• The KIPS Transactions:PartC
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• v.15C no.4
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• pp.227-238
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• 2008

As the internet users rise up rapidly, DNS information forgery can cause severe socio-economic damages. However, most studies on DNS information security reached the breaking point in applying to actual circumstances because of the limit of existing DNS system version, the increasement of management burden and etc. The paper proposes the real-time method for detecting cache poisoning of DNS system independent of analysing the DNS forgery types in the current DNS service environment. It also proposes the method of enhancing the reliability for the cache information of Recursive DNS system by post-verifying the cache information of the DNS system.

• Journal of KIISE:Computer Systems and Theory
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• v.37 no.5
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• pp.285-291
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• 2010

Flash memory has many good features such as small size, shock-resistance, and low power consumption, but the cost of flash memory is still high to substitute for hard disk entirely. Recently, some mobile devices, such as laptops, attempt to use both flash memory and hard disk together for taking advantages of merits of them. However, existing OSs (Operating Systems) are not optimized to use the heterogeneous storage media. This paper presents a new buffer cache management scheme. First, we allocate buffer cache space according to access patterns of block references and the characteristics of storage media. Second, we prefetch data blocks selectively according to the location of them and access patterns of them. Third, we moves destaged data from buffer cache to hard disk or flash memory considering the access patterns of block references. Trace-driven simulation shows that the proposed schemes enhance the buffer cache hit ratio by up to 29.9% and reduce the total I/O elapsed time by up to 49.5%.

• Korean Management Science Review
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• v.19 no.2
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• pp.155-168
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• 2002

In this paper, some efficient implementation techniques for the multifrontal method, which can be used to compute the Cholesky factor of a symmetric positive definite matrix, are presented. In order to use the cache effect in the cache-based computer architecture, a hybrid method for factorizing a frontal matrix is considered. This hybrid method uses the column Cholesky method and the submatrix Cholesky method alternatively. Experiments show that the hybrid method speeds up the performance of the supernodal multifrontal method by 5%～10%, and it is superior to the Cholesky method in some problems with dense columns or large frontal matrices.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.4
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• pp.462-466
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• 2010

A new buffer cache management scheme that aims at reducing power consumption in mixed HDD and NAND flash memory storage systems is presented. The proposed scheme reduces power consumption by considering different energy-consumption rate of storage devices, I/O operation type (read or write), and reference potential of cached blocks in terms of both recency and frequency. Simulation shows that the proposed scheme reduces power consumption by 18.0% on average and up to 58.9%.

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.7_8
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• pp.426-433
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• 2003

Management policies of Web Proxy Cache, for the QoS of Web users, are mainly focused on the page replacement and the data consistency policy. But the two subjects have been studied independently to each other regardless of its possibility of cooperation. In this paper, we introduce the performance improvement obtained by adapting the characteristic of LMF used in data consistency policy to LRU, thus taking the better performance synergy as a result of complementary cooperation. Various policies for the management of Web Proxy Cache are in progress, this study can be a way of performance guide to increase cache hit ratio and reduce the transmission overhead of Web Server.

• Journal of Korea Multimedia Society
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• v.5 no.1
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• pp.47-56
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• 2002

Previous buffer cache schemes for multimedia storage systems only exploited the sequential references of multimedia files and didn't consider looping references. However, in some video applications like foreign language learning, users mark the scene as loop area and then application automatically playbacks the scene several times. In this paper, we propose a new buffer replacement scheme, called HBM(Hybrid Buffer Management), for multimedia storage systems that have both sequential and looping references. Proposed scheme assumes that application layer informs reference pattern of files to file system. Then HBM applies an appropriate replacement policy to each file. Our simulation experiments show that HBM outperforms previous buffer cache schemes such as DISTANCE and LRU.

• Journal of KIISE:Databases
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• v.30 no.6
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• pp.561-572
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• 2003

Broadcast-based data delivery has attracted a lot of attention as an efficient way of disseminating data to very large client populations. The main motivation of broadcast-based information systems (BBISs) is that the number of clients that they serve can grow arbitrarily large without any effect on their performance. The performance of BBISs depends mainly on client caching strategies and on data broadcast scheduling mechanisms. This paper addresses the former issue and proposes a new client cache management scheme, named 2Q-CFP, that is suitable to BBISs. This paper also evaluates the performance of 2Q-CFP on the basis of a simulation model. The performance results indicate that 2Q-CFP scheme shows superior performances over GRAY, LRU and CF in the average response time.

• Journal of Korea Society of Digital Industry and Information Management
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• v.11 no.2
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• pp.37-45
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• 2015

The technology development of MANET and dissemination of P2P services has been made very widely. In particular, the development of many application services for the integration of P2P services in MANET has been made actively. P2P networks are commonly used because of the advantages of efficient use of network bandwidth and rapid information exchange. In P2P network, the infrastructure managing each node in the middle does not exist and each node is a structure playing a role as the sender and receiver. Such a structure is very similar to the structure of the MANET. However, it is difficult to provide reliable P2P service due to the high mobility of mobile nodes. In this paper, we propose location-based routing technique in order to provide efficient file sharing and management between nodes. GMN managing the group is elected after network is configured to the area of a certain size. Each node is assigned an identifier of 12 bit dynamically to provide routing which uses location information to the identifier. ZGT is managed in the GMN in order to provide management of group nodes and distributed cache information. The distributed cache technique is applied to provide a rapid retrieval of the sharing files in the each node. The excellent performance of the proposed technique was confirmed through experiments.

• The KIPS Transactions:PartD
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• v.10D no.6
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• pp.961-970
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• 2003

In data broadcasting environments, the server periodically broadcasts data items in the broadcast channel. When each client wants to access any data item, it should monitor the broadcast channel and wait for the desired item to arrive. Client data caching is a very effective technique for reducing the time spent waiting for the desired item to be broadcastted. This paper proposes a new client cache management scheme, named LRU-CFP, to reduce this waiting time ans evaluates its performance on the basis of a simulation model. The performance results indicate that LRU-CFP scheme shows superior performance over LRU, GRAY and CF in the average response time.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.394-396
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• 2004

CE 제품에 리얼타임 OS를 도입하면서, 제품의 조건을 만족시키기 위한 기술에 대해 많은 연구가 진행되고 있다. 특히, CE 제품에 있어서 중요한 이슈인 부팅 시간은 펌웨어수준과 비교했을 때 코드사이즈나 OS 초기화 과정 때문에 다소 느려지는 경향을 보이고 있다. 본 논문은 이러한 CE 제품의 부팅 시간에 초점을 맞추고 리얼타임 OS 적용시의 부팅 시간을 개선하였다. 구현에 사용된 ARM920T Core는 32-비트 RISC 구조이며, 각 16KB의 인스트럭션 Cache와 데이터 Cache, 그리고 MMU(Memory Management Unit)로 구성되어 있으며, 리얼타임 OS는 선점형 방식의 커널로 구성된 OS를 사용하였다.