• Proceedings of the Korean Information Science Society Conference
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• 2012.06a
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• pp.305-307
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• 2012

World Wide Web (WWW)의 지속적인 성장으로 인해 Web Service의 Response Time을 수집하는 방식에 관한 연구가 진행되고 있다. 현재 Client Response Time을 수집하는 방식은 sniffer[1] 를 이용한 Agent 방식을 사용하고 있다. 하지만, 기존의 방식은 클라이언트 PC에 설치되어 수집하게 되므로 Agent의 설치가 쉽지 않고, 관리 또한 어려운 문제점을 갖고 있다. 이러한 문제점을 개선하기 위하여, 본 논문에서는 Web Application Server (WAS)[2] 에서의 Dynamic HTML 변경을 통해 Client에 추가적인 Application을 설치하지 않고도 Client의 Response Time을 Collection하는 방식에 대하여 제안하였다. 이를 통해, 사용자 (End-User)에게 추가적인 응용 프로그램을 설치하지 않고도 Dynamic HTML 을 이용하여 Client Response Time을 수집함과 동시에 Server에 Feedback할 수 있다.

• Journal of Korea Spatial Information System Society
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• v.10 no.2
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• pp.35-48
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• 2008

In this paper, we propose a Dynamic Heuristic to reduce the number of node accesses and improve quality of path in the client-based navigation service. The Dynamic Heuristic is to use heuristic data from server that is calculated with traffic data. The server-based navigation service provides a path searched on server and transmits it to client, but we propose that server only provide heuristic data to client. The proposed client searches a path with heuristic transmitted data from server. We present a new algorithm for using Dynamic Heuristic in the path-finding. The algorithm bases Grid Based Path-Finding, and has minimum speed data of edges in grid. It removes several grids whose minimum speed is less than limited speed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.394-406
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• 2004

Even the document resources offered from web server can be represented in the form of URL/URI, it can not necessarily be guaranteed that corresponding resources exist due to a dynamic change of sewer environment In this paper, integrated document administration system is therefore proposed and modeled using the XML-RPC technology which guarantees the reliance of resources, and handles a dynamic server resource management and request of clients. The proposed system is composed of middleware and server systems. The former system manages dynamic server resources, and the latter reports the updated information of documentations stored in server by client from the server to middleware system. As a result, effective storing management of dynamic resource in distributed server could be archived and building cost of a new web server could be reduced due to an applicability to current web sewer. In addition platform independent and efficient data management was obtained by using the XML-RPC protocol.

• Journal of KIISE:Computing Practices and Letters
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• v.5 no.6
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• pp.809-815
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• 1999

본 논문에서는 현재 웹의 주요한 기술로 부각되고 있는 액티브 서버페이지와 동적 웹 기술을 이용한 가상교육 시스템 구현에 대해서 다룬다. 이 시스템은 사용자로부터 프로그램 소스를 보호할 수 있고 또한 인터넷 서버에서 실행되는 액티브 서버 기술을 동적 웹 기술과 접목하여 사용자를 인지, 구별하고 사용자의 정보에 적합한 웹 페이지를 구성할 수 있다. 또한 가상교육시스템은 학년, 학과, 수강신청 정보에 따라서 적합한 사용자 환경을 구성하여 주고 수업진도에 따라 교안 및 정보를 제공할 수 있다. 이렇게 구성함으로써 시스템의 접속 사용자에 관련된 적합한 정보를 제공하여 사용자가 원하는 교육서비스를 받을 수 있게 한다.Abstract In this paper, we present our implementation of cyber education system using Dynamic Web and Active Server Pages, key technologies of the current web. This system is composed of web pages fitted to user information, which is collected and differentiated by both Active Server Technology running at server and protecting program source and Dynamic Web Technology. This system provides information and teaching content according to the progress of a course and user environments based on information such as a school year, a department and credit request information. Therefore login users can receive education services by providing adequate information related to them.

• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.544-548
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• 2004

DHCP(Dynamic Host Configuration Protocol) is a protocol which dynamically allocates an IP address and/or host configuration parameters to a host. The DHCP client's address can be changed dynamically any time. For the possible communication with other system, the DHCP client has to inform its address to the DNS system with dynamic update facility. But the DNS dynamic update has a problem related to the security. So we proposed the efficient mechanism for the secure integration of DHCP and DNS by using DNS security extensions. The system also uses the DNS server as the certificate repository for the storing & retrieval of each other's certificate.

