• Proceedings of the Korea Information Processing Society Conference
• /
• 2010.04a
• /
• pp.729-732
• /
• 2010

통신망의 발달로 다양한 인터넷 기반 기술들이 등장함에 따라 현재는 데이터뿐만 아닌 음성에 대한 부분도 IP 네트워크를 통해 전송하려는 움직임이 발판이 되어 VoIP(Voice Over Internet Protocol)라는 기술이 등장하였다. SIP(Session Initiation Protocol) 프로토콜 기반 VoIP 서비스는 통신 절감 효과가 큰 장점과 동시에 다양한 부가서비스를 제공하여 사용자 수가 급증하고 있다. VoIP 서비스는 호(Call)를 제어하기 위해 SIP 기반으로 구성이 되며, SIP 프로토콜은 IP 망을 이용하여 다양한 음성과 멀티미디어 서비스를 제공하게 되는데 IP 프로토콜에서 발생하는 인터넷 보안 취약점을 그대로 동반하기 때문에 DoS(Denial of Service) 및 DDoS(Distribute Denial of Service)에 취약한 성향을 가지고 있다. DDoS 공격은 단시간 내에 대량의 패킷을 타깃 호스트 또는 네트워크에 전송하여 네트워크 접속 및 서비스 기능을 정상적으로 작동하지 못하게 하거나 시스템의 고장을 유도하게 된다. 인터넷 기반 생활이 일상화 되어 있는 현 시점에서 안전한 네트워크 환경을 만들기 위해 DDoS 공격에 대한 대응 방안이 시급한 시점이다. DDoS 공격에 대한 탐지는 매우 어렵기 때문에 근본적인 대책 마련에 대한 연구가 필요하며, 정상적인 트래픽 및 악의적인 트래픽에 대한 탐지 시스템 개발이 절실히 요구되는 사항이다. 본 논문에서는 SIP 프로토콜 및 공격기법에 대해 조사하고, DoS와 DDoS 공격에 대한 특성 및 종류에 대해 조사하였으며, SIP를 이용한 VoIP 서비스에서 IP 분류와 메시지 중복 검열을 통한 DDoS 공격 탐지기법을 제안한다.

• Journal of the Korea Society for Simulation
• /
• v.18 no.1
• /
• pp.27-34
• /
• 2009

Currently network users, especially the number of internet users, increase rapidly. Also, high quality of service is required and this requirement results a sudden network traffic increment. As a result, an efficient management system for huge network traffic becomes an important issue. Ontology/data engineering based context awareness using the System Entity Structure (SES) concepts enables network administrators to access traffic data easily and efficiently. The network traffic analysis system, which is studied in this paper, is designed and implemented based on a model and simulation using data engineering methodology to be avaiable in evaluating large network traffic data. Extensible Markup Language (XML) is used for metadata language in this system. The information which is extracted from the network traffic analysis system could be modeled and simulated in Discrete Event Simulation (DEVS) methodology for further works such as post simulation evaluation, web services, and etc.

• Journal of Korea Society of Industrial Information Systems
• /
• v.14 no.5
• /
• pp.11-18
• /
• 2009

Ajax based on Java Script receives attention as an alternative to ActiveX technology. Most portal sites in korea show a tendency to reopen existing services by combining the technology, because it supports most web browsers, and has the advantages of such a brilliant interface, excellent speed, and traffic reduction through asynchronous interaction. This paper modeled and implemented a multilingual meta-search service using the Ajax and open APIs provided by international famous sites. First, a Korean query is translated into one of the language of 54 countries around the world by Google translation API, and then the translated result is used to search the information of the social web sites such as Flickr, Youtube, Daum, and Naver. Searched results are displayed fast by dynamic loading of portion of the screen using Ajax. Our system can reduce server traffic and per-packet communications charges by preventing redundant transmission of unnecessary information.

• Journal of the Korea Society of Computer and Information
• /
• v.14 no.4
• /
• pp.111-117
• /
• 2009

Improvement of Wireless internet and handheld devices makes it possible that users can use various multimedia services. But, access point devices are needed while using handheld devices, and those devices use virtual network address for networking. For that reason, end-users hardly use the 1:1 voice or video chat, and messenger service that require direct communications between devices. Also, service providers need central server for relaying packets from terminals to others, the traffic and costs of relaying go high, so real-time massive data transmission services are restrictively provided. In this study, we apply TCP/UDP hole punching technique to those applications. And we implement service that supports real-time multimedia direct transmission between equipments that use virtual network addresses.

• The Journal of the Acoustical Society of Korea
• /
• v.42 no.3
• /
• pp.262-269
• /
• 2023

In this paper, we propose a Linear Prediction (LP) analysis-based feature for detecting Snapping Shrimp (SS) Noise (SSN) in underwater acoustic data. SS is a species that creates high amplitude signals in shallow, warm waters, and its frequent and loud sound is a major source of noise. The proposed feature takes advantage of the characteristic of SSN, which is sudden and rapidly disappearing, by using LP analysis to detect the exact noise interval and reduce the effects of SSN. The error between the predicted and measured value is large and results in effective SSN detection. To further improve performance, a constant false alarm rate detector is incorporated into the proposed feature. Our evaluation shows that the proposed methods outperform the state-of-the-art MultiLayer-Wavelet Packet Decomposition (ML-WPD) in terms of receiver operating characteristic curve and Area Under the Curve (AUC), with the LP analysis-based feature achieving a higher AUC by 0.12 on average and lower computational complexity.

