3,087 research outputs found
Programming Idioms for Transactional Events
Transactional events (TE) are an extension of Concurrent ML (CML), a
programming model for synchronous message-passing. Prior work has focused on
TE's formal semantics and its implementation. This paper considers programming
idioms, particularly those that vary unexpectedly from the corresponding CML
idioms. First, we solve a subtle problem with client-server protocols in TE.
Second, we argue that CML's wrap and guard primitives do not translate well to
TE, and we suggest useful workarounds. Finally, we discuss how to rewrite CML
protocols that use abort actions
An Optimal Trade-off between Content Freshness and Refresh Cost
Caching is an effective mechanism for reducing bandwidth usage and
alleviating server load. However, the use of caching entails a compromise
between content freshness and refresh cost. An excessive refresh allows a high
degree of content freshness at a greater cost of system resource. Conversely, a
deficient refresh inhibits content freshness but saves the cost of resource
usages. To address the freshness-cost problem, we formulate the refresh
scheduling problem with a generic cost model and use this cost model to
determine an optimal refresh frequency that gives the best tradeoff between
refresh cost and content freshness. We prove the existence and uniqueness of an
optimal refresh frequency under the assumptions that the arrival of content
update is Poisson and the age-related cost monotonically increases with
decreasing freshness. In addition, we provide an analytic comparison of system
performance under fixed refresh scheduling and random refresh scheduling,
showing that with the same average refresh frequency two refresh schedulings
are mathematically equivalent in terms of the long-run average cost
A security analysis of version 2 of the Network Time Protocol (NTP): A report to the privacy and security research group
The Network Time Protocol is being used throughout the Internet to provide an accurate time service. The security requirements are examined of such a service, version 2 of the NTP protocol is analyzed to determine how well it meets these requirements, and improvements are suggested where appropriate
Parallel Deferred Update Replication
Deferred update replication (DUR) is an established approach to implementing
highly efficient and available storage. While the throughput of read-only
transactions scales linearly with the number of deployed replicas in DUR, the
throughput of update transactions experiences limited improvements as replicas
are added. This paper presents Parallel Deferred Update Replication (P-DUR), a
variation of classical DUR that scales both read-only and update transactions
with the number of cores available in a replica. In addition to introducing the
new approach, we describe its full implementation and compare its performance
to classical DUR and to Berkeley DB, a well-known standalone database
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