• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.118-120
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• 2004

차세대 네트워크 인프라에서 높은 대역폭을 필요로 하는 어플리케이션의 품질 보장에 대한 요구가 증가함에 따라, 네트워크의 성능을 측정하고 분석하여 특정 네트워크 지역의 병목현상이나 네트워크 장애에 대해 사전에 대비하도록 하는 장기적, 주기적으로 성능을 측정하는 인프라에 대한 필요성이 대두되고 있다. 우리는 본 논문에서, 기가급의 대역폭을 서비스를 제공하는 차세대 네트워크인 연구망의 성능을 사용자 입장에서 측정할 수 있는 인프라를 제안한다.

• Information and Communications Magazine
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• v.32 no.7
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• pp.17-26
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• 2015

최근 네트워크 기술 동향에 있어서 이른바 핫 이슈 중 하나인 소프트웨어 정의 네트워킹(SDN, Software-Defined Networking)은 바야흐로 데이터센터, 기업, 캠퍼스 등의 근거리 데이터 네트워크(LAN, Local Area Network) 환경을 넘어서 통신망 사업자(캐리어)와 서비스 제공자를 통해 원거리 데이터 네트워크 (WAN, Wide Area Network)로 진화하고 있다. 본고에서는 종단간 SDN 프로덕션 서비스를 위한 소프트웨어 정의 원거리 네트워크(SD-WAN, Software-Defined WAN)의 개요 및 적용 사례를 소개하고, SD-WAN의 핵심 서비스 기술로 인식되고 있는 네트워크 최적화, 가상화, 자동화, SDX(Software-Defined Exchange) 등의 요소 기술과 연구 동향을 알아본다.

• The Journal of the Korea Contents Association
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• v.18 no.3
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• pp.611-625
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• 2018

With innovative advances in wireless communication technology, many researches for extending network lifetime in maximum by using energy harvesting have been actively performed on the area of network resource optimization, QoS-guaranteed transmission, energy-intelligent routing and etc. As known well, it is very hard to guarantee end-to-end network delay due to uncertainty of the amount of harvested energy in multi-hop RF(radio frequency) energy harvesting wireless networks. To minimize end-to-end delay in multi-hop RF energy harvesting networks, this paper proposes an energy efficient routing metric based on interference aware and protocol which takes account of various delays caused by co-channel interference, energy harvesting time and queuing in a relay node. The proposed method maximizes end-to-end throughput by performing avoidance of packet congestion causing load unbalance, reduction of waiting time due to exhaustion of energy and restraint of delay time from co-channel interference. Finally simulation results using ns-3 simulator show that the proposed method outperforms existing methods in respect of throughput, end-to-end delay and energy consumption.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.5
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• pp.1215-1223
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• 2014

In multi-hop wireless networks, a message transmission path is set up on demand by a route discovery step, where a shortest path is used in general. The shortest path, however, normally uses the nodes near the center area, which causes a high traffic load in that area and reduces the message transmission reliability. We propose a stable routing protocol considering the remaining energy of nodes. Our protocol uses ETX as a link performance estimator and tries to avoid the nodes with smaller energy. By doing this, we can reduce the route failure probability and packet loss. We have evaluated the performance of the proposed protocol using QualNet and compared with AODV and MRFR protocols. The simulation result shows that our protocol has a similar performance as MRFR in terms of end-to-end message reception ratio, average message delay and delay jitter, but outperforms MRFR in terms of traffic load distribution.

• Journal of Satellite, Information and Communications
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• v.12 no.4
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• pp.42-49
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• 2017

Delay- and Disruption-Tolerant Network (DTN) has been considered as a key technology to overcome main challenges in interplanetary communications such as an intermittent connectivity and high bit error rates. The lack of end-to-end connectivity between source and destination results in long and variable delays and data loss, hence the Internet Protocols cannot operate properly in such environments because it requires an end-to-end connectivity. The DTN, which utilizes 'store-and-forward' message passing scheme between nodes, can overcome the lack of end-to-end connectivity in Interplanetary Network (IPN). In this paper, DTN is applied to 3-hop relay IPN, where messages are transmitted from Earth ground station to Lunar lander through Earth satellite and Lunar orbiter. ONE simulator is used to reflect the real environment of IPN and an efficient resource management method are analyzed to guarantee the message delivery by optimizing a message TTL (Time to Live), buffer size and message fragmentation.

