• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.3
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• pp.303-308
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• 2016

Recently, as the rapid development of network technology and the increase of services required high bandwidth such as multimedia service, the network traffic dramatically increases. This massive increase of network traffic causes some problems such as the degradation of QoS and the lack of network resources and, to solve these problems, various research to guarantee QoS have been performing. Currently, The most representative method to guarantee the QoS is the DiffServ(: Differentiated Service). The DiffServ defines the AF(: Assured Forwarding) PHB(: Per Hop Behavior) and statistically ensures the throughput over the certain level of data rate. However, the TCP congestion control method that make up the majority of the Internet traffic is not fundamentally suitable to the DiffServ that guarantees the throughput without managing the individual flow. Therefore, in this paper, we present this mismatch through the simulation as an example and propose the solution by controlling the TCP of the terminal in the network. The proposed scheme utilizes the information of the reception window size included in the ACK frame and does not require any modification of the TCP algorithms currently in use.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1B
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• pp.144-153
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• 2010

Flooding based routing protocols are usually used to disseminate information in wireless sensor networks. Those approaches, however, require message retransmissions to all nodes and induce huge collision rate and high energy consumption. In this paper, HoGoP (Hop based Gossiping Protocol) in which all nodes consider the number of hops from sink node to them, and decide own gossiping probabilities, is introduced. A node can decide its gossiping probability according to the required average reception percentage and the number of parent nodes which is counted with the difference between its hop and neighbors' ones. Therefore the decision of gossiping probability for network topology is adaptive and this approach achieves higher message reception percentage with low message retransmission than the flooding scheme. Through simulation, we compare the proposed protocol with some previous ones and evaluate its performance in terms of average reception percentage, average forwarding percentage, and forwarding efficiency. In addition, average reception percentage is analyzed according to the application requirement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4B
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• pp.298-305
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• 2003

In this paper, we proposed a high performance lookup controller for IP packet forwarding engine of ATM based label edge routers. The lookup controller is designed to provide services such as MPLS, VPN, ELL, and RT services as well as the best effort. For high speed searching for IP addresses, we employed a TCAM based hardware search device not using traditional algorithmic approaches. We also implement lookup control functions into FPGA for fast processing of packet header and lookup control. The proposed lookup controller is designed to support differenciated services for users and to process in pipelined mechanism for performance improvement. A two-step search scheme is also applied to perform lookup for the key combined with multi-field of packet header. We found that the proposed lookup controller provides the performance of about 16M packets per second through simulations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.2
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• pp.247-268
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• 2011

Due to the application-specific nature of wireless sensor networks, the sensitivity to such a requirement as data reporting interval varies according to the type of application. Such considerations require an application-specific, parameter tuning paradigm allowing us to maximize energy conservation prolonging the operational network lifetime. In this paper, we propose a reporting interval adaptive, sensor control platform for energy-saving data gathering in wireless sensor networks. The ultimate goal is to extend the network lifetime by providing sensors with high adaptability to application-dependent or time-varying, reporting interval requirements. The proposed sensor control platform is based upon a two phase clustering (TPC) scheme which constructs two types of links within each cluster - namely, direct link and relay link. The direct links are used for control and time-critical, sensed data forwarding while the relay links are used only for multi-hop data reporting. Sensors opportunistically use the energy-saving relay link depending on the user reporting, interval constraint. We present factors that should be considered in deciding the total number of relay links and how sensors are scheduled for sensed data forwarding within a cluster for a given reporting interval and link quality. Simulation and implementation studies demonstrate that the proposed sensor control platform can help individual sensors save a significant amount of energy in reporting data, particularly in dense sensor networks. Such saving can be realized by the adaptability of the sensor to the reporting interval requirements.

• Convergence Security Journal
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• v.21 no.1
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• pp.129-135
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• 2021

Greedy protocols show good performance in Vehicular Ad-hoc Networks (VANETs) environment in general. But they make longer routes causing by surroundings or turn out routing failures in some cases when there are many traffic signals which generate empty streets temporary, or there is no merge roads after a road divide into two roads. When a node selects the next node simply using the distance to the destination node, the longer route is made by traditional greedy protocols in some cases and sometimes the route ends up routing failure. Most of traditional greedy protocols just take into account the distance to the destination to select a next node. Each node needs to consider not only the distance to the destination node but also the direction to the destination while routing a packet because of geographical environment. The proposed routing scheme considers both of the distance and the direction for forwarding packets to make a stable route. And the protocol can configure as the surrounding environment. We evaluate the performance of the protocol using two mobility models and network simulations. Most of network performances are improved rather than in compared with traditional greedy protocols.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3587-3594
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• 2022

