13,909 research outputs found
2 P2P or Not 2 P2P?
In the hope of stimulating discussion, we present a heuristic decision tree
that designers can use to judge the likely suitability of a P2P architecture
for their applications. It is based on the characteristics of a wide range of
P2P systems from the literature, both proposed and deployed.Comment: 6 pages, 1 figur
Statistical Classification of Cascading Failures in Power Grids
We introduce a new microscopic model of the outages in transmission power
grids. This model accounts for the automatic response of the grid to load
fluctuations that take place on the scale of minutes, when the optimum power
flow adjustments and load shedding controls are unavailable. We describe
extreme events, initiated by load fluctuations, which cause cascading failures
of loads, generators and lines. Our model is quasi-static in the causal,
discrete time and sequential resolution of individual failures. The model, in
its simplest realization based on the Directed Current description of the power
flow problem, is tested on three standard IEEE systems consisting of 30, 39 and
118 buses. Our statistical analysis suggests a straightforward classification
of cascading and islanding phases in terms of the ratios between average number
of removed loads, generators and links. The analysis also demonstrates
sensitivity to variations in line capacities. Future research challenges in
modeling and control of cascading outages over real-world power networks are
discussed.Comment: 8 pages, 8 figure
Micro-CernVM: Slashing the Cost of Building and Deploying Virtual Machines
The traditional virtual machine building and and deployment process is
centered around the virtual machine hard disk image. The packages comprising
the VM operating system are carefully selected, hard disk images are built for
a variety of different hypervisors, and images have to be distributed and
decompressed in order to instantiate a virtual machine. Within the HEP
community, the CernVM File System has been established in order to decouple the
distribution from the experiment software from the building and distribution of
the VM hard disk images.
We show how to get rid of such pre-built hard disk images altogether. Due to
the high requirements on POSIX compliance imposed by HEP application software,
CernVM-FS can also be used to host and boot a Linux operating system. This
allows the use of a tiny bootable CD image that comprises only a Linux kernel
while the rest of the operating system is provided on demand by CernVM-FS. This
approach speeds up the initial instantiation time and reduces virtual machine
image sizes by an order of magnitude. Furthermore, security updates can be
distributed instantaneously through CernVM-FS. By leveraging the fact that
CernVM-FS is a versioning file system, a historic analysis environment can be
easily re-spawned by selecting the corresponding CernVM-FS file system
snapshot.Comment: Conference paper at the 2013 Computing in High Energy Physics (CHEP)
Conference, Amsterda
Service oriented interactive media (SOIM) engines enabled by optimized resource sharing
In the same way as cloud computing, Software as a Service (SaaS) and Content Centric Networking (CCN) triggered a new class of software architectures fundamentally different from traditional desktop software, service oriented networking (SON) suggests a new class of media engine technologies, which we call Service Oriented Interactive Media (SOIM) engines. This includes a new approach for game engines and more generally interactive media engines for entertainment, training, educational and dashboard applications. Porting traditional game engines and interactive media engines to the cloud without fundamentally changing the architecture, as done frequently, can enable already various advantages of cloud computing for such kinds of applications, for example simple and transparent upgrading of content and unified user experience on all end-user devices. This paper discusses a new architecture for game engines and interactive media engines fundamentally designed for cloud and SON. Main advantages of SOIM engines are significantly higher resource efficiency, leading to a fraction of cloud hosting costs. SOIM engines achieve these benefits by multilayered data sharing, efficiently handling many input and output channels for video, audio, and 3D world synchronization, and smart user session and session slot management. Architecture and results of a prototype implementation of a SOIM engine are discussed
A Multicast Protocol for Content-Based Publish-Subscribe Systems
The publish/subscribe (or pub/sub) paradigm is a simple and easy to use model for interconnecting applications in a distributed environment. Many existing pub/sub systems are based on pre-defined subjects, and hence are able to exploit multicast technologies to provide scalability and availability. An emerging alternative to subject-based systems, known as content-based systems, allow information consumers to request events based on the content of published messages. This model is considerably more flexible than subject-based pub/sub, however it was previously not known how to efficiently multicast published messages to interested content-based subscribers within a network of broker (or router) machines. In this paper, we develop and evaluate a novel and efficient technique for multicasting within a network of brokers in a content-based subscription system, thereby showing that content-based pub/sub can be deployed in large or geographically distributed settings
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