• Convergence Security Journal
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• v.17 no.1
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• pp.53-61
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• 2017

IoT technology is evolving and related services and technologies are spreading throughout the life. These IoT technologies make life easier for users, but they also have big threats like double-edged swords. Therefore, the importance of security is emerging and related researches are actively proceeding. Existing researches have focused on reducing the computational load on the constrained devices, performing the DTLS for the end-to-end security from a network architecture perspective. In this paper, we propose a DTLS protocol that uses ECQV certificate instead of existing X.509 certificate to reduce the load of DTLS protocol from the network perspective. In addition, the proposed scheme is implemented and compared with PSK and RPK modes.

• Journal of KIISE:Information Networking
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• v.31 no.6
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• pp.608-619
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• 2004

Application layer multicast(ALM) has been developed as an alternative to support the multi-receiver applications due to the slow deployment of IP multicast. Unlike routers in IP multicast, end systems participating in a ALM session are not optimized for relaying data and have various processing and network capacity. Therefore, with the increased role of end systems, the delay incurred at the end systems occupy large portion of the end-to-end delay. In this paper, we model the end system delay of ALM sessions and analyze its impact on the performance of the existing ALM schemes. Furthermore, we propose an enhanced scheme, based on the existing mesh-based scheme, which reflects the end system delay We also evaluate the performance of the proposed scheme by simulation and show that it reduces the end-to-end delay compared with the existing scheme.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.11b
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• pp.1289-1292
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• 2003

현재 인터랙티브 서비스는 MHP와 같은 표준 스펙에서 다양하게 제안되어 시도되고 있으나, 모두 종단간 프로토콜이며, 네트워크 차원에서의 효율적인 서비스 지원을 위한 연구는 찾아보기 어렵다. 본 논문에서는 인터랙티브 서비스와 개인화 서비스를 네트워크 차원에서 지원하기 위하여, OPES 기반의 인터랙티브 방송 네트워크 구조를 제안하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.589-591
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• 2004

IP 멀티캐스트 기술은 지난 10여년동안 꾸준히 발전해 왔지만 라우터의 편재형 배치(Ubiquitous deployment)가 되지 않음으로 인해 네트워크 라우터가 패킷을 복사, 전달함으로서 종단 호스트와 네트워크 라우터 간에 부가적인 제어와 라우팅 프로토콜이 필요하게 되는 단점이 있다. 이에 대한 대안으로 현재 오버레이 네트워크를 이용한 애플리케이션 레벨 멀티캐스트가 많이 연구되고 있다. 본 논문에서는 P2P 오버레이 네트워크를 이용해 확장 (scalability)이 있고 참여지연(Join delay)이 적으면서 효율적인 트리를 구성할수 있는 애플리케이션 레벨 멀티캐스트를 제안한다.

• Journal of KIISE:Information Networking
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• v.36 no.2
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• pp.108-117
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• 2009

Data aggregation is one of the well-known techniques to reduce the energy consumption for information transmission over wireless sensor networks (WSN). As the WSNs are deployed in untrusted or even hostile environments, the data aggregation becomes problematic when end-to-end data privacy including data confidentiality and integrity between sensor nodes and base station, is required. Meanwhile, data homomorphic cryptoschemes have been investigated recently and recommended to provide the end-to-end privacy in the hostile environments. In order to assure both data confidentiality and integrity for data aggregation, this paper analyzes the existing homomorphic cryptoschemes and digital signature schemes, proposes possible combinations, and evaluates their performance in terms of CPU overheads and communication costs.