• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.3
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• pp.414-416
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• 2013

As the usage of the electric power train increases, the importance of the control network between the electric control devices grows. IEC proposed a revision of IEC-61375, a standard of the networking among electric devices within a train, to adopt Ethernet as a backbone of train network. This paper performed the reliability analysis of three configurations of Ethernet-based networking within a electric power train that are recommended in IEC-61375 standard. The analysis results show that MTTF(mean time to failure) of the redundant configuration is 20,086 hours, which is a about 3 times longer than the linear configuration.

• Journal of Communications and Networks
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• v.7 no.1
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• pp.1-12
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• 2005

Ethernet is being deployed in metropolitan area networks (MANs) as a lower-cost alternative to SONET-based infrastructures. MANs are usually required to support common communication services, such as voice and frame relay, based on legacy synchronous TDM technology in addition to asynchronous packet data transport. This paper addresses the clock synchronization problem that arises when transporting synchronous services over an asynchronous packet infrastructure, such as Ethernet. A novel algorithm for clock synchronization is presented combining time-stamp methods used in the network time protocol (NTP) with signal processing techniques applied to measured packet interarrival times. The algorithm achieves the frequency accuracy, stability, low drift, holdover performance, and rapid convergence required for viable emulation of TDM circuit services over Ethernet.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04d
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• pp.605-607
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• 2003

파장 다중 분할 Ethernet PON(Passive Optical Network)은 최근 들어 활발하게 연구되고 있는 경제적이고 효율적인 가입자망 구조이다. 가입자망의 구조가 다양하게 진화하고 광 이더넷 기술이 발전하면서 가입자에게 최적의 대역폭을 할당하기 위해 파장 다중 분할 Ethernet PON에서도 서비스별 대역폭 할당방식을 제공해야 할 필요성이 커지고 있다. 따라서, 본 논문에서는 사용자의 대역폭 요구에 따라 OLT(Optical Line Termination)가 각 ONU(Optical Network Unit)에게 서로 다른 방식으로 대역폭을 할당하는 과장 다중 분할 Ethernet PON 모델을 제시하고 구현한다. 그리고, ONU의 큐잉 지연과 단대단 Etherent 지연에 대한 분석을 통해 모델의 효율성을 제시한다.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04d
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• pp.608-610
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• 2003

Ethernet PON(Passive Optical Network)에서 핵심 기술 중의 하나인 MAC(Media Access Control) 프로토콜은 ONU(Optical Network틴nit)들이 상향으로 트래픽을 전송할 때 공유되어 있는 링크상의 충돌을 방지하고, 효율적인 대역폭을 할당하기 위한 스케줄링 알고리즘을 포함하고 있다. 본 논문에서는 차세대 가입자 망인 Ethernet PON에서 상향으로의 대역폭 부족을 개선하기 위하여, n개의 파장을 사용한 가변 슬롯 할당 TDMA(Time Division Multiple Access) 방식의 MAC 프로토콜을 제안한다. 이를 검증하기 위하여 OPNET 시뮬레이션 도구를 이용해 Ethernet PON 모델을 설계하고 시뮬레이션 한다.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.3
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• pp.389-395
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• 2013

Ethernet is the most widely deployed access network protocol around the world. IEEE 802.3az WG released the EEE standard based on LPI mode to improve the energy efficiency of Ethernet. This paper proposes improved adaptive power control mechanism that can enhance energy-efficiency based on EEE from small Ethernet switch. The feature of this mechanism is that it predicts the traffic characteristic of next cycle by measuring the amount of traffic flowing in during certain period and adjusts the optimal threshold value to relevant traffic load. Performance evaluation results indicate that the proposed mechanism improves overall performance compared to traditional mechanism, since it significantly reduces energy consumption rate, even though average packet delay increases a little bit.

