• Journal of Communications and Networks
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• 제11권3호
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• pp.306-317
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• 2009

We consider the problem of architecting a reliable content delivery system across an overlay network using TCP connections as the transport primitive. We first argue that natural designs based on store-and-forward principles that tightly couple TCP connections at intermediate end-systems impose fundamental performance limitations, such as dragging down all transfer rates in the system to the rate of the slowest receiver. In contrast, the ROMA architecture we propose incorporates the use of loosely coupled TCP connections together with fast forward error correction techniques to deliver a scalable solution that better accommodates a set of heterogeneous receivers. The methods we develop establish chains of TCP connections, whose expected performance we analyze through equation-based methods. We validate our analytical findings and evaluate the performance of our ROMA architecture using a prototype implementation via extensive Internet experimentation across the PlanetLab distributed testbed.

• 한국정보과학회논문지:정보통신
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• 제33권4호
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• pp.289-298
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• 2006

응용 계층 멀티캐스트에서 일반적으로 트리를 구성하여 데이타를 전송하는데, 이 경우 트리 상에서 하위 (descendants) 노드들이 체감하는 처리율 (throughput)은 상위 (ancestor) 노드들의 성능에 의해 좌우된다. 그리고, 상위 노드에서 오류가 하위 노드 전체에 영향을 끼친다는 단점을 갖는다. 본 문서에서는 이러한 트리 구조의 약점들을 보완하는 방법을 제안한다. 전송 트리 상의 부모 노드 외의 다수의 가상 소스를 설정하고, 이들로부터 데이타를 수신함으로써 단위 시간 수신량을 늘리며 부모 노드의 오류를 피해갈 수 있는 방안을 마련한다. 그리고, 다수의 가상 소스를 이용할 경우 발생할 수 있는 통일 데이타의 중복 수신 문제를 피할 수 있도록 가상 소스 선택 알고리즘을 제시한다. 응용 계층 멀티캐스트 시험 개발 환경인 MACEDON을 이용하여 시험 구현하였고, 이를 전세계적인 오버레이 네트워크 PlanetLab에 적용하여 성능 평가를 시행하였다. 성능 평가 결과, 기존의 다수 전달자를 제안하는 기법인 Bullet에 비하여 20% 성능을 향상시키면서 동시에 중복 수신되는 데이타 및 제어에 필요한 메시지 비용을 90% 이상 감소시키는 효과를 볼 수 있었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권1호
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• pp.22-37
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• 2013

Content distribution to a large number of concurrent clients stresses both server and network. While the server limitation can be circumvented by deploying server clusters, the network limitation is far less easy to cope with, due to the difficulty in measuring and balancing network load. In this paper, we use two useful network load metrics, the worst link stress (WLS) and the degree of interference (DOI), and formulate the problem as partitioning the clients into disjoint subsets subject to the server capacity constraint so that the WLS and the DOI are reduced for each session and also well balanced across the sessions. We present a network load-aware partition algorithm, which is practicable and effective in achieving the design goals. Through experiments on PlanetLab, we show that the proposed scheme has the remarkable advantages over existing schemes in reducing and balancing the network load. We expect the algorithm and performance metrics can be easily applied to various Internet applications, such as media streaming, multicast group member selection.

• 한국멀티미디어학회논문지
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• 제19권2호
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• pp.428-435
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• 2016

Hundreds of millions of new posts and information are being uploaded and propagated everyday on Online Social Networks(OSN) like Twitter, Facebook, or Instagram. This paper proposes and implements a GPS-location based SNS data mapping, analysis, and visualization system, called Smart SNS Map, which collects SNS data from Twitter and Instagram using hundreds of PlanetLab nodes distributed across the globe. Like no other previous systems, our system uniquely supports a variety of functions, including GPS-location based mapping of collected tweets and Instagram photos, keyword-based tweet or photo searching, real-time heat-map visualization of tweets and instagram photos, sentiment analysis, word cloud visualization, etc. Overall, a system like this, admittedly still in a prototype phase though, is expected to serve a role as a sort of social weather station sooner or later, which will help people understand what are happening around the SNS users, systems, society, and how they feel about them, as well as how they change over time and/or space.

• 대한인간공학회지
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• 제31권1호
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• pp.7-13
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• 2012

Objective: This paper discussed the characteristics of service design process by comparing with product design process. Background: Service design has different design outcomes, project participants, and design constraints than product design. Method: The comparison took two perspectives: one was shorter-term, design process of a service, and the other was longer-term, process of service development. Results: It was discussed that service design process is similar in overall, but has four differences. First, the role of design is required earlier and longer in the process, which means service designers need to participate from the begging of the project to service operation. Thus service designers are required to have holistic viewpoint of the project. Second, service design requires many design expertise thus collaboration needs to be well defined and managed throughout the process. Third, since service provider has limited resources, regulations, and market competition, some service features cannot be provided. Service designers are required to know both customers' needs and functional constraints. Last, service design is highly coupled with service operation. Designing and providing service happens at the same time and evolves over time. Conclusion: Consequently it was asserted that the role of designers in service design is essential for success. In specific, the role of service design architect, who manages design process and design outcomes, is a new and important role in service design project.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권1호
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• pp.133-151
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• 2019

In order to achieve faster content distribution speed and stronger fault tolerance, a P2P peer can connect to multiple peers in parallel and receive chunks of the data simultaneously. A critical issue in this environment is selecting a set of nodes participating in swarming sessions. Previous related researches only focus on performance metrics, such as downloading time or the round-trip time, but in this paper, we consider a new performance metric which is closely related to the network and propose a peer selection algorithm that produces the set of peers generating optimal worst link stress. We prove that the optimal algorithm is practicable and has the advantages with the experiments on PlanetLab. The algorithm optimizes the congestion level of the bottleneck link. It means the algorithm can maximize the affordable throughput. Second, the network load is well balanced. A balanced network improves the utilization of resources and leads to the fast content distribution. We also notice that if every client follows our algorithm in selecting peers, the probability is high that all sessions could benefit. We expect that the algorithm in this paper can be used complementary to existing methods to derive new and valuable insights in peer-to-peer networking.