A distributed high-speed data acquisition and monitoring system for the RF negative ion source at Huazhong University of Science and Technology (HUST) is developed, which consists of data acquisition, data forwarding and data processing. Firstly, the data acquisition modules sample physical signals at high speed and upload the sampling data with corresponding absolute-time labels over UDP, which builds the time correlation among different signals. And a special data packet format is proposed for the data upload, which is convenient for packing or parsing a fixed-length packet, especially when the span of the time labels in a packet crosses an absolute second. The data forwarding modules then receive the UDP messages and distribute their data packets to the real-time display module and the data storage modules by PUB/SUB-pattern message queue of ZeroMQ. As for the data storage, a scheme combining the file server and MySQL database is adopted to increase the storage rate and facilitate the data query. The test results show that the loss rate of the data packets is within the range of 0-5% and the storage rate is higher than 20 Mbps, both acceptable for the HUST RF negative ion source.

• Journal of the Korea Society of Computer and Information
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• v.21 no.5
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• pp.49-56
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• 2016

Increasing Internet traffic and forwarding table size need high performance IP address lookup engine which is a crucial function of routers. For finding the longest matching prefix, trie-based or its variant schemes have been widely researched in software-based IP lookup. As a software router, we enhance the IP address lookup engine using GPU which is a device widely used in high performance applications. We propose a data structure for multibit trie to exploit GPU hardware efficiently. Also, we devise a novel scheme that the root subtrie is loaded on Shared Memory which is specialized for fast access in GPU. Since the root subtrie is accessed on every IP address lookup, its fast access improves the lookup performance. By means of the performance evaluation, our implemented GPU-based lookup engine shows 17~23 times better performance than CPU-based engine. Also, the fast access technique for the root subtrie gives 10% more improvement.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.6
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• pp.721-729
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• 2016

CCN(Content-Centric Network) enables users to retrieve content using the content's name. Researchers face critical challenges in terms of mobility. Since the routing information is part of the content name, when the provider moves, it is necessary to update all the routers routing information. However, this requires significant costs. In this paper, we propose PNPCCN(Proactive Neighbor Pushing CCN), considering the popularity and rarity of mobility support, for providers in CCN environments. Via simulation studies, we demonstrate that our solutions are effective in terms of shorter numbers of retransmitted Interest packets, and average download times and higher delivery ratios during mobility.

• The Journal of Society for e-Business Studies
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• v.1 no.1
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• pp.227-247
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• 1996

Presented in this paper is a control model for developing virtual factory simulator, which is being operated under the distributed environment. The control model consists of production activity plan and information flows. To incorporate elements of the characteristics of the distributed control system, we suggested a collaboration model. This model is working under the client/server architecture, and also designed for cooperative-distributed shop control(CDSC) system in order to exploit several advantages of client/server architecture. Collaboration among each agent(or client) is done through negotiation and task sharing. Based on a contract net model, the CDSC system has three kinds of agents-order agent, resource agent, and communication forwarding agent. Each agent performs shop scheduling and control through negotiation on contract net. No node in CDSC system can have authority over other node. A bidding scheme is employed far negotiation between order agent and resource agents. The CDSC system can support re-negotiation among resource agents and an algorithm for re-negotiation is also developed. Experimental results are shown to advocate the effectiveness of the CDSC system for CIM environments.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.10b
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• pp.1279-1282
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• 2001

최근 인터넷의 급속한 사용 증가로 인해 전송 링크의 광대역 지원과 멀티미디어 트래픽의 QoS 보장 문제, 향상된 IP 서비스의 제공 문제 해결은 필수적이다. MPLS 기술은 IP의 유연성과 확장성을 제공할 수 있는 패러다임의 하나이다. MPLS 망의 경계에 위치하는 LER 은 링크 계층 뿐만 아니라 IP 계층에서도 패킷을 전달해야 한다. 본 논문에서는 하드웨어 포워딩 엔진을 갖는 MPLS LER에서, 패킷 필터링 기능을 지원하기 위해서 포워딩 엔진을 제어하기 위한 기법에 대해서 기술한다. 이러한 패킷 필터링 기능은 MPLS LER에 firewall 기능을 제공하는데 응용될 수 있다.