• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.243-245
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• 2004

This paper proposes design and implementation for Seamless Handoff method between adapters in a system environment where both wired and wireless adapters are present First of all, by settingLayer 2 address of wired adapter to Layer 2address of wireless adapter, then generate virtual adapter on the above layer to make these two adapters operate on an IP address. Under the condition, when wired communication via the wired adapter gets disconnected while in service, wireless handoff occurs by mapping information on the wireless adapter to the virtual adapter. According to the method proposed in this paper, continuous session can be obtained even when handoff between wired and wireless adapters occurs at lower level in an application where both IP address and Port address are used to maintain session since If address does not change.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10c
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• pp.117-119
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• 2000

UMTS(Universal Mobile Telecommunication System)의 Core Network에서는 SGSN(Serving GPRS Support Node)과 GGSN(Gateway GPRS Support Node)사이의 전송계층을 IP-Over-ATM network을 기반으로 한다. 이는 비연결형(connectionless) IP 트래픽들을 연결지향형(connectionoriented) ATM 전송계층을 통해 전송함으로 이때 효율적인 자원관리를 위해 적절한 VC(Virtual Circuit)의 접속과 해제를 수행해야 한다. 본 논문에서는 [1]에서 제안되는 GPRS(General Packer Radio Service)의 Web 트래픽 모델에 대하여 기존의 VC의 Holding-time을 결정하는 기법인 Holding Cost Pricing Model(LRU, Mean-Variance, Adaptive policy) [2]을 GGSN과 SGSN사이의 ATM 전송계층에 적용하였다. 각각의 기법들에서 VC의 이용률(utilization)과 설정율(setup rate)을 비교함으로써 Adaptive policy 기법의 성능이 다른 기법에 비해 효율적임을 알 수 있다.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.11
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• pp.1267-1276
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• 2014

As the volume of internet rapidly increases, the number of IPv4 addresses available is quickly declining, while transition to IPv6 is being delayed. As a interim solution, Variable-Length Subnet Masking(VLSM) addressing scheme, which varies the length of each IP address allowing more efficient, is being used. This paper suggests effective example of network based on virtual network with topology designed using VLSM charting rather than usual theoretical approach in VLSM, which allows more efficient use of address space.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.11b
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• pp.1189-1192
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• 2003

초기 콜 센터는 단순히 고객에게 걸려오는 전화를 응대하는 서비스 수준으로 시작되었지만, 현재는 고객과 마주하는 최 접점으로 서비스 뿐만 아니라 마켓팅, 세일즈를 행하는 기업의 경쟁력을 유지하는데 있어 필수적인 요소로 자리잡아 가고 있다. 특히 개인고객을 많이 접하는 금융기관에서는 콜 센터를 대형화, 지방 분산화 및 백업체제 구축을 위한 Multi 센터를 구축하여 콜만 처리하는 센터로서가 아니라 다양한 채널[전화,email,fax,chating]를 통해 접속되는 고객요구 사항들을 통합된 인프라에서 One Stop 으로 처리하고자 한다. 하지만 회선 교환망을 이용하는 PBX기반 Voice 회선과 IP 환경의 DATA 를 처리하는 이원화된 구조로 Multi 콜 센터를 구축 할 경우, 타 센터의 상담원에게로 콜을 설정시 시간이 많이 소요되어 센터간 Call Load Balancing 및 상담원 Skill Based Routing 을 수행함이 어렵다는 단점이 있다. 본 논문에서는 이러한 단점을 개선할 수 있는 방안으로 Voice 와 Data 를 IP 기반 단일 망으로 구성하고 WAN상에서 음성을 전달할 때 적정한 MOS(Mean opinion score)를 측정 후 객관적으로 필요한 Bandwidth 를 검증하고 Muti 콜 센터에서 효과적인 콜 load Balancing 및 Routing을 할 수 있는 VOIP기반 Convereed Virtual Call Center Architecture 설계 한다.

• Journal of International Society for Simulation Surgery
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• v.4 no.1
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• pp.17-20
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• 2017

Purpose Interactive 3D visualization system through remote data transmission over heterogeneous network is growing due to the improvement of internet based real time streaming technology. Materials and Methods The current internet's IP layer has several weaknesses against IP spoofing or IP sniffing type of network attacks since it was developed for reliable packet exchange. In order to compensate the security issues with normal IP layer, we designed a remote medical visualization system, based on Virtual Private Network. Results Particularly in hospital, if there are many surgeons that need to receive the streaming information, too much load on the gateway can results in deficit of processing power and cause the delay. Conclusion End to end security through the network method would be required.

