• The KIPS Transactions:PartA
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• v.12A no.5 s.95
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• pp.375-384
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• 2005

General purpose operating systems are Increasingly being used for serving time-sensitive applications. These applications require soft real-time characteristics from the kernel and from other system-level services. In this paper, we explore various operating systems techniques needed to support time-sensitive applications and describe the design of MUSMA(Multi-level Scheduler for Multimedia Application). MUSMA is a framework that combination of user-level top scheduler and kernel-level bottom scheduler. We develope MUSMA in linux environment and it's performance is evaluated. Experiment result shows that it is possible to satisfy the constraints of multimedia in a general purpose operating system without significantly compromising the performance of non-realtime applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8B
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• pp.755-761
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• 2004

Currently, Wireless LAN(WLAN) service is widely deployed to provide high speed wireless Internet access through the mobile stations such as notebook and PDA. To provide enhanced security and user access control in the public WLAN area, WLAM access points should have the capability of IEEE 802.1x-based user authentication and authorization functionality. In this paper, we provide a brief understanding of IEEE 802. 1x standards and related protocols likeEAPoL(Extended Authentication Protocol Over LAN), EAP, RADIUS and describe how the IEEE 802.1x is designed and implemented in our embedded linux-based WLAN AP which is named i-WiNG.(Intelligent Wireless Internet Gateway).

• Journal of Internet Computing and Services
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• v.3 no.2
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• pp.27-37
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• 2002

This paper analyzes problems of existing Mobile IP and redesigns component functions, and proposes handover method using LRS and BCS for handover performance improvement. When mobile node moves another domain, the proposed BCS recognizes its mobility. So, BCS manages mobile node's binding information and serves micro mobility. When handover occurs among domains, micro mobility enables using LRS, As BCS and LRS have buffering function, they can reduce packet loss by forwarding the buffered datagram. It's designed component is implemented in LINUX environment. And then, handover performance was evaluated by simulation. The results of proposed handover method are better than existing method in both transmission delay time and packet loss.

• Journal of KIISE:Computing Practices and Letters
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• v.7 no.6
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• pp.703-714
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• 2001

In C language, a local buffer overflow in stack can destroy control information stored near the buffer. In case the buffer overflow is used maliciously to overwrite the stored return address, the system is exposed to serious security vulnerabilities. This paper analyzes the process of buffer overflow hacking and methodologies to avoid the attacks in details. And it proposes a device of static buffer overflow detection by using function summary and tracking information flow of buffer domain at assembly source code level(SASS, Static Assembly Source code Scanner) and then show the feasibility and validity of it by implementing a prototype in Pentium based Linux environment.

• Journal of KIISE:Information Networking
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• v.28 no.1
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• pp.22-36
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• 2001

WWW의 급격한 발전은 몇몇 웹 서버에 큰 과부하를 가져오게 하였다. 이로 인해 고성능 웹서버의 구축이 필요하게 되었는데 그중 프로세스의 오버헤드를 줄이기 위해 도입된 멀티 쓰레드 기법을 이용한 병행 웹 서버들이 많이 이용되게 되었다. 일반적으로 멀티 쓰레드 기법을 이용하는 웹 서버의 구조는 요구 기반 웹 서버 작업 기반 웹 서버 Thread Pool 구조 웹 서버 등으로 나눌수 있다. 본 논문에서는 이런 웹 서버들을 리눅스가 탑재되어 있는 다중 처리기상에 구현하였으며 다양한 환경하에서 성능을 비교 분석하였다 각각의 웹 서버들은 Pthread 라이브러리와 Socket 라이브러리를 이용하여 구현하였으며 여러 파라미터-CPU 개수 CGI 비율, 웹 서버구조, 파일크기 부하량 등-를 조절하면서 실험하였다 실험 결과 분석에 의하면 요구 기반 웹 서버에서는 하나의 CPU에서 수행이 되는 쓰레드의 개수가 많게 되면 성능이 저하되는 것을 볼 수 있었고 작업 기반 웹 서버에서는 단계사이의 불균형으로 인하여 큐에서의 대기 시간이 누적되면 성능이 저하되는 것을 볼수 있었다,. Thread Pool 구조의 웹서버는 쓰레드의 개수가 조절되고 큐에서의 대기 시간 또한 없앰으로 해서 다른 웹 서버에 비해 좋은 성능을 보임을 알 수 있었다. 이와 같은 실험 결과는 다중 처리기를 이용한 고성능 웹 서버를 구축하는데 있어서 이용될 수 있을 것이다.

