• Journal of Broadcast Engineering
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• v.25 no.1
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• pp.94-104
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• 2020

Currently media consumption over fixed/mobile Internet is mostly conducted by adaptive media streaming technology such as DASH (Dynamic Adaptive Streaming over HTTP), which is an ISO/IEC MPEG (Moving Picture Experts Group) standard, or some other technologies similar to DASH. All these heavily depend on the HTTP caches that ISPs (Internet Service Providers) are obliged to provide sufficiently to make sure fast enough Web services. As a result, as the number of media streaming users increases, ISPs' burden for HTTP cache has been greatly increased rather than CDN (Content Delivery Network) providers' server burden. Hence ISPs charge traffic cost to CDN providers to compensate for the increased cost of HTTP caches. Recently in order to reduce the traffic cost of CDN providers, P2P (Peer-to-Peer)-assisted DASH system was proposed and a peer selection algorithm that maximally reduces CDN provides' traffic cost was investigated for this system. This algorithm, however, tends to concentrate the burden upon the selected peer. This paper proposes a new peer selection algorithm that distributes the burden among multiple peers while maintaining the proper reduction level of the CDN providers' cost. Through implementation of the new algorithm in a Web-based media streaming system using WebRTC (Web Real-Time Communication) standard APIs, it demonstrates its effectiveness with experimental results.

• Journal of Internet Computing and Services
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• v.6 no.2
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• pp.69-84
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• 2005

As the Internet users are increasing rapidly, a cluster web server system is attracted by many researchers and Internet service providers. The cluster web server has been developed to efficiently support a larger number of users as well as to provide high scalable and available system. In order to provide the high performance in the cluster web server, efficient load distribution is important, and recently many content-aware request distribution techniques have been proposed. In this paper, we propose a new content-aware load balancing technique that can evenly distribute the workload to each node in the cluster web server. The proposed technique is based on the hash histogram transformation, in which each URL entry of the web log file is hashed, and the access frequency and file size are accumulated as a histogram. Each user request is assigned into a node by mapping of (hashed value-server node) in the histogram transformation. In the proposed technique, the histogram is updated periodically and then the even distribution of user requests can be maintained continuously. In addition to the load balancing, our technique can exploit the cache effect to improve the performance. The simulation results show that the performance of our technique is quite better than that of the traditional round-robin method and we can improve the performance more than $10\%$ compared with the existing workload-aware load balancing(WARD) method.

• The KIPS Transactions:PartA
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• v.9A no.3
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• pp.327-332
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• 2002

Conventional proxy web cache, which is generally used to caching server, is a content-copy based system. This method focuses on speeding up the phase delivery not improving the webserver performance. However, if immense clients attempt to connect the webserver simultaneously, the proxy web cache cannot achieve the desired result. In this paper, we propose the web accelerator called the SCALA-AX, whitch improves web server performance by accelerating the delivery contents. The SCALA-AX is built in the Linux-based kernel as a kernel modulo and works in combination with the conventional webserver program. The SCALA-AX speeds up the processing rate of the webserver, because it processes the requests using the kernel thread. The SCALA-AX also applies the well-developed cache algorithm to the processing, and thus it obtains the advantage of the caching server without installing additional hardware. A banchmarking test demonstrates that the SCALA-AX improves webserver performance by up to 500％ for content delivery.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06a
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• pp.218-220
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• 2012

인터넷 활용과 웹 어플리케이션의 개발이 증가함에 따라 처리해야하는 데이터의 양도 또한 증가하고 있다. 대량의 데이터를 효과적으로 처리하기 위한 방법 중 하나로 병렬처리 프로그래밍 모델인 맵리듀스가 있다. 하둡은 맵리듀스의 오픈소스 구현으로 대량의 데이터를 병렬로 처리하는 무료 자바 소프트웨어 프레임워크이다. 분산 파일 시스템을 사용하는 하둡에서는 처리하는 데이터가 다른 노드에 위치하는 데이터 로컬리티 문제가 전체 작업 수행시간의 증가를 야기하는 문제가 있다. 본 논문에서는 하둡에서의 데이터 로컬리티 문제를 해결하기 위한 데이터 복제기법을 제안한다. 제안하는 데이터 복제기법에서는 1) 라그랑지 보간법을 사용하여 과거 접근수를 이용한 미래 접근수를 예측하고, 2) 예측된 값을 Threshold값으로 설정하고, 3) 데이터 로컬리티 문제가 발생하였을 때, 복제사본을 생성할 것인지 캐시를 생성할 것인지를 결정하여 복제 사본의 수를 최적화 한다. 실험을 통해 단순히 복제사본 수를 증가시킴으로써 데이터 로컬리티를 향상을 이루어도 작업 완료시간이 감소하는 것이 아니라는 결과를 볼 수 있었고, 오버 런치로 인한 작업 완료시간 증가를 줄이기 위해 데이터 복제사본 수 최적화의 필요성을 확인할 수 있었다.

