• Journal of the Korea Computer Industry Society
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• v.6 no.3
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• pp.391-400
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• 2005

최근 몇 년 사이 컴퓨터와 초고속 통신망의 대중적인 보급으로 인하여 인터넷 사용 인구가 급격하게 증가하였고 인터넷 사용량 또한 폭발적으로 증가하였다. 이와 같이 막대한 양으로 늘어난 트래픽은 서버에 과도한 양의 부하를 발생시켜 서비스 전반에 걸친 성능 저하를 가져왔다. 따라서 서버에 많은 양의 트래픽이 발생하더라도 정상적인 서비스를 제공할 수 있도록 하는 것이 필요하다. 본 논문에서는 이러한 서버의 트래픽 폭주로 인한 서버 과부하 문제를 해결하기 위해 수락 제어 알고리즘을 이용한다. 수락 제어 기법은 컨텐츠 변환이나 로드 밸런싱과 같이 수동적으로 부하를 덜어주거나 분산시키는 방식이 아닌 트래픽에 제한을 가하여 능동적으로 서버의 부하를 조절하는 방식이다. 클라이언트에 의한 연결 요청이 이루어질 때 서버의 부하 상태를 평가한 후 서버가 수용 가능한 수준이면 클라이언트 새로운 연결 요청을 수락하여 이를 서비스할 수 있도록 한다. <중략> 또한 서비스 요청에 제한적인 정책을 따를 경우 서버의 부하 변화에 빠르게 반응하지만 QoS(Quality of Service)의 향상을 얻을 수 있는 반면 더 많은 서비스 요청을 수용하는 정책을 취할 경우 서버의 부하 변화에 대한 반응이 느리지만 throughput이 증가하는 이득을 얻을 수 있게 된다. QoS와 throughput가 서로 tradeoff 관계에 있다는 것을 알 수 있다. 또한 요구되는 서비스의 성격에 따라 즉 더 높은 수준의 QoS 보장이 중요한 서비스인가 아니면 더 높은 수준의 throughput 보장이 요구되는 서비스인가에 따라 다른 수락 제어 정책을 적용하는 것이 가능하게 된다.

• The Journal of the Korea Contents Association
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• v.11 no.3
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• pp.26-35
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• 2011

In these days, internet environment are very quickly development as well on-line service have been using a online for the mission critical business around the world. As the amount of information to be processed by computers has recently been increased there has been cluster computing systems developed by connecting workstations server using high speed networks for high availability. but cluster computing technology are limited for a lot of IT resources. So, grid computing is an expanded technology of distributed computing technology to use low-cost and high-performance computing power in various fields. Although the purpose of Grid computing focuses on large-scale resource sharing, innovative applications, and in some case, high-performance orientation, it has been used as conventional distributed computing environment like clustered computer until now because grid middleware does not have common sharable information system. In order to use grid computing environment efficiently which consists of various grid middleware, it is necessary to have application-independent information system which can share information description and services, and expand them easily. This paper proposed new database architecture and load balancing for high availability through Grid technology.

• Journal of KIISE
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• v.44 no.1
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• pp.13-20
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• 2017

A message processor is server software that receives various message formats from clients, creates the corresponding threads to process them, and lastly delivers the results to the destination. Considering that each function of an SEDA-based message processor has its own characteristics such as CPU-bound or IO-bound, this paper proposes a thread-mapping strategy called "FC-TM" (function-characteristic aware thread mapping) that schedules the threads to the cores based on the function characteristics in multi-core environments. This paper assumes that message-processor functions are static in the sense that they are pre-defined when the message processor is built; therefore, we profile each function in advance and map each thread to a core using the information in order to maximize the throughput. The benchmarking results show that the throughput increased by up to a maximum of 72 % compared with the previous studies when the ratio of the IO-bound functions to the CPU-bound functions exceeds a certain percentage.

• The KIPS Transactions:PartC
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• v.12C no.4 s.100
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• pp.543-550
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• 2005

Many routing algorithms, proposed for ad-hoc wireless networks, we based on source routing scheme and shortest path route has short lifetime especially in highly dense ad-hoc wireless networks. So some routing protocols such as SSA and ABR are considering the link stability and try finding more stable route. In this paper we propose a new routing algorithm considering utilization metric based on SSA routing algerian in Ad-Hoc networks. To reduce the bottleneck by specific metric of SSA, proposed scheme makes load balancing in networks by distributing the connections to several routes. For the evaluation of the performance we compare our scheme with existent routing protocol AODV and SSA. And the results, obtained using the ns-2 network simulation platform, show good performance that reduced the number of reconstructions remarkably by distributing the whole traffic to several routes when there are several stable routes.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.11a
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• pp.201-204
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• 2003

