• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.859-861
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• 2004

다중 지역으로 구성된 이동 에이전트 컴퓨팅 환경에서 결함 포용을 위한 대표적인 기법인 공간 기반 복제 기법(SRBA :Spatial-Replication-Based approach)은 이동 에이전트가 수행 중 중간 연산에 대한 빠른 결과 산출이라는 장점을 가지는 대중화된 결함 포용기법이다. 그러나 공간 기반 복제 기법을 실제 이동 에이전트 기반 컴퓨팅 환경에 적용하는데 있어서 해결되어야 하는 중요한 선결 과제 중의 하나는 단계별로 복제된 이동 에이전트들에 대한 추가 위치 관리비용을 감소시키는 것이다. 본 논문에서는 공간 기반 복제 기법에서 발생하는 불필요한 위치 관리 오버헤드를 줄이기 위해 이동에이전트를 위한 새로운 일치 관리 기법인 SRLM(Spatial Replication Location Management) 프로토콜을 제안한다. 제안된 SRLM 프로토콜은 단계군 구성시 복제된 이동 에이전트를 위한 등록 비용 및 대표 작업자에게 메시지 전달을 보강하며 메시지 전달 비용을 감소시킨다. 또한, 제안된 프로토콜은 단계 군내에서의 대표 작업자의 결함 발생시 새로운 대표 작업자의의 선출로 인한 위치 관리 문제를 해결한다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.469-471
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• 2004

다중 지역 이동 에이전트 컴퓨팅 시스템에서는 단일 지역으로 구성된 시스템에 비해서 호스트의 결함이나 호스트 사이의 통신 결함 발생 확률이 높아, 안정된 시스템 설계에 있어서 이동 에이전트의 결함을 검출하고 이를 복구하는 결함 포용 기법은 매우 중요한 고려 사항이다. 이동 에이전트의 안정적인 연산 수행을 보장하기 위한 기존의 결함 포용 기법들은 크게 시간적 복제 기반 기법(Temporal Replication Based Approach: TRBA)와 공간적 복제 기반 기법(Spatial Replication Based Approach: SRBA)으로 구분 지을 수 있으나, 다중 지역으로 구성된 이동 에이전트 시스템과 같은 복잡한 시스템에서는 낮은 결함 포용 비용이 요구되는 TRBA가 보다 적합하다. 그러나 기존의 TRBA에서는 이동 에이전트의 비멱등(non-idempotent) 연산 수행을 지원하기 위해 단일 수행 (exactly-once execution) 특성을 보장했지만, 이동 에이전트가 순환적 작업 경로를 가지는 연산 수행 시에는 작업을 완결하지 못하는 복귀월산 문제(comeback-skip problem)가 발생한다. 본 논문에서는 플래그와, 히스토리 필드, 파손 길드를 도입하여 복귀월산 문제를 해결하는 시간적 복제 기반 결함 포용 기법을 제안한다. 이 기법은 이동 에이전트의 다양한 작업 수행을 지원함으로써 이동 에이전트의 작업 수행 영역을 확대한다.

• The Journal of Korean Association of Computer Education
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• v.12 no.4
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• pp.65-75
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• 2009

The result verification is necessary to support a guarantee for the correctness of the task results be executed by any unspecified resources in desktop grid environments. Typically, voting-based and trust-based result verification schemes have been used in the environments. However, these suffer from two potential problems: waste of resources due to redundant replicas of each task and increase in turnaround time due to the inability to deal with a dynamic changeable execution environment. To overcome these problems, we propose a fuzzy inference-based replication scheme which can adaptively determine the number of replicas per task by using both trusty degree and result return probability of resources. Therefore our proposal can reduce waste of resources by determining the number of replicas meeting with a dynamic execution environment of desktop grids, not to mention an enhancement of turnaround time for entire asks. Simulation results show that our scheme is superior to other ones in terms of turnaround time, the waste of resources, and the number of re-replications per task.

