• Journal of KIISE:Information Networking
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• v.28 no.3
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• pp.435-446
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• 2001

In this paper, a new fairness control method is proposed to distribute DQDB-SR (Distributed-Queue Dual-Bus with Slot Reuse) network bandwidth fairly to all stations on client-server environments. By using an access limit that follows a characteristic of client-sever load patterns and a bandwidth borrowing and returning mechanism, the proposed mechanism imparts fairness bandwidth control capability to DQDB-SR. To implement the proposed mechanism, we find the optimal placement of erasure nodes that maximizes network capacity for DQDB-SR, and calculate the access limit. At overload conditions, simulation results show that the proposed mechanism does not deteriorate network throughput, and outperforms other fairness control mechanisms in a success rate and an average packet transfer delay.

• The KIPS Transactions:PartB
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• v.9B no.5
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• pp.555-562
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• 2002

Increasing of electronic commerce users and high-capacity multimedia data is the main causes of increasing of load and network traffic in electronic commerce system. Increasing of load and network traffic brings the delay of service about client's request. And it's becoming factor that decreases customer satisfaction and corporation's competitive ability. So it is needed to research that consider efficient management and response time of electronic commerce system. In this paper, we designed electronic commerce system based on local server with web cashing function in order to solve load problem of electronic commerce system. And we proposed web cashing algorithm for local web server and analyzed performance by an experiment.

• Journal of Korea Multimedia Society
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• v.12 no.3
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• pp.345-353
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• 2009

It is for sure that a stable game managing system is absolutely needed to accept simultaneous interfacing of many users for P2P on-line game system. The proposed P2P on-line game system in this paper is able to get smart and stable game managing taking care of extensive players through reorganizing numerous RS(Region Server) and mutual communications among RS's which can be avoid congestion on one region. Moreover, it is possible to synchronize for game nodes in time stamp utilizing Global Zone Buffer of Monitoring Server which leads to breakup loads. The system manages middleware layers in the so-called sub area, and it is able to execute no matter how big the game sizes are. That means, in some ways, we got everything we try to ensure such as the problems of high cost server and stabilization of message transmission. This paper welcomes to prove efficiency of the suggested system through the simulation.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10d
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• pp.202-204
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• 2002

네트워크에서 사용되는 정보들은 수많은 패킷으로 구성되어 송수신 되는데 이러한 패킷의 정보를 이용하여 많은 정보를 알아낼 수 있다. 패킷의 정보를 통계적으로 분석해 외부로부터의 침입과 정보의 유출을 방지할 수 있으며 네트워크의 문제점을 파악하여 시스템을 안전하게 관리 할 수 있다. 그리고 각종 프로토콜을 분석해 네트워크의 부하와 사용자의 행위 패턴과 요구사항을 알아낼 수 있다. 그러나 사용자로부터 실시간으로 들어오는 패킷을 하나의 서버가 처리하고 분석하는 경우에는 많은 부하가 생긴다. 본 연구에서는 실시간으로 생성되는 패킷 데이터를 효율적으로 처리하고 분석하는데 있어서 분산 시스템을 이용하여 해결 하고자 한다. 사용자로부터 생성되는 패킷을 IP그룹별로 분리하여 각각의 프로토콜별로 저장하고 처리하는 부하균형을 이룬 패킷 마이닝 분산 시스템을 제안하고자 한다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.6
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• pp.97-106
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• 2003

The important factor in Public-Key Infrastructure is the authentication to correspondent. We receive the digital certificate for authentication between each other, and then we check the existence of validity on the certificate by Certification Revocation List(CRL). But, To use CRL is the scheme used in offline status. So, it is impossible to refer to the latest information and the CRL scheme which is used after downloading is variously unsuitable to getting bigger of the CRL size as time goes on. Therefore, we prefer OCSP(Online Certificate Status Protocol) used in online to CRL used in offline. Consequently, we propose the scheme which provides the request of fast verification in case of requesting the verification on the certificate by owning the same update information to Certificate Registry and distributed OCSP.

