• Journal of Broadcast Engineering
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• v.21 no.3
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• pp.298-306
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• 2016

With the advent of Internet of Things (IoT) technology that allows the communications between things and devices over the Internet, a lot of researches on the IoT services, such as smart home or healthcare, have been progressed. In the existing machine-to-machine (M2M) communications, however, since the underlying link-layer technologies, such as Bluetooth or ZigBee, do not use the Internet Protocol (IP) communication, those technologies are not suitable to provide the IoT services. Accordingly, this paper discusses how to provide the Internet services in the M2M communication, and propose an implementation of the Constrained Application Protocol (CoAP) over 6LoWPAN for providing IoT services in the BLE networks. Based on the implementation, we compared the performance between HTTP and CoAP for IoT communications. From the experimental results, we can see that the CoAP protocol gives better performance than the HTTP protocol with two times higher throughput, 21% faster transmission time, and 22% smaller amount of generated packets.

• ETRI Journal
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• v.35 no.1
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• pp.27-34
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• 2013

This paper proposes a network-adaptive mechanism for HTTP-based video streaming over wireless/mobile networks. To provide adaptive video streaming over wireless/mobile networks, the proposed mechanism consists of a throughput estimation scheme in the time-variant wireless network environment and a video rate selection algorithm used to increase the streaming quality. The adaptive video streaming system with proposed modules is implemented using an open source multimedia framework and is validated over emulated wireless/mobile networks. The emulator helps to model and emulate network conditions based on data collected from actual experiments. The experiment results show that the proposed mechanism provides higher video quality than the existing system provides and a rate of video streaming almost void of freezing.

• Journal of Communications and Networks
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• v.18 no.5
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• pp.826-836
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• 2016

Increase of hypertext transfer protocol (HTTP)-based video popularity causes that broadband and Internet service providers' links transmit mainly multimedia content. Network planning, traffic engineering or congestion control requires understanding of the statistical properties of network traffic; therefore, it is desirable to investigate the characteristic of traffic traces generated, among others, by systems which employ adaptive bit-rate streaming. In our work, we investigate traffic originating from 120 client-server pairs, situated in an emulated laboratory environment, and multiplexed onto a single network link. We show that the structure of the traffic is distinct from the structure generated by first and second generation of HTTP video systems, and furthermore, not similar to the structure of general Internet traffic. The obtained traffic exhibits negative correlations, anti-persistence, and its distribution function is skewed to the right. Furthermore, we show that the traffic generated by clients employing the same or similar play-out strategies is positively correlated and synchronised (clustered), whereas traffic originated from different play-out strategies shows negative or no correlations.

• International journal of advanced smart convergence
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• v.12 no.1
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• pp.9-17
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• 2023

Recently, IoT technology has been widely used in many industries. Also research on integrating IoT technology with IoT sensors is actively underway. One of the important challenges in IoT is to support low-latency communication. With the development of communication networks and protocols, a variety of protocols are being used, and their performance is improving. In this paper, we compare the performance and analyze the characteristics of some of the major communication protocols in IoT application, namely MQTT, HTTP, and HTTPS. IoT sensors acquired data by connecting an Arduino equipped with ESP8266 and a temperature and humidity sensor (DHT11). The server measured the performance by building servers for each protocol using AWS EC2. We analyzed the packets transmitted between the Arduino and the server during the data transmission. We measured the amount of data and transfer time. The measurement results showed that MQTT had the lowest data transmission time and data amount among the three protocols.

• Annual Conference of KIPS
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• 2011.04a
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• pp.971-974
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• 2011

본 논문에서는 대용량 네트워크에 비정상적인 트래픽이 유입이 되거나 나가는 경우 패킷 기반의 비정상 트래픽의 탐지와 분석이 가능토록 하는 시스템을 설계하고 구현하였다. 본 논문에서 구현한 시스템은 네트워크상의 이상 행위를 탐지하기 위하여, DDoS HTTP Get Flooding 공격 탐지 알고리즘을 적용하고, NetFPGA를 이용하여 라우터 단에서 패킷을 모니터링하며 공격을 탐지한다. 본 논문에서 구현한 시스템은 Incomplete Get 공격 타입의 Slowloris 봇과, Attack Type-2 공격 타입의 BlackEnergy, Netbot Vip5.4 봇에 높은 탐지율을 보였다.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.586-588
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• 2005

WebDAV는 HTTP/1.1을 확장한 윕통신 프로토콜로서 인터넷을 통하여 다양한 콘텐츠의 비동기적인 협업 제작을 지원하기 위한 표준 하부구조를 제공한다. WebDAV명세를 지원하는 다양한 종류의 서버들은 사용자 상호간의 협업작업이 가능하게 해준다. 그리고 WebDAV 클라이언트는 서버와 HTTP 요청/응답 과정을 통하여 WebDAV 기능을 수행한다. 하지만 클라이언트 자체적으로 요청/응답 과정을 처리하는 것은 매우 복잡할 뿐만 아니라 비효율적이다. 따라서 WebDAV 기능을 잘 처리할 수 있는 클라리언트 라이브러리를 사용하는 것이 바람직하다. 본 논문에서는 WebDAV 클라이언트의 HTTP 요청/응답 처리를 위한 DAVon 클라이언트 라이브러리를 개발하였다. DAVon은 객체지향 기법으로 설계되어 C 라이브러리보다 편리한 API를 제공하고 리눅스 QT 라이브러리를 기반으로 구현되었다. 그리고 QT의 시그널/슬록 방식을 사용하여 HTTP 요청을 비동기적으로 처리함으로써 클라이언트의 병행성을 효율적으로 지원한다.

• ETRI Journal
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• v.43 no.3
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• pp.447-458
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• 2021

The quality of experience (QoE) of video streaming is degraded by playback interruptions, which can be mitigated by the playout buffers of end users. To analyze the impact of playout buffer dynamics on the QoE of wireless adaptive hypertext transfer protocol (HTTP) progressive video, we model the playout buffer as a G/D/1 queue with an arbitrary packet arrival rate and