• The KIPS Transactions:PartA
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• v.10A no.1
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• pp.7-14
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• 2003

In order to cope with DoS (Denial of Service) attacks disturbing delivery of intended services by exhausting resources of computing nodes, we need a solution to recognize important resources for the essential services which have to be maintained under any circumstances and to adapt the system to the urgent situation and reconfigure itself properly. In this paper, we present a two-phase scheme to handle the problem. In the first phase, by means of dynamic resource reallocation within a computing node, we try to make the selected essential services survive even after the occurrence of an attack. For the second phase when it becomes impossible to continue the service in spite of the actions taken in the first phase, we apply server replication in order to continue the transparent provision of the essential services with the end users by utilizing redundant computing nodes previously arranged. Experimental result obtained on a testbed reveals the validity of the proposed scheme. A comparison with other proposed schemes has been conducted by analyzing the performance and the cost.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.1
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• pp.30-34
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• 1997

An improved clock-feedthrough compensation scheme for switche dcurrent system is proposed. Both the signal dependent and the constant clock-feedthrough terms are cancelled by using both NMOS and PMOS current samplers and by adopting a source replication technique. The proposed current memory cell was fabricated with 0.6$\mu$m CMOS process. Both experimental and theoretical results on clock-feedthrough error reveal substantial reduction over the existing compensation schemes.

• Journal of the Korean Data and Information Science Society
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• v.20 no.6
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• pp.1177-1190
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• 2009

In this paper, we propose a fuzzy proxy cache scheme for caching web documents in mobile base stations. In this scheme, a mobile cache model is used to facilitate data caching and data replication. Using the proposed cache scheme, the individual proxy in the base station makes cache decisions based solely on its local knowledge of the global cache state so that the entire wireless proxy cache system can be effectively managed without centralized control. To improve the performance of proxy caching, the proposed cache scheme predicts the direction of movement of mobile hosts, and uses various cache methods for neighboring proxy servers according to the fuzzy-logic-based control rules based on the membership degree of the mobile host. The performance of our cache scheme is evaluated analytically in terms of average response delay and average energy cost, and is compared with that of other mobile cache schemes.

• Journal of the Korea Convergence Society
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• v.9 no.4
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• pp.9-14
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• 2018

Recently, as the internet speed is getting faster, in the cloud environment, the service receiving device is changing from a general PC to a compact device such as a mobile phone or a tablet PC. Since handheld devices such as mobile phones or tablet PCs are often used in wireless rather than wired, there are many problems that personal information may be exposed maliciously from a third party. In this paper, we propose a user privacy protection scheme through a duplicate duplicate key generation process which can safely protect user 's privacy from third party among cloud services being served through various wireless media. The proposed scheme is used to synchronize the duplicated key between the server and the intermediary device, and aims at shortening the time of the authentication process protecting the user 's privacy. In this case, the proposed scheme uses Interleave() function and random number to synchronize the server and the intermediary device, so it can safely prevent the malicious attack of the third party.

• The Journal of the Korea Contents Association
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• v.13 no.11
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• pp.21-27
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• 2013

In recently years, with the growth of social media and the development of mobile devices, the data have been significantly increased. Hadoop has been widely utilized as a typical distributed storage and processing framework. The tasks in Mapreduce based on the Hadoop distributed file system are allocated to the map as close as possible by considering the data locality. However, there are data being requested frequently according to the data analysis tasks of Mapreduce. In this paper, we propose a hot-data replication mechanism to improve the processing speed of Mapreduce according to data access patterns. The proposed scheme reduces the task processing time and improves the data locality using the replica optimization algorithm on the high access frequency of hot data. It is shown through performance evaluation that the proposed scheme outperforms the existing scheme in terms of the load of access frequency.

• The Journal of Information Technology and Database
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• v.3 no.2
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• pp.3-24
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• 1996

In this paper a data replicator scheme with a distributed join architecture is suggested with its cost functions and the performance results. The contribution of this scheme is not only minimizing the number of base relation locks in distributed database tables but also reducing the remote transmission amount remarkably, which will be able to embellish the distributed databse system practical. The differential files that are derived from the active log of the DBMS are mainly forcing the scheme to reduce the number of base relation locks. The amount of transportation between relevant sites could be curtailed by the tuple reduction procedures. Then we prescribe an algorithm of data replicator with its cost function and show the performance results compared with the semi-join scheme in their distributed environments.

• The Transactions of the Korea Information Processing Society
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• v.3 no.4
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• pp.791-802
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• 1996

In this paper, we discuss a distributed shared memory management scheme based on multi-threaded programming model for a large-scale loosely coupled multiprocessor system. The scheme covers three major issues in the distribued shared memory;the address translation table management, the block coherence maintenance, and the block placement policy. The scheme efficiently resolves the general problems occurred in the distributed shared memory such as a false sharing, an unnecessary replication, a block bouncing, and an address aliasing phenomenon. It also provides the application transparency, good scalability, easy implementation, and multithreaded programming model to users.