• Proceedings of the Korean Operations and Management Science Society Conference
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• 2004.10a
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• pp.619-622
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• 2004

For recent years, hacking is in the trends of making excessive traffic unnecessarily to obstruct the service by getting a system's performance down. And we can also see systems paralyzed in service ability due to the flash crowds of normal traffic to a popular website. This is an important problem certainly solved in the point of QoS guarantee for the clients. It is known that the former is DDoS(Distributed Denial of Service) attack and the latter is FE(Flash Event). These two are samely anomalous traffic because these make excessive congestion on the network or system and downgrade the system's service ability. In this paper, we propose a scheme for protecting the system against anomalous traffic and for guaranteeing the QoS. For this, a server records and maintains the information of clients accessed more than one time before when it is in normal condition. When it falls into the congestion, the records are used for filtering the spoofed IP. We send and receive the ICMP request/reply packet to know whether the IP is spoofed. And we also propose for applying the object spliting of CDN to guarantee the QoS in the initial FE situation.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2002.05a
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• pp.252-255
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• 2002

As more critical services are provided in the internet, the risk to these services from malicious users increases. Several networks have experienced problems like Denial of Service(DoS) attacks recently. We analyse a network-based denial of service attack, which is called SYM flooding, to TCP-based networks. It occurs by an attacker who sends TCP connection requests with spoofed source address to a target system. Each request causes the targeted system to send instantly data packets out of a limited pool of resources. Then the target system's resources are exhausted and incoming TCP port connections can not be established. The paper is concerned with a detailed analysis of TCP SYN flooding denial of service attack. In this paper, we propose a Real Time Scan Detector(RTSD) mechanism and evaluate it\`s Performance.

• Journal of Sensor Science and Technology
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• v.14 no.6
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• pp.415-422
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• 2005

Using stretch sensors, a stuttering treatment training device that improve the abnormal breathing of stutterer was designed and developed. To improve stutterer's inadequate breathing method that is one of principal reason of stammering, the device estimates breathing method by checking the changes of the stretch sensor's resistances those are put on the chest and abdomen of user. And a vocal exercise program that carry out exercises only when the user maintains the abdominal breathing was designed. Using a PIC16C711 device that includes an A/D convertor, a main controller was designed and the vocal exercises software was developed using Director and C program with graphic user interface for user convenience. The controller sends the resistance data of sensors to PC through the serial port and the software verifies the breathing method. And the device was designed that the RTS (request to send) pin of serial port in PC is used as a power source so that it can work without any battery or other power source. Three stutterers have carried out the clinical experiments using the implemented device for two months and the results showed it was excellent to alleviate the stuttering.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.4
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• pp.885-892
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• 2013

In the model Utilizing the TCP / IP socket communication to transmit and receive data, if the size of data is small and if data-transmission aren't frequently requested, the importance of communication speed between a server and a client isn't emphasized. But nowadays, it has emerged for large amounts of data transfer requests and frequent data transfer request. This paper propose the TCP/IP communication model that can be improved the data transfer rate in multi-core environment by changing the receiving structure of the client to receive large amounts of data and the transmission structure of the server to send large amounts of data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7B
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• pp.827-833
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• 2011

Directional MAC protocols have drawn great attentions recently in super high speed wireless local/personal area networks due to their higher antenna gain, better spatial reuse, longer transmission range, and lower interference. Despite of these merits, directional MAC protocols suffer from deafness problem. The deafness problem occurs if a node does not answer an RTS frame addressed to it. To overcome this problem, directional MAC protocols have aimed at avoiding the deafness problem using multiple control frames or advance notice techniques or distinguishing deafness from collision. In this paper, we analyze the performance of these schemes in deafness environments with some scenarios. Through performance analysis, we compare the performance of these schemes through evaluating actual network throughput.

• ETRI Journal
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• v.43 no.4
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• pp.674-683
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• 2021

A trust-aware secure routing protocol (TSRP) for wireless sensor networks is proposed in this paper to defend against varieties of attacks. First, each node calculates the comprehensive trust values of its neighbors based on direct trust value, indirect trust value, volatilization factor, and residual energy to defend against black hole, selective forwarding, wormhole, hello flood, and sinkhole attacks. Second, any source node that needs to send data forwards a routing request packet to its neighbors in multi-path mode, and this continues until the sink at the end is reached. Finally, the sink finds the optimal path based on the path's comprehensive trust values, transmission distance, and hop count by analyzing the received packets. Simulation results show that TSRP has lower network latency, smaller packet loss rate, and lower average network energy consumption than ad hoc on-demand distance vector routing and trust based secure routing protocol.

• Journal of Korean Society of Transportation
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• v.19 no.6
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• pp.183-194
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• 2001

The centralized traffic information system is to gather and analyze real-time traffic information, to receive traffic information request from user, and to send user processed traffic information such as a path finding. Position information, result of destination search, and other information. In the centralized traffic information system, a server received path-finding requests from many clients and must process clients requests in time. The algorithm of multiple path-finding is needed for a server to process clients request, effectively in time. For this reason, this paper presents a heuristic algorithm that decreases time to compute path-finding requests. This heuristic algorithm uses results of the neighbor nodes shortest path-finding that are computed periodically. Path-finding results of this multiple path finding algorithm to use results of neighbor nodes shortest path-finding are the same as a real optimal path in many cases, and are a little different from results of a real optimal path in non-optimal path. This algorithm is efficiently applied to the general topology and the hierarchical topology such as traffic network. The computation time of a path-finding request that uses results of a neighbor nodes shortest path-finding is 50 times faster than other algorithms such as one-to-one label-setting and label-correcting algorithms. Especially in non-optimal path, the average error rate is under 0.1 percent.

• Journal of Internet Computing and Services
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• v.15 no.6
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• pp.9-14
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• 2014

In this paper, we propose AMV scheme which supports k-anonymization by using vectors for mobile clients. AMV can produces the minimal cloaking area using motion vector information of users (clients). The main reason for minimizing cloaking area is a server has to send the object information to all users who request the spatial queries. The experimental results show that the proposed AMV has superior performance over existing methods.

• The Journal of the Acoustical Society of Korea
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• v.34 no.6
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• pp.463-469
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• 2015

In this paper, we propose an underwater propagation delay-aware medium access control protocol and evaluate the performance of the proposed protocol. In the proposed propagation delay-aware medium access control protocol, a sink node can restore the received RTS frames that are not piled up in a slot time. We analyze and compare the performance of the proposed underwater propagation delay-aware medium access control protocol with that of the conventional medium access control protocol in various environments.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.3
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• pp.125-133
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• 2002

In this paper, we present an efficient broadcast protocol, called Btoken, that ensures total ordering of messages and atomicity of delivery in the large scaled distributed systems. Unlike the existing token-passing based protocol, Btoken does not circulate a token around the ring, instead, it uses three kinds of control messages for token transmission. The token has a sequence number field for broadcasting message, and the only site having the token can broadcast a message. When a site wishes to broadcast, It must send a message to the token site requesting the token. The token site sends a message with the token to the requester When the requester receives the token, it becomes the current token site and broadcasts a new message after setting sequence number derived from a field of the token into its message. Upon reception of it, any operating member is informed the position of the token site and will send token requesting message to the new token site. However, the other site may request the token to the old token site prior to receiving the broadcast message from the new token site. To resolve this problem, Btoken uses a message which is sent to the current token site by the old token site notifying who is the next token requester. Results of our simulation of the protocol show that Btoken is more efficient in the large scaled distributed system compared to existing broadcast protocols.