• Journal of Communications and Networks
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• v.14 no.3
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• pp.319-335
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• 2012

In this study, we design an applicable model enabling internet protocol television (IPTV) service providers to use a virtual network (VN) for IPTV service delivery. The model addresses the guaranteed service delivery, cost effectiveness, flexible control, and scalable network infrastructure limitations of backbone or IP overlay-based content networks. There are two major challenges involved in this research: i) The design of an efficient, cost effective, and reliable virtual network topology (VNT) for IPTV service delivery and the handling of a VN allocation failure by infrastructure providers (InPs) and ii) the proper approach to reduce the cost of VNT recontruction and reallocation caused by VNT allocation failure. Therefore, in this study, we design a more reliable virtual network topology for solving a single virtual node, virtual link, or video server failure. We develop a novel optimization objective and an efficient VN construction algorithm for building the proposed topology. In addition, we address the VN allocation failure problem by proposing VNT decomposition and reconstruction algorithms. Various simulations are conducted to verify the effectiveness of the proposed VNT, as well as that of the associated construction, decomposition, and reconstruction algorithms in terms of reliability and efficiency. The simulation results are compared with the findings of existing works, and an improvement in performance is observed.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10c
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• pp.874-876
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• 2001

클러스터링(clustering)은 병렬 처리를 위한 기술로 비교적 값이 싼 컴퓨터들을 네트웍으로 연결하여 전체가 하나의 고성능 수퍼 컴퓨터처럼 동작하게 하는 기술이다. 이 클러스터 시스템의 성능을 최대한 활용하기 위해서는 디스크 입출력에 생기는 병목현상을 해결하여야 하는데, 그 해결책의 하나로 병렬파일시스템을 들 수 있다. 기존의 병렬파일시스템은 TCP/IP기반의 소켓으로 메시지를 주고받았다 그러나 TCP/IP는 프로토콜 오버헤드가 크고 처리 속도가 느리다. 본 논문에서는 이런 오버헤드를 줄이기 위해 도입된 Lightweight 메시징 기법인 VIA(Virtual Interface Architecture)를 이용하여 병렬파일시스템을 구현하기 위한 구체적인 방안을 제시하고 있다.

• Journal of KIISE:Software and Applications
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• v.36 no.6
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• pp.451-461
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• 2009

The Adaptive Random Testing(ART) aims to improve the performance of traditional Random Testing(RT) by reducing the number of test cases to find the failure region which is located in the input domain. Such enhancement can be obtained by efficient selection algorithms of test cases. The ART through Iterative Partitioning(IP-ART) is one of ART techniques and it uses an iterative input domain partitioning method to improve the performance of early-versions of ART which have significant drawbacks in computation time. And the IP-ART with Enlarged Input Domain(EIP-ART), an improved version of IP-ART, is known to make additional performance improvement with scalability by expanding to virtual test space beyond real input domain of IP-ART. The EIP-ART algorithm, however, have the drawback of heavy cost of computation time to generate test cases mainly due to the virtual input domain enlargement. For this reason, two algorithms are proposed in this paper to mitigate the computation overhead of the EIP-ART. In the experiments by simulations, the tiling technique of input domain, one of two proposed algorithms, showed significant improvements in terms of computation time and testing performance.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.7
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• pp.8-17
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• 2010

Ubiquitous home refers not only to home but also to logical space, including a wide range of out-home personal devices such as mobile phones, PDAs, laptops, car navigators, and office PCs. There are certain connection barriers among the devices, such as the dynamic IP address, NAT. In a home network, various devices coexist in heterogeneous networks, such as IP, IEEE1394, PLC, Bluetooth, ZigBee, UWB, and IrDA, all of which lack interoperability due to their different physical transmission characteristics and protocols. In ubiquitous home where an unrestricted collaboration of the devices is essential to offer services that meet the users' requirements, free interoperability among the devices must be guaranteed. This paper proposes a networking model for interoperability of the heterogeneous devices in a ubiquitous home based on a virtual overlay network which hides the complicated physical network configurations and heterogeneity of the service protocols.

• Journal of the Korea Society of Computer and Information
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• v.15 no.8
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• pp.67-78
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• 2010

Various services such as IPTV, VoIP, multimedia over IP, on-line payment, on-line game, etc. were made possible due to the rapid advance of the network. In order to provide secure and seamless services over the network, the Internet service providers are performing continuous network monitoring using NMS. The main function of NMS is to perform a diagnosis to identify the potential causes of failure from event messages. In this paper, a simulation tool, named as NetDoctor, is presented which is capable of identifying and diagnosing the potential problems in the virtual network, before the network model is constructed. In NetDoctor, a series of various and artificial failure is imposed on the virtual network, and it was analyzed if NetDoctor could identify the problems. The experimental results on virtual network show that the developed tool is very effective in identifying and diagnosing the problems. The presented simulation tool can be used in the design of robust network.