• Proceedings of the Korean Information Science Society Conference
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• 2011.06a
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• pp.391-394
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• 2011

3rd party content service is a consumer-based wide selection of contents in which IPTV provider believes will enhance the service considerably extending the variety of contents to finally provide a personalized service. Therefore, the combination of 3rd party content services and the IPTV infrastructure creates a good revenue opportunity but they need to be created. IPTV offers to create personalized channels to distribute 3rd party content service. However, the cost of $3^{rd}$ party content delivery is high when the service is provided from a faraway server. IPTV provider requires an effective strategy of replica placement to minimize the cost without a tradeoff on the performance. We propose a cluster-based strategy of replica placement to find the right balance between cost and performance. The results demonstrate the achievement of an outstanding delivery time and low cost.

• ETRI Journal
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• v.26 no.4
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• pp.360-366
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• 2004

Synchronization Markup Language (SyncML) is a specification of a common data synchronization framework for synchronizing data on networked devices. SyncML is designed for use between mobile devices that are intermittently connected to a network and network services that are continuously available on the network. We have designed and developed a data synchronization system based on the SyncML protocol and evaluated the throughput of the system using the stochastic Petri nets package (SPNP) and analyzed the relationship between the arrival rate and the system resources. Using this model, we evaluate various performance measures in different situations, and we estimate the relationship between the arrival rate and the system resources. From the results, we can estimate the optimal amount of resources due to the arrival rate before deploying the developed system.

• IEMEK Journal of Embedded Systems and Applications
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• v.8 no.3
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• pp.145-153
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• 2013

Virtualization technology has been applied in IA-32 based server or desktop systems. Recently it has been applied in ARM based mobile systems. Virtualization technology provides many useful features that are not possible in operating system level such as isolation, interposition, encapsulation and portability. In this research, we implement an ARM based VMM(Virtual Machine Monitor) by using the following techniques. First, we use "emulation" to virtualize the processor. Second, we use "shadow page tables" to virtualize the memory. Finally, we use a simple "pass-through I/O" to virtualize the device. Currently the VMM runs ARM Linux kernel 3.4.4 on a BeagleBoard-xM, and we evaluated the performance of the VMM using lmbench and dhrystone. The result of the evaluation shows that our VMM is slower than Xen on ARM that is implemented using paravirtualization but has good performance among the VMMs using full-virtualization.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.12
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• pp.3121-3131
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• 1996

In this papre we implemented the ISDN S-interface Card for a PABX that makes it possible to accommodate ISDN terminals. In order to implement this ISDN cand we first designed entire structure and functions of its hardware and software. And then based on this we implemented server and entity, inter-entity communication, ISDN protocols, and call processing interface for realizing ISDN interface functions. Finally we evaluated the performance of the implemented ISDN card by measuring the response time of call setup and release.

• Journal of Ocean Engineering and Technology
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• v.24 no.4
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• pp.66-71
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• 2010

Numerical prediction of propeller performance plays an important role in a marine propeller design process. Program developers are consistently trying to improve diminish predicted errors, and program users need to keep up with the latest ones with minimum expenditure of time and money. We have developed an internet based design system in which clients can design propellers with remote access. In this paper, optimized Internet based Propeller Design and Analysis System (iProDAS) for transferences of the massive data is presented, and a sample design using iProDAS is examined.

• Journal of the Korea Society for Simulation
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• v.14 no.4
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• pp.31-41
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• 2005

This paper proposes a novel Web Services enhancement method, which enhances XML based e-commerce and Web Services securely and efficiently. Recently, the ratio of XML Denial of Services (XDOS) is increased significantly However, XML data is visible only at the target application site or the application layer. Thus, an efficient and secure mechanism handling XML data on the network layer to provide fast performance on the server and protect XDOS at network level is strongly required basic component. This paper presents many issues and gives useful results from the various experiments to support an implemented XAN platform.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.1
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• pp.497-522
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• 2018

Fully homomorphic encryption(FHE) scheme may be the best method to solve the privacy leakage problem in the untrusted servers because of its ciphertext calculability. However, the existing FHE schemes are still not being put into the practical applications due to their low efficiency. Therefore, it is imperative to find a more efficient FHE scheme or to optimize the existing FHE schemes so that they can be put into the practical applications. In this paper, we optimize GSW scheme by using the parallel computing, and finally we get a high-performance FHE scheme, namely PGSW scheme. Experimental results show that the time overhead of the homomorphic operations in new FHE scheme will be reduced manyfold with the increasing of processing units number. Therefore, our scheme can greatly reduce the running time of homomorphic operations and improve the performance of FHE scheme through sacrificing hardware resources. It can be seen that our FHE scheme can catalyze the development of FHE.

• Annual Conference of KIPS
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• 2005.11a
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• pp.1499-1502
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• 2005

본 논문에서는 차별화 서비스(Differentiated Service)를 구현하기 위하여 퍼지 이론을 적용한 웹 서버 컴퓨팅 노드들의 동적인 성능 분리(Performance Isolation) 기법에 관하여 논하였다. 제안된 기법은 컴퓨팅 노드의 현재 부하량, 사용자 계층별 요청률을 퍼지 입력 변수(Fuzzy Variables)로 하여, 애매모호한 노드의 정량적 부하를 정성적으로 표현할 수 있도록 하였으며, 이를 통해 계층별 요청률의 급격한 변화에 대응하여, 계층별 요청을 처리하는 담당 노드의 수를 동적으로 조절할 수 있게 하였다. 성능분석을 통해 제안된 퍼지 기반 성능 분리 방식의 서비스 응답시간이 퍼지기법을 사용하지 않은 일반적인 성능 분리에 비해 개선되는 것을 확인하였다.

• Journal of Communications and Networks
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• v.5 no.3
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• pp.240-248
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• 2003

This paper analyzes mobile agent performance in network management compared to the client-server model used in the Simple Network Management Protocol (SNMP). Prototypes of an application that gathers MIB-II (Management Information Base-II) variables have been created and tested on a LAN. After acquiring implementation parameters related to network management and to the mobile agent infrastructure, simulation results have been obtained on large topologies similar in shape to the Internet. Response time results show that mobile agents perform better than SNMP when the number of managed elements ranges between two specific limits, an inferior bound and a superior one, determined by the number of messages that pass through a backbone and by the mobile agent size which grows along with MIB-II variables collected on network elements. The results also show that a significant improvement is achieved when the mobile agent returns or sends data to the management station after visiting a fixed number of nodes.

• Journal of the Korea Society for Simulation
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• v.13 no.3
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• pp.1-10
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• 2004

The cell loss probability required in the ATM network is in the range of 10$^{-9}$ ∼10$^{-12}$ . If Monte Carlo simulation is used to analyze the performance of the ATM node, an enormous amount of computer time is required. To obtain large speed-up factors, importance sampling may be used. Since the Markov-modulated processes have been used to model various high-speed network traffic sources, we consider discrete time single server queueing systems with Markov-modulated arrival processes which can be used to model an ATM node. We apply importance sampling based on the Large Deviation Theory for the performance evaluation of, MMBP/D/1/K, ∑MMBP/D/1/K, and two stage tandem queueing networks with Markov-modulated arrival processes and deterministic service times. The simulation results show that the buffer overflow probabilities obtained by the importance sampling are very close to those obtained by the Monte Carlo simulation and the computer time can be reduced drastically.