• The KIPS Transactions:PartA
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• v.10A no.4
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• pp.305-312
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• 2003

In the embedded Linux environments, developers can concurrently debug multiple processes that have parent-child relationships using multiple gdbs and gdbservers. But, it needs additional coding efforts and messy works of activating another gdbs and gdbservers for each created process, and so, it may be inefficient in the viewpoint of developers. In this paper, we propose a mgdb library and mgdbserver that supports concurrent debugging of multiple processes in the embedded Linux systems by using the library wrapping mechanism without modifying the kernel. Also, through the experimentation of concurrent debugging for multiple processes that communicate by an unnamed pipe, we show that our proposed debugging mechanism is more efficient than the preexisting mechanisms.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.04a
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• pp.653-656
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• 2002

본 연구는 데이터웨어하우징/의사결정시스템, 그리고 업무 처리 자동화 소류션등 새로운 애플리케이션 개발로 이하여 발생하는 엄청난 양의 데이터를 효율적으로 관리하기 위한 백업 서장 시스템을 SAN 환경을 지원하는 SANtopia 파일시스템에서 동작하도록 설계 구현하였다. 지금까지 데이터 저장시스템은 하나의 서버에 접속되어 있어서 네트워크 상의 다른 컴퓨터가 직접 활용하는 것을 허용하지 않기 때문에 기존의 네트웍을 기반으로 하는 파일서버 형태로는 이러한 대용량의 자료를 저장하고 관리하는데 한계가 있다. 이러한 문제를 해결할 수 있는 방법으로 Fibre Channel과 LAN 네트워크 모델을 결합하여 대역폭(Bandwidth)의 병목 현상을 크게 완화할 수 있는 SCSI 명령어를 이용하여 SANtopia 파일 시스템에서 파티션별 Full backup과 Restore 할 수 있는 시스템을 리눅스 기반에서 구현하였다.

• Journal of Korea Society of Industrial Information Systems
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• v.20 no.6
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• pp.11-20
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• 2015

This paper describes design and implementation experience of SAS-G2S slotmachine accounting protocol middleware system that converts the legacy binary format SAS (Slot Accounting System) protocol with servers with recent standards G2S protocol. The paper examines the difference of two protocols such as link control, message format, and parameters. The converter architecture uses bridge and connector patterns and implemented in C++ and Python mixed language on Linux environment. The prototype system uses a 1GMHz-512MB linux machine and has passed Korean official protocol compatibility and performance test in 2015.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9B
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• pp.818-825
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• 2004

High availability means Service-technology that can provide any solution when occur a problem in relation to hardware, software, network etc. We are in the times that the network computing service are essential to our daily life. So the importance of the high availability is being higher and higher in this social change such as the arrival of information anger times, e-commerce the extension of multi-media service etc. In this thesis, I analyzed about High-availability Linux Server for Multimedia Tourism Information System, and I proposed an alternative plan which related with its result.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.8
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• pp.1762-1767
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• 2005

PKI provides good resolutions for the authentication of user in the situation not to meet each other, but it is not enough to provide the resolution of authorization in distributed computing environments. Especially, we offer a variety forms of the user Authentication, the Integrity and a security service of the Non-Repudiation, but an authorization Policy, because of the complexity with a lot of information, using m understandable XML, makes a simple and easy certificate to read, and we get the information from DOM fee and do a XML analysis and stardardized-method usage easily In this paper, we provide the AAS model being able to use with the solution of the distributed users' authorization, and we implement an authorization policy module, using XML. in the Linux-based Apache Web server.