At a consequence of WWW large popularity, the internet has suffered from various performance problems, such as network congestion and overloaded servers. These days, it is not uncommon to find servers refusing connections because they are overloaded. Web server performance has always been a key issue in the design and operation of on-line systems. With regard to Internet, performance is also critical, because users want fast and easy access to all objects (e.g., documents, graphics, audio, and video) available on the net. To solve this problem, a number of companies are exploring the benefits of having multiple geographically or locally distributed Internet sites. This requires a comprehensive scheme for traffic management, which includes the principle of an optimal load balancing of client requests across multiple clusters of real servers. This paper focuses on the performance analysis of Web server and we apply these results to load balancing in clustering web server. It also discusses the mam steps needed to carry out a WWW performance analysis effort and shows relations between the workload characteristics and system resource usage. Also, we will introduce an optimal load balancing algorithm base on the RTSM (Real-Time Server Monitor) and Fuzzy Inference Engine for the local status of a real server, and the benefits is provided with of the suggested method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12B
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• pp.818-830
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• 2005

Recently, Peer-to-Peer (P2P) overlay networks like CAN, Chord, Pastry and Tapestry offer a novel platform for scalable and decentralized distributed applications. These systems provide efficient and fault-tolerant routing, object location, and load balancing within a self-organizing overlay network. Content Delivery Network (CDN) is an intermediate layer of infrastructure that helps to efficiently deliver the multimedia content from content providers to clients. In this paper, We propose a topology-aware P2P overlay network for CDN, Rosary, in which CDN servers perform Intra-Pastry and Inter-Pastry routing based on a two-level structured overlay network. This proposed system extends pastry by adapting itself to CDN environments, where a semi-hashing based scheme for Intra-Pastry routing is introduced, and dynamic landmark technology is used to construct the topology-aware overlay network. Through simulations on NS-2, it is shown that Rosary is scalable, efficient, and flexible.

• Journal of KIISE:Information Networking
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• v.41 no.4
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• pp.177-185
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• 2014

It has been occurred many times that wireless sensor networks (WSNs) had congested areas because all the sensing data collected by multiple sensor nodes are delivered to one sink node. Typically, in order to control congested areas, it used to reduce the traffic by increasing the sensing period or discarding packets. However, those schemes have a disadvantage that it loses the reliability when delivering sensing data. Moreover, there are no schemes considering case of having poor quality of links between nodes in practical terms. In this paper, we suggest a scheme not to reduce the traffic but to distribute the traffic by changing routing paths depends on the traffic and the quality of links. Also, it can be seen that the reliability of delivering of the sensing data is improved with the experiments improving collection rates and shortening end-to-end delay.

• Journal of KIISE
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• v.42 no.1
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• pp.15-22
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• 2015

In this paper, we present a case study for a drug repositioning simulation based on distributed supercomputing technology that requires highly efficient processing of large-scale computations. Drug repositioning is the application of known drugs and compounds to new indications (i.e., new diseases), and this process requires efficient processing of a large number of docking tasks with relatively short per-task execution times. This mechanism shows the main characteristics of a Many-Task Computing (MTC) application, and as a representative case of MTC applications, we have applied a drug repositioning simulation in our HTCaaS system which can leverage distributed supercomputing infrastructure, and show that efficient task dispatching, dynamic resource allocation and load balancing, reliability, and seamless integration of multiple computing resources are crucial to support these challenging scientific applications.

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.7_8
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• pp.352-358
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• 2003

A cluster of servers is the most promising solution to provide highly scalable and highly available network services with low implementation cost. One of popular solutions is using dispatcher as a request distributor. However this solution has the problem that is can be the bottleneck or single-point of failure point of itself. ONE-IP, the previous work, solves this serious problem by using broadcast message for distributing the request packet in LAN. Using simple scheduling technique, in addition, the overhead due to dispatching the request becomes minimal. However, as ONE-IP using very simple static scheduling algorithm, it would spread the request among servers unevenly and downgrades the cluster performance consequently. In this paper, we propose an improved TCP connection scheduling technique solving this unbalanced distributing problem. Using Round-Robin(RR) scheduling instead of hashing clients IP address, proposed technique can more evenly distribute incoming service requests among the servers. Experiments show average 3.8% improved performance in throughput compared to original ONE-IP technique.

• KIPS Transactions on Computer and Communication Systems
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• v.10 no.12
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• pp.311-318
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• 2021

With the rapid development of the Internet of Things(IoT) technology recently, multi-access edge computing(MEC) is emerged as a next-generation technology for real-time and high-performance services. High mobility of users between MECs with limited service areas is considered one of the issues in the MEC environment. In this paper, we consider a vehicle edge computing(VEC) environment which has a high mobility, and propose a task migration algorithm to decide whether or not to migrate and where to migrate using DQN, as a reinforcement learning method. The objective of the proposed algorithm is to improve the system throughput while satisfying QoS(Quality of Service) requirements by minimizing the difference between queueing delays in vehicle edge computing servers(VECSs). The results show that compared to other algorithms, the proposed algorithm achieves approximately 14-49% better QoS satisfaction and approximately 14-38% lower service blocking rate.