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A distributed attack initiated by a malicious party whose final purpose is to disrupt the services offered by a system to legitimate users is called DDoS. In recent years, many such attacks have been reported, some of them being able to cause major loses for companies or government institutions. In this paper, we analyze the impact of HOIP and Slowloris based DDoS attacks on both Windows and Linux...
In current large-scale distributed key-value stores for cloud computing, the tail latency of the hundreds of key-value accesses generated by an end-user request determines the response time of this request. Replica selection algorithms, which select the best replica server for each key-value access as much as possible, is crucial to reduce the tail latency. This paper summarizes current replica selection...
The popularity of Location-Based Services (LBSs) has resulted in varieties of applications with more conveniences in our daily life. However, since mobile users need to submit some sensitive information to the untrusted LBS servers, they may lose their privacy while they are enjoying the provided social activities. In this paper, we first point out and define the Time-Sensitive Side Information (TSSI)...
We present LAVEA, a system built for edge computing, which offloads computation tasks between clients and edge nodes, collaborates nearby edge nodes, to provide low-latency video analytics at places closer to the users. We have utilized an edge-first design to minimize the response time, and compared various task placement schemes tailed for inter-edge collaboration. Our results reveal that the client-edge...
A lack of energy proportionality, low resource utilization, and interference in virtualized infrastructure make the cloud a challenging target environment for improving energy efficiency. In this paper we present OptiBook, a system that improves energy proportionality and/or resource utilization to optimize performance and energy efficiency. OptiBook shares servers between latency-sensitive services...
Web search constitutes an important class of dataintensive online services in data centers. Optimizing search systems for energy efficiency, timely response and high search quality (i.e., how relevant the returned results are to a search query), however, is very challenging, as a search system involves a distributed architecture with hundreds of thousands of index serving nodes (ISNs) that return...
Modern distributed systems are often considered to be black boxes that greatly limit the potential to understand behaviors at the level of detail necessary to diagnose some of the most important types of performance problems. Recently researchers have found abnormal response time delays, one to two orders of magnitude longer than the average response time, that exist in short periods and cause economic...
The paper formulates methods to measure the trustsworthiness of a network system S under hostile environment conditions incident on S. How good is the system S in meeting the QoS expectations of applications (i.e. the QoS capability of S) is quantitatively measured — say on a [0,1] scale. We employ model-based assessment tools (e.g. PO-MDP) to benchmark the QoS capability by stress-testing S with...
The scalability of n-tier systems relies on effective load balancing to distribute load among the servers of the same tier. We found that load balancing mechanisms (and some policies) in servers used in typical n-tier systems (e.g., Apache and Tomcat) have issues of instability when very long response time (VLRT) requests appear due to millibottlenecks, very short bottlenecks that last only tens to...
Long-tail latency of web-facing applications continues to be a serious problem. Most of the previously published research addresses two classes of long latency problems: uneven workloads such as web search, and resource saturation in single nodes. We describe an experimental study of a third class of long tail latency problemsthat are specific to distributed systems: Cross-Tier Queue Overflow (CTQO)...
This paper presents a new aperiodic request server in real-time energy harvesting system. This server handles hard periodic tasks and soft aperiodic tasks, using ED-H in order to schedule periodic tasks. The main principle of the server is to minimize response times of aperiodic tasks without compromising the schedulability of periodic tasks. The server, known as SSP (Slack stealing with Energy Preserving),...
In multi-tier cloud service systems, performance evaluation relies on numerous experiments in order to collect key metrics such as resources usage. The approach may result in highly time-consuming in practice. In this paper, we propose an automated framework for performance tracking, data management and analysis to minimize human intervention in multi-tier cloud service systems. The framework support...
The performance of n-tier web-facing applications often suffer from response time long-tail problem. With relatively low resource utilization (less than 50%) and the majority of requests returning within a few milliseconds, a non-negligible num-ber of normally short requests may take seconds to return. We propose the millibottleneck theory of performance bugs (that lead to long-tail problems). Several...
Hybrid cloud-based deployment is a trend in cloud computing which enables enterprise to benefit from cloud infrastructures while honoring privacy restrictions on some services. Enterprise application migration is an effective way to improve the efficiency of using the cloud infrastructures. However, it is a challenging problem to decide which parts of the applications to migrate and where to migrate...
We consider a parallel-server system with K homogeneous servers where incoming tasks, arriving at rate λ, are dispatched by n dispatchers. Servers are FCFS queues and dispatchers implement a size-based policy such that the servers are equally loaded. We compare the performance of a system with n> 1 dispatchers and of a system with a single dispatcher. Every dispatcher handles a fraction 1/n of...
Fork-Join (FJ) queueing models capture the dynamics of system parallelization under synchronization constraints, for example, for applications such as MapReduce, multipath transmission and RAID systems. Arriving jobs are first split into tasks and mapped to servers for execution, such that a job can only leave the system when all of its tasks are executed. In this paper, we provide computable stochastic...
In edge-cloud computing, a set of edge servers are deployed near the mobile devices such that these devices can offload jobs to the servers with low latency. One fundamental and critical problem in edge-cloud systems is how to dispatch and schedule the jobs so that the job response time (defined as the interval between the release of a job and the arrival of the computation result at its device) is...
5G operators will utilize mobile edge computing (MEC) to shorten transmitting latency and fulfill the requirements of increasing mobile applications for high bandwidth and ultra-low latency. A mobile online system (MOS) supports mobile online applications to trigger events in the mobile devices, refresh data, and maintain data consistency in the clouds. As users run mobile online applications, a MOS...
Infrastructure-as-a-Service environments are becoming increasingly popular. When there is a failure, many applications require service restoration within a few seconds. Reaction to failures in Cloud is still slow for many applications. Monitoring is limited to instance metrics that are not conducive to precise diagnosis due to complexity of virtualization in physical hosts. Interferences among different...
Many different types of applications simultaneously execute in current data centers (DCs). To provide low cost and improved performance, each application is typically deployed in distributed DCs. Tasks of users around the world first go through Internet service providers (ISPs) which deliver data between distributed DCs and users. However, capacities and bandwidth cost of different ISPs vary. Besides,...
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