• 한국항행학회논문지
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• 제20권4호
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• pp.275-284
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• 2016

항공기 배기가스가 지구의 현재와 미래의 기후에 미치는 잠재적 영향력은 항공산업계가 당면하고 있는 매우 중요한 환경 이슈 중 하나이다. 온실가스 배출의 잠재적 악영향에 대한 우려가 증가함에 따라 기후에 관한 항공기의 영향을 완화하는 수단 중 하나로 항공기 배기가스를 산정하고 예측할 필요성이 제기되고 있다. 따라서 본 연구에서는 항공기 배기가스의 산출과 저감효과 분석을 통한 항공기 온실가스 배출량을 최소화하여 미래 기후변화와 에너지 고갈에 대비하는 것을 연구목표로 한다. 우선 민간 항공 교통 스케줄을 보유한 OAG 데이터를 사용하여 우리나라 공항에 대한 항공 비행 일정을 확보하였다. 이후 미국 MIT 대학 항공 환경 실험실에서 개발한 AEIC 소프트웨어를 사용하여 2005년 한해 동안 우리나라 모든 공항에서의 3,000 ft 이하의 고도에서 이륙, 상승, 접근, 착륙단계를 포함하는 LTO 운항 시와 3,000 ft 이상의 고도에서 상승, 순항, 하강단계를 포함하는 non-LTO 운항 시의 연료소모량과 온실가스 배출량을 계산하여 결과 데이터를 각 조건별로 비교분석하였다.

• 디지털융복합연구
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• 제18권12호
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• pp.279-284
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• 2020

2020년 1월, COVID19는 온 지구를 팬데믹에 빠트렸다. 이로 인해 경제적으로 큰 손실을 가져왔으며, 사회적으로 혼란을 일으키고 있다. 이러한 코로나19는 심장병, 고혈압, 당뇨, 뇌졸중, 우울증, 암 등과 같은 기저질환자들에게 감염률이 월등히 높다. 또한, 기저질환자가 기저질환이 없는 사람들보다 치명률이 훨씬 높다고 연구되었다. 본 연구에서는 뇌파데이터를 이용하여 기저질환의 유·무를 분류하였다. 기저질환자 유·무에 대한 분류를 위해 사용된 데이터는 데이터사이언스랩에서 제공하는 뇌파데이터로 33개의 특징과 69개의 샘플로 이루어졌다. 데이터의 전처리는 Z-score를 사용하였다. 분류는 뉴럴네트워크 인 NEWFM와 ZNN엔진을 사용하였다. 실험 결과 기저질환자의 유·무에 대한 분류결과 NEWFM은 77.94%, ZNN은 76.47%의 실험 결과를 얻었다. 이 연구를 통해 뇌파데이터를 측정하고 기저질환의 유무를 분류하고 높은 감염률을 보이는 기저질환자들이 COVID19로부터 예방 할 수 있으리라 기대한다. 이를 기반으로 향후 기저질환에 대한 세분류를 할 수 있는 연구가 필요하고, 각 기저질환이 전염병에 미치는 영향에 대해서도 연구가 필요하다.

• International Journal of Computer Science & Network Security
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• 제21권11호
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• pp.345-353
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• 2021

Cloud computing represent a new era of computing that's forms through the combination of service-oriented architecture (SOA), Internet and grid computing with virtualization technology. Virtualization is a concept through which every cloud is enable to provide on-demand services to the users. Most IT service provider adopt cloud based services for their users to meet the high demand of computation, as it is most flexible, reliable and scalable technology. Energy based performance tradeoff become the main challenge in cloud computing, as its acceptance and popularity increases day by day. Cloud data centers required a huge amount of power supply to the virtualization of servers for maintain on- demand high computing. High power demand increase the energy cost of service providers as well as it also harm the environment through the emission of CO₂. An optimization of cloud computing based on energy-performance tradeoff is required to obtain the balance between energy saving and QoS (quality of services) policies of cloud. A study about power usage of resources in cloud data centers based on workload assign to them, says that an idle server consume near about 50% of its peak utilization power [1]. Therefore, more number of underutilized servers in any cloud data center is responsible to reduce the energy performance tradeoff. To handle this issue, a lots of research proposed as energy efficient algorithms for minimize the consumption of energy and also maintain the SLA (service level agreement) at a satisfactory level. VM (virtual machine) consolidation is one such technique that ensured about the balance of energy based SLA. In the scope of this paper, we explore reinforcement with fuzzy logic (RFL) for VM consolidation to achieve energy based SLA. In this proposed RFL based active VM consolidation, the primary objective is to manage physical server (PS) nodes in order to avoid over-utilized and under-utilized, and to optimize the placement of VMs. A dynamic threshold (based on RFL) is proposed for over-utilized PS detection. For over-utilized PS, a VM selection policy based on fuzzy logic is proposed, which selects VM for migration to maintain the balance of SLA. Additionally, it incorporate VM placement policy through categorization of non-overutilized servers as- balanced, under-utilized and critical. CloudSim toolkit is used to simulate the proposed work on real-world work load traces of CoMon Project define by PlanetLab. Simulation results shows that the proposed policies is most energy efficient compared to others in terms of reduction in both electricity usage and SLA violation.