions' data access patterns may vary depending on the observed snapshot. We formalize a set of correctness and optimality properties aimed...
At current date the problem of how to build distributed and replicated software transactional memory (STM) to enhance both dependability and performance is still largely unexplored. This paper fills this gap by presenting D2STM, a replicated STM whose consistency is ensured in a transparent manner, even in the presence of failures. Strong consistency is enforced at transaction commit time by a non-blocking...
Gossip, or epidemic, protocols have emerged as a highly scalable and resilient approach to implement several application level services such as reliable multicast, data aggregation, publish-subscribe, among others. All these protocols organize nodes in an unstructured random overlay network. In many cases, it is interesting to bias the random overlay in order to optimize some efficiency criteria,...
The Weak Mutual Exclusion (WME) is a recently proposed abstraction which, analogously to classical Distributed Mutual Exclusion (DME), permits to serialize concurrent accesses to a shared resource. Unlike DME, however, the WME abstraction regulates the access to a replicated shared resource and is solvable in the presence of less restrictive synchrony assumptions, i.e. in an asynchronous system augmented...
The increasing scale and complexity of distributed system motivates the need for autonomous management. One of the key aspects in the management of distributed systems is the issue of component monitoring. Component monitoring is particularly challenging in large-scale dynamic systems, given the need to ensure that each component is monitored by at least one non-faulty component, despite joins, leaves,...
This paper proposes a novel database replication algorithm that offers strong consistency (linearizable semantics) and allows reads and non-conflicting writes to execute in parallel in multiple replicas. The proposed algorithm supports the use of quorums to trade the availability/efficiency of read and write operations, making a bridge between consensus-based and quorum based solutions for database...
There is an inherent trade-off between epidemic and deterministic tree-based broadcast primitives. Tree-based approaches have a small message complexity in steady-state but are very fragile in the presence of faults. Gossip, or epidemic, protocols have a higher message complexity but also offer much higher resilience. This paper proposes an integrated broadcast scheme that combines both approaches...
Gossip, or epidemic, protocols have emerged as a powerful strategy to implement highly scalable and resilient reliable broadcast primitives. Due to scalability reasons, each participant in a gossip protocol maintains a partial view of the system. The reliability of the gossip protocol depends upon some critical properties of these views, such as degree distribution and clustering coefficient. Several...
Today's mobile applications need to execute in a wide range of heterogeneous devices that operate in different conditions. In this context, dynamic adaptation of the underlying communication support is fundamental to achieve adequate performance. We address the problem of supporting dynamic adaptation of communication protocol stacks through a policy-oriented approach, which promotes the separation...
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