• Journal of the Korean Data and Information Science Society
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• v.19 no.2
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• pp.645-655
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• 2008

As wireless connectivity is integrated into many handheld devices, streaming multimedia content among mobile ad-hoc peers is becoming a popular application. In this paper, we propose a dynamic service replication algorithm for providing guaranteed continuous streaming services to all nodes in mobile ad-hoc networks (MANETs). First, a MANET is comprised of logical grid hierarchy, and a streaming service is replicated to a lower server region of the logical grid hierarchy by considering the link availability between a mobile node and the streaming server within a server region or the popularity of the streaming service. We evaluate analytically the performance of the proposed algorithm, and compared with that of existing Qin's algorithm. Evaluation results show that our algorithm can achieve better streaming performance than Qin's algorithm. Therefore, the proposed algorithm not only improves the sharing availability of replicated streaming services but also controls efficiently the number of streaming service replications.

• Journal of KIISE:Information Networking
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• v.33 no.3
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• pp.231-246
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• 2006

A server load balancer is used to accept and distribute client requests to one of servers in a wireless internet proxy server cluster. LVS(Linux Virtual Server), a software based server load balancer, can support several load balancing algorithms where client requests are distributed to servers in a round robin way, in a hashing-based way or in a way to assign first to the server with the least number of its concurrent connections to LVS. An improved load balancing algorithm to consider server performance was proposed where they check upper and lower limits of concurrent connection numbers to be allowed within each maximum server performance in advance and apply the static limits to load balancing. However, they do not apply run-time server load information dynamically to load balancing. In this paper, we propose a dynamic load balancing scheme where the load balancer keeps each server CPU load information at run time and assigns a new client request first to the server with the lowest load. Using a cluster consisting of 16 PCs, we performed experiments with static content(image and HTML). Compared to the existing schemes, experimental results show performance improvement in the cases of client requests requiring CPU-intensive processing and a cluster consisting of servers with difference performance.

• KIPS Transactions on Computer and Communication Systems
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• v.2 no.7
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• pp.283-292
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• 2013

In order to ensure high performance, all the servers in an existing server cluster are always On regardless of number of real-time requests. They ensure QoS, but waste server power if some of them are idle. To save energy consumed by servers, the server power mode control was developed by shutdowning a server when a server is not needed. There are two types of server power mode control depending on when a server is actually turned off if the server is selected to be off: static or dynamic. In a static mode, the server power is actually turned off after a fixed time delay from the time of the server selection. In a dynamic mode, server power is actually turned off if all the services served in the server are done. This corresponds to a turn off after a variable time delay. The static mdoe has disadvantages. It takes much time to find an optimal shutdown time manually through repeated experiments. In this paper, we propose a dynamic shutdown method to overcome the disadvantages of static shutdown. The proposed method allows to guarantee user QoS with good power-saving because it automatically approaches an optimal shutdown time. We performed experiments using 30 PCs cluster. Experimental results show that the proposed dynamic shutdown method is almost same as the best static shutdown in terms of power saving, but better than the best static shutdown in terms of QoS.

• The KIPS Transactions:PartA
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• v.14A no.5
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• pp.269-278
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• 2007

Caching in a cache sorrel cluster environment has an advantage that minimizes the request and response tine of internet traffic and web user. Then, one of the methods that increases the hit ratio of cache is using the hash function with cooperative caching. It is keeping a fixed size of the total cache memory regardless of the number of cache servers. On the contrary, if there is no cooperative caching, the total size of cache memory increases proportional to the number of cache sowers since each cache server should keep all the cache data. The disadvantage of hashing method is that clients' requests stress a few servers in all the cache servers due to the characteristics of hashing md the overall performance of a cache server cluster depends on a few servers. In this paper, we propose the method that distributes uniformly client requests between cache servers using dynamic server information. We performed experiments using 16 PCs. Experimental results show the uniform distribution o

• Communications of the Korean Mathematical Society
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• v.24 no.1
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• pp.153-159
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• 2009

In this paper, we analyze a dynamic threshold decryption scheme proposed by Long et al. It was claimed that the scheme allows to renew the master key, or to add/remove or update a decryption server, without leaking any information on the master key and changing other decryption server's secret keys. We present an attack to Long et al's scheme by using the fact that it renews a decryption server's secret key without changing other decryption server's secret shares.