• Journal of KIISE:Information Networking
• /
• v.30 no.3
• /
• pp.329-342
• /
• 2003

Most of the existing multicast routing protocols for ad-hoc networks do not take into account the efficiency of the protocol for the cases when there are large number of sources in the multicast group, resulting in either large overhead or poor data delivery ratio when the number of sources is large. In this paper, we propose a multicast routing protocol for ad-hoc networks, which particularly considers the scalability of the protocol in terms of the number of sources in the multicast groups. The proposed protocol designates a set of sources as the core sources. Each core source is a root of each tree that reaches all the destinations of the multicast group. The union of these trees constitutes the data delivery mesh, and each of the non-core sources finds the nearest core source in order to delegate its data delivery. For the efficient operation of the proposed protocol, it is important to have an appropriate number of core sources. Having too many of the core sources incurs excessive control and data packet overhead, whereas having too little of them results in a vulnerable and overloaded data delivery mesh. The data delivery mesh is optimally reconfigured through the periodic control message flooding from the core sources, whereas the connectivity of the mesh is maintained by a persistent local mesh recovery mechanism. The simulation results show that the proposed protocol achieves an efficient multicast communication with high data delivery ratio and low communication overhead compared with the other existing multicast routing protocols when there are multiple sources in the multicast group.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37 no.2B
• /
• pp.130-137
• /
• 2012

In this paper, we propose core and edge router architectures with LPI(Low Power Idle) for reducing energy consumption in OBS networks. The proposed core router architecture is comprised of a BCP switch, a burst switch, line cards and sleep/wake controller for LPI. When the offered load of network is low, sleep/wake controller can change the state of the core router line card from active to sleep state for saving the energy after receiving network control packet. The edge router consists of a switch for access line card, a SCU and OBS edge router line cards. The LPI function in edge router line card is performed through network level control by network control packet, individually. Additionally, PHY/transceiver modules can transition active state to sleep state when burst assemble engine generates new bursts. To evaluate the energy saving performance of proposed architecture with LPI, the power consumption of each router is analyzed by using data sheet of commercial router and optical device. And, simulation is also performed in terms of sleep time of PHY/Transceiver through OPNET.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.11
• /
• pp.5479-5486
• /
• 2012

In this paper, we have measured PRR, RSSI and LQI of ZigBee channels under Wi-Fi environment and have assessed channel characteristic and link quality. To confirm any relationship among RSSI, LQI values and PRR under Wi-Fi interference in overlapping and non-overlapping channels of Wi-Fi and ZigBee, the experiments were performed without Wi-Fi, with Wi-Fi and file download through Wi-Fi. Under Wi-Fi interference, We perfomed experiments to ensure channel characteristics and link quality by fixing Wi-Fi and ZigBee receiver and varying the distance between ZigBee receiver and transmitter. ZigBee transmitter sends packet of 256 bits every second to ZigBee receiver. PRR was measured from ZigBee with variance of distance between fixed Wi-Fi and ZigBee. RSSI, LQI, PRR were measured from ZigBee with fixed Wi-Fi, fixed ZigBee receiver and variance of distance of ZigBee transmitter. As a result, we confirmed decrease of PRR under Wi-Fi interference but RSSI, LQI values similar regardless of overlapped or non-overlapped channel and Wi-Fi interference. Therefore, PRR should be used for interference detection in ZigBee communication under Wi-Fi environment but RSSI and LQI are not appreciate.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.16 no.4
• /
• pp.31-40
• /
• 2016

In vehicular ad-hoc networks (VANETs), vehicles sense information on emergency incidents (e.g., accidents, unexpected road conditions, etc.) and propagate this information to following vehicles and a server to share the information. However, this process of emergency message propagation is based on multiple broadcast messages and can lead to broadcast storms. To address this issue, in this work, we use a novel approach to detect the vehicles that are farthest away but within communication range of the transmitting vehicle. Specifically, we discuss a signal-to-noise ratio (SNR)-based linear back-off (SLB) scheme where vehicles implicitly detect their relative locations to the transmitter with respect to the SNR of the received packets. Once the relative locations are detected, nodes that are farther away will set a relatively shorter back-off to prioritize its forwarding process so that other vehicles can suppress their transmissions based on packet overhearing. We evaluate SLB using a realistic simulation environment which consists of a NS-3 VANET simulation environment, a software-based WiFi-IP gateway, and an ITS server operating on a separate machine. Comparisons with other broadcasting-based schemes indicate that SLB successfully propagates emergency messages with latencies and hop counts that is close to the experimental optimal while reducing the number of transmissions by as much as 1/20.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.12
• /
• pp.2450-2460
• /
• 2015

Recently, as interest in IoT (Internet of Things) increase, research and standardization of a new protocol which reflects the characteristics of IoT has progressed. Among them, RPL(IPv6 for Low-Power Lossy Network) is a standardized routing protocol for IoT. RPL utilizes DIO (DODAG Information Object) messages which is flooded from the sink node to the whole network for path establish and maintenance. However, in large scale networks, not only a long time is required to propagate the DIO message to the whole networks but also a bottleneck effect around the sink node is occurred. Multi-sink based approaches which take advantage of reducing routing overhead and bottleneck effect are widely used to solve these problems. In this paper, we define 'unnecessary path update problems' that may arise when applying the RPL protocol to the multi sink based IoT networks and propose two methods namely Routing Metric based Path Update Decision method and Immediate Successor based Path Update Decision method for selective routing update.