• Journal of the Korea Society of Computer and Information
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• v.10 no.5 s.37
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• pp.217-226
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• 2005

In today's cyberworld, network performance is affected not only by an increased demand for legitimate content request, but also by an increase in malicious activity. In this Paper, we research that network performance was affected by an increase in malicious Hacker who make DoS Attack, DDoS Attack, SYN Flooding, IP Spoofing, etc. in using TCP/IP. We suggest that Packet filtering in Network Level, Gateway Level, Application Level against to Protect by Hacker's attack. Also, we suggest that content distribution in Web Server approaches to mitigate Hacker's activity using Cache Sever, Mirror Sever, CDN. These suggests are going to use useful Protection methode of Hacker's attack.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.2
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• pp.319-324
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• 2011

Recently, development of app for smartphone is much and many apps provide information by reproduced with achieved information from internet site. There is a need of method dependent on reproduced data by app. For solving these requirements, this paper first identifies problems such as lower hardware performance and limited bandwidth when legacy web pages are accessed by smart phones. This paper suggests three methods, "real time," "cache," and "static" to develop application programs for smart phones by considering identified problems.

• Journal of the Korea Society of Computer and Information
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• v.29 no.7
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• pp.109-115
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• 2024

Overleaf is a cloud-based LaTeX editor, allowing users to easily create and collaborate on documents without the need for separate LaTeX installation or configuration. Thanks to this convenience, users from various fields worldwide are writing, editing, and collaborating on academic papers, reports, and more via web browsers. However, the caching that occurs during the process of converting documents written on Overleaf to PDF format poses risks of exposing sensitive information. This could potentially lead to the exposure of users' work to others, necessitating the implementation of security measures and vigilance to caution against such incidents. This paper delves into an in-depth analysis of Overleaf's security vulnerabilities and proposes various measures to enhance the protection of intellectual property.

• The KIPS Transactions:PartD
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• v.14D no.4 s.114
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• pp.447-458
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• 2007

The objective of this study is to provide faster mobile web service by improving performance of Contents Cache used for mobile web service in the existing Mobile Gate System. It was found that two elements existed in Mark-Up page transcoded by Contents Generator. One of the elements was dependent only on the requested DIDL page and Mark-Up type. The other was dependent on each of the requested DIDL page, Mark-Up type, size of mobile display 모바일 장치 to request service, type of images available and color depth count of the images available. The conventional Contents Cache saved the entire Mark-Up page to hold both of the two elements. This caused the problem where storage space was not effectively used because reusable elements were repetitively saved in cache memory domain due to change in one of the elements even though all the other elements were the same. As a result, a larger number of transcoded Mark-Up pages could not be saved in the same cache memory size. Therefore, in this study, Mark-Up pages transcoded by Contents Generator were divided into two elements and were separately saved. Also, in order to respond to the demand for replacing data in cache with new data, this study applied two algorithms of LFU and LRU. This study proposed the method to implement cache performance of faster speed by enabling to save more number of the transcoded Mark-Up pages in the same cache storage space.

• Journal of KIISE:Databases
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• v.37 no.6
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• pp.308-314
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• 2010

As the price of flash memory continues to drop and the technology of flash SSD controller innovates, high performance flash SSDs with affordable prices flourish in the storage market. Nevertheless, it is hard to expect that flash SSDs will replace harddisks completely as database storage. Instead, the approach to use flash SSD as a cache for harddisks would be more practical, and, in fact, several hybrid storage architectures for flash memory and harddisk have been suggested in the literature. In this paper, we propose a new approach to use flash SSD as an extended buffer for main buffer in database systems, which stores the pages replaced out from main buffer and returns the pages which are re-referenced in the upper buffer layer, improving the system performance drastically. In contrast to the existing approaches to use flash SSD as a cache in the lower storage layer, our approach, which uses flash SSD as an extended buffer in the upper host, can provide fast random read speed for the warm pages which are being replaced out from the limited main buffer. In fact, for all the pages which are missing from the main buffer in a real TPC-C trace, the hit ratio in the extended buffer could be more than 60%, and this supports our conjecture that our simple extended buffer approach could be very effective as a cache. In terms of performance/price, our extended buffer architecture outperforms two other alternative approaches with the same cost, 1) large main buffer and 2) more harddisks.

• Journal of Korea Spatial Information System Society
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• v.11 no.1
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• pp.55-62
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• 2009

In u-GIS environment, we collect spatial data needed through sensor network and provide them with information real-time processed or stored. When information through Internet is requested on Web based applications, it is transmitted in XML. Especially, when requested information includes spatial data, GML, S-XML, and other document that can process spatial data are used. In this processing, real-time stream data processed in DSMS is transformed to S-XML document type and spatial information service based on web receive S-XML document through Internet. Because most of spatial application service use existing spatial DBMS as a storage system, The data used in S-XML and SDBMS needs transformation between themselves. In this paper, we propose S-XML a transformation method using caching of spatial data. The proposed method caches the spatial data part of S-XML to transform S-XML and relational spatial database for providing spatial data efficiently and it transforms cached data without additional transformation cost when a transformation between data in the same region is required. Through proposed method, we show that it reduced the cost of transformation between S-XML documents and spatial information services based on web to provide spatial information in u-GIS environment and increased the performance of query processing through performance evaluation.