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Network Function Virtualization (NFV) enables mobile operators to virtualize their network entities as Virtualized Network Functions (VNFs), offering fine-grained on-demand network capabilities. VNFs can be dynamically scale-in/out to meet the performance desire and other dynamic behaviors. However, designing the auto-scaling algorithm for desired characteristics with low operation cost and low latency,...
We explore the impact of using different modeling paradigms on the outcome of simulation studies. Modeling paradigms, once implemented, follow different computational rules regarding how calculations are made and are sequenced during runtime. To test the effects of computational differences on a simulation's outcomes, we implement a simple queuing system as a Discrete Event Simulation model, a System...
In cloud computing paradigm, virtual resource autoscaling approaches have been intensively studied recent years. Those approaches dynamically scale in/out virtual resources to adjust system performance for saving operation cost. However, designing the autoscaling algorithm for desired performance with limited budget, while considering the existing capacity of legacy network equipment, is not a trivial...
The tutorial will be used to introduce some basic techniques for analysing the output of stochastic simulation models. Using examples, we will describe methods for determining the optimal warm-up length and number of replications as well as introducing ways of using simulation to compare different systems.
One of the most critical and costly decisions made in emergency departments (EDs) is whether to admit a patient into the hospital. These decisions require investment in time for patient testing and treatment, delaying care to other patients. Short-stay units (SSUs) are an alternative to discharging or fully admitting ED patients, allowing extended patient observation. However, little is understood...
In situ processing proposes to reduce storage needs and I/O traffic by processing results of parallel simulations as soon as they are available in the memory of the compute processes. We focus here on computing in situ statistics on the results of N simulations from a parametric study. The classical approach consists in running various instances of the same simulation with different values of input...
Cloud Data Centers (CDC) are developing rapidly and will have a major impact on IT infrastructures in the future for reasons of their low ramp-up costs and service delivery/support capabilities for the users. In this paper CDCs with multi-service application classes are considered which are operated under an automatic server consolidation based on parallel hysteresis methods for server activations/deactivations...
Mobile phones are more and more used for sensitive resources exchange and access, becoming target for possible malware attacks. These attacks are still increasing with the birth of new and sophisticated malware that make the existing malware detection approaches often inadequate. Since the majority of new malware are generated using existing malicious code, it becomes very important tracking the mobile...
As the amount of mobile traffic carried over IP keeps increasing, the military networks face the scalability challenges of VoIP protocols. When the message arrival rate including retransmissions exceeds the message serving capacity of a Session Initiation Protocol (SIP) server, the queue size increases and eventually the SIP server can be crashed. In our previous studies, we proposed a priority based...
Stored procedures in database management systems are often used to implement complex business logic. Correctness of these procedures is critical for correct working of the system. However, testing them remains difficult due to many possible states of data and database constraints. This leads to mostly manual testing. Newer tools offer automated execution for unit testing of stored procedures but the...
Evaluating security threat status is very important in network security management and analysis. Aquantitative hierarchical threat evaluation model is developed in this paper to evaluate security threat status of a computer network system and the computational method is developed based on the structure of the network and the importance of services and hosts. The evaluation policy from bottom to top...
An analysis of the familiarity between users in a group requires large amounts of information. We could determine the degree of familiarity by using personal information gleaned from a social networking service. For a realtime service, we usually use video data. Unfortunately, this data is closely related to a user's privacy, so the user may feel uncomfortable about its use. Therefore, in this study,...
Computer networks consist of several assets such as hardware, software, and data sources. These assets have often some vulnerabilities which can be exploited by attackers that violate security policies in the network. Considering the limited budget, the network administrator should analyze and prioritize these vulnerabilities to be able to efficiently protect a network by mitigating the most risky...
In this paper, we contribute to modeling and analyzing the end-to-end (E2E) packet transmission in the cache-enabled networks, where the wired backhaul and the radio access network (RAN) are jointly considered. The performance of the on-peak system is first considered with modeling the two-dimensional queue process in terms of the queue length and the time. The cumulative distribution function (CDF)...
Wi-Fi is a cost-effective way to offload the increasing data traffic from cellular networks. However, users can only associate to one access point (AP) at a time, which limits the offloading performance in multiple hotspots scenario. In order to enhance the offloading performance and improve the utilization of Wi-Fi capacity as well, we propose a terminal-to-terminal (T2T) communication incorporated...
climateprediction.net has traditionally been an activity that requires a large amount of computing resources from its volunteer network, whilst allowing a time-frame of weeks to months for simulations to be returned for each project. However, there is an increasing trend of projects requiring results in shorter and shorter timescales. Under no project is this clearer than in the World Weather Attribution...
Federated environment consists of multiple domains, traditional cross domain authentication model has many defects like weak cross domain ability, overload of authentication server, cookie hidden danger and non-cross domain limitation. The paper analyzes the security risks of the current authentication model, then we propose a cross domain federal identity authentication model, which adopts the multi-agent...
Virtual switches are a key elements within the new paradigms of Software Defined Networking (SDN) and Network Function Virtualization (NFV). Unlike proprietary networking appliances, virtual switches come with a high level of flexibility in the management of their physical resources such as the number of CPU cores, their allocation to the switching function, and the capacities of the RX queues, which...
Data with vastly different access characteristics is efficiently stored in multi-tiered storage systems. A cost-effective way to retain large volumes of infrequently accessed data is to store it on tape. Steady developments in tape technology deliver ever increasing storage capacities at low cost. This has established tape as a viable solution to cope with the extreme data growth in the context of...
In this paper, we study the dynamics of coupled speed scaling systems, in which service rate is a function of system occupancy. We focus on both Processor Sharing (PS) and Shortest Remaining Processing Time (SRPT) as scheduling disciplines, and study their speed scaling dynamics under heavy load. Using a combination of Markov chain analysis and discrete-event simulation, we identify several important...
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