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Recent developments in the field of virtualization technologies have led to renewed interest in performance evaluation of these systems. Nowadays, maturity of virtualization technology has made a fuss of provisioning IT services to maximize profits, scalability and QoS. This pioneer solution facilitates deployment of datacenter applications and grid and Cloud computing services; however, there are challenges. It is necessary to investigate a trade-off among overall system performance and revenue and to ensure service-level agreement of submitted workloads. Although a growing body of literature has investigated virtualization overhead and virtual machines interference, there is still lack of accurate performance evaluation of virtualized systems. In this paper, we present in-depth performance measurements to evaluate a Xen-based virtualized Web server. Regarding this experimental study; we support our approach by queuing network modeling. Based on these quantitative and qualitative analyses, we present the results that are important for performance evaluation of consolidated workloads on Xen hypervisor. First, demands of both CPU intensive and disk intensive workloads on CPU and disk are independent from the submitted rate to unprivileged domain when dedicated core(s) are pinned to virtual machines. Second, request response time not only depends on processing time at unprivileged domain but also pertains to amount of flipped pages at Domain 0. Finally, results show that the proposed modeling methodology performs well to predict the QoS parameters in both para-virtualized and hardware virtual machine modes by knowing the request content size. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT Quality of service (QoS) provisioning in mobile ad hoc networks (MANETs) is one of the fundamental concerns in this area. Autonomous mobility of nodes is one of the main factors affecting the network QoS. A lack of fixed infrastructure and central control on the nodes complicate guaranteeing the QoS in MANETs. Security is a major factor affecting the QoS in such networks. This paper proposes a new routing method based on trust among the nodes and applies a clustering approach to MANETs. This routing scheme can calculate the trustworthiness of the route and the shortest routes to the destination by avoiding identified malicious nodes. The effects of node mobility and number of malicious nodes on routing performances are investigated in the reported research. Simulation is used to show the effectiveness of the proposed approach in comparison with a categorized trust method, Ad hoc On-demand Distance Vector, trust vector-based Ad hoc On-demand Distance Vector, and trust vector-based dynamic source routing in terms of end-to-end delay, network throughput, and packet delivery ratio at the expense of a moderate increase in the routing overhead. The proposed trust-based routing method finds the trustworthy route by applying end-to-end trust calculation and finds the optimal route by performing clustering scheme from the source node to the destination node. In the extended proposed routing method, adding a nonce-based encryption scheme results in improved packet delivery ratio, network throughput, and malicious node detection rate. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]