• Journal of IKEEE
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• v.7 no.2 s.13
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• pp.265-270
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• 2003

We divide networks of an organization into internal network and external network to distribute the load of web server, and allocate separate web server for each network. The performance of web server for internal networks can be affected seriously by RTO(Retransmission Timeout). The value of RTO set by default in the OS of an web server is so large that it degrades the performance of web server. Therefore, this paper suggests not useing but applying conventional algorithm to calculate RTO, but to apply newly controlled value of RTO, and it showed improvement of the performance of web server.

• The KIPS Transactions:PartD
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• v.13D no.6 s.109
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• pp.839-846
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• 2006

Context-aware adaptive service for overcoming the limitations of wireless devices and maintaining adequate service levels in changing environments is becoming an important issue. However, most existing studies concentrate on an adaptation module on the client, proxy, or server. These existing studies thus suffer from the problem of having the workload concentrated on a single system when the number of users increases md, and as a result, increases the response time to a user's request. Therefore, in this paper the adaptation module is dispersed and arranged over the client, proxy, and server. The module monitors the contort of the system and creates a proposition as to the dispersed adaptation system in which the most adequate system for conducting operations. Through this method faster adaptation work will be made possible even when the numbers of users increase, and more stable system operation is made possible as the workload is divided. In order to evaluate the proposed system, a prototype is constructed and dispersed operations are tested using multimedia based learning content, simulating server overload and compared the response times and system stability with the existing server based adaptation method. The effectiveness of the system is confirmed through this results.

• The Transactions of the Korea Information Processing Society
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• v.4 no.8
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• pp.2092-2105
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• 1997

In this paper, we propose a load sharing scheme in distributed systems. In the proposed scheme, the state of each host is classified as a server or a source by its current load and, to prevent excessive state changes of each host, we used three threshold values for identifying the current state of each host. Based on the threshold values, some hosts, called brokers, manage the servers registered to them. The brokers, whose number is determined by the system utilization factor and the total number of hosts, support task migration processes from overloaded sources to lightly loaded servers. Also they can hand over the broker's role to another host when it is overloaded. Simulation studies were performed for examining the sensitivity of each system parameters such as threshold values, utilization factor, the number of hosts, and the number of brokers to the system performance indices including mean response time, mean queue length.

• Proceedings of the Korea Multimedia Society Conference
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• 2002.05c
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• pp.58-63
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• 2002

본 논문에서는 분산 환경을 위해 OMG에서 발표한 CORBA의 표준에 따라 하는 컴파일러의 전반부를 위해 OMG IDL 컴파일러를 사용하였다. CORBA에서 클라이언트와 서버간의 상호 동작을 위해 인터페이스를 정의한다. CORBA에서 인터페이스는 IDL(Interface Definition Language)를 통해 정의를 할 수 있다. IDL은 CORBA의 인터페이스를 기술하기 위한 추상 표기법이므로 개발에 사용되는 언어와는 연관성이 없다. 이를 개발에 사용하기 위해서 해당 언어로 맵핑을 하여야 한다. 본 논문은 IDL로 정의된 인터페이스를 C++로 맵핑하도록 하여 분산 객체 환경을 지원하도록 하기 위한 것이다. IDL 컴파일러는 IDL 정의를 입력 받아 어휘 및 구문 분석을 한 후 AST 트리를 생성하며, 생성된 각 노드를 통해 맵핑된 C++ 코드를 생성토록 한다.

• Journal of KIISE:Computing Practices and Letters
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• v.6 no.4
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• pp.441-447
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• 2000

In this paper, we design and implement an Internet GIS based on ObjectWeb, which makes to use various distributed services and object paradigm. We use CORBA, which is the standard of distributed object middleware and supports interoperability and reusability regardless of the execution environment and the implementation language of a distributed code, so that it easily extends established systems in networking environment and accesses distributed heterogeneous spatial data. Our method distributes parts of user interactive tasks to clients to reduce and to improve the system performance while existing approaches concentrate all workloads on a server. We implement a travel information system on the developed IGIS. Users receive services from remote servers employing a Java client system running on a web browser.