• ETRI Journal
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• v.34 no.6
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• pp.816-826
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• 2012

Self-healing Ethernet rings show promise for realizing the SONET/SDH-grade resilience in Carrier Ethernet infrastructures. However, when a ring is faulty, high-priority protection messages are processed in less time than low-priority data frames are processed. In this situation, any delayed data frames either being queued or traveling through long ring spans will cause the ring nodes to generate incorrect forwarding information. As a result, the data frames spread in the wrong direction, causing the ring to become unstable. To solve this problem, we propose four schemes, that is, dual flush, flush delay timer setting, purge triggering, and priority setting, and evaluate their protection performance under various traffic conditions on a ring based on the Ethernet ring protection (ERP) method. In addition, we develop an absorbing Markov chain model of the ERP protocol to observe how traffic congestion can impact the protection performance of the proposed priority setting scheme. Based on our observations, we propose a more reliable priority setting scheme, which guarantees faultless protection, even in a congested ring.

• ETRI Journal
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• v.32 no.2
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• pp.184-194
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• 2010

Ethernet ring protection (ERP) technology, which is defined in ITU-T Recommendation G.8032, has been developed to provide carrier grade recovery for Ethernet ring networks. However, the filtering database (FDB) flush method adopted in the current ERP standard has the drawback of introducing a large amount of transient traffic overshoot caused by flooded Ethernet frames right after protection switching. This traffic overshooting is especially critical when a ring provides services to a large number of clients. According to our experimental results, the traditional FDB flush requires a link capacity about sixteen times greater than the steady state traffic bandwidth. This paper introduces four flush optimization schemes to resolve this issue and investigates how the proposed schemes deal with the transient traffic overshoot on a multi-ring network under failure conditions. With a network simulator, we evaluate the performance of the proposed schemes and compare them to the conventional FDB flush scheme. Among the proposed methods, the extended FDB advertisement method shows the fastest and most stable protection switching performance.

• Journal of Energy Engineering
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• v.14 no.2 s.42
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• pp.112-116
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• 2005

This paper describes the implementation of DCS communication network that provides high bandwidth and reliability. The network for DCS in this paper adopts the Reflective Memory (RM) architecture and Fast Ethernet physical media that have 100 Mbps bandwidth. Also, This network uses Ring Enhancement Device (RED) which is invented to reduce the time delay of each node. The DCS network that is introduced in this paper is named as ERCNet (Ethernet based Real-time Control Network). This paper describes the architecture and working algorithms of ERCNet and performs numerical analysis. In addition, the performance of ERCNet is evaluated by experiment using the developed ERCNet network.

• ETRI Journal
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• v.27 no.4
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• pp.355-366
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• 2005

Automatic discovery of physical topology plays a crucial role in enhancing the manageability of modern metro Ethernet networks. Despite the importance of the problem, earlier research and commercial network management tools have typically concentrated on either discovering logical topology, or proprietary solutions targeting specific product families. Recent works have demonstrated that network topology can be determined using the standard simple network management protocol (SNMP) management information base (MIB), but these algorithms depend on address forwarding table (AFT) entries and can find only spanning tree paths in an Ethernet mesh network. A previous work by Breibart et al. requires that AFT entries be complete; however, that can be a risky assumption in a realistic Ethernet mesh network. In this paper, we have proposed a new physical topology discovery algorithm which works without complete knowledge of AFT entries. Our algorithm can discover a complete physical topology including inactive interfaces eliminated by the spanning tree protocol in metro Ethernet networks. The effectiveness of the algorithm is demonstrated by implementation.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.4
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• pp.71-79
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• 2011

This paper proposes a reliability enhancement of industrial real-time Ethernet using master redundancy method for NPPs(Nuclear Power Plants). In this paper, Ethernet Powerlink is investigated for distributed control systems for NPPs considering real-time and reliability performance. The proposed method can reduce a master switch-over time using PReq signal when Ethernet Powerlink master(Managing Node) failure was occurred. Using the OPNET simulation results, the performance enhancement of master switch-over time of Ethernet Powerlink is verified for NPPs.