Deborah A. Agarwal

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Fault-tolerant distributed systems are becoming more important, but in existing systems, maintaining the consistency of replicated data is quite expensive. The Totem single-ring protocol supports consistent concurrent operations by placing a total order on broadcast messages. This total order is derived from the sequence number in a token that circulates(More)
We formulate a model of extended virtual synchrony that deenes a group communication transport service for multicast and broadcast communication in a distributed system. The model extends the virtual synchrony model of the Isis system to support continued operation in all components of a partitioned network. The signiicance of extended virtual synchrony is(More)
Many applications can benefit from distributed systems based on multiple computers interconnected by a communication network. Distributed systems use inexpensive high-performance computers and can be configured closely to the application. Information can be replicated on several processors to improve performance and to provide fault tolerance. However,(More)
Many protocols exist to support the maintenance of consistency of data in fault-tolerant distributed systems ; these protocols are quite expensive and thus have not been widely adopted. The Totem protocol supports consistent concurrent operations by placing a total order on broadcast messages. This total order is achieved by including a sequence number in a(More)
The Totem multiple-ring protocol provides reliable totally ordereddelivery of messages across multiple local-area networks interconnectedby gateways. This consistent message order is maintained in the presenceof network partitioning and remerging, and of processor failure andrecovery. The protocol provides accurate topology change information aspart of the(More)
Distributed applications require information to effectively utilize the network. Some of the information they require is the current and maximum bandwidth, current and minimum latency, bottlenecks, burst frequency, and congestion extent. This type of information allows applications to determine parameters like optimal TCP buffer size. In this paper, we(More)
The combination of low-cost sensors, low-cost commodity computing, and the Internet is enabling a new era of data-intensive science. The dramatic increase in this data availability has created a new challenge for scientists: how to process the data. Scientists today are envisioning scientific computations on large scale data but are having difficulty(More)
Many distributed applications require a secure reliable group communication system to provide coordination among the application components. This paper describes a secure group layer (SGL) which bundles a reliable group communication system, a group authorization and access control mechanism, and a group key agreement protocol to provide a comprehensive and(More)
The Totem system supports fault-tolerant applications in which distributed processes cooperate to perform a commontask and in which replicated data must be updated consistently in the presence of asynchrony and faults. Reliable totally ordered delivery of messages to processes within process groups is provided on a single local-area network or over multiple(More)
It can be natural to believe that many of the traditional issues of scale have been eliminated or at least greatly reduced via cloud computing. That is, if one can create a seemingly wellfunctioning cloud application that operates correctly on small or moderate-sized problems, then the very nature of cloud programming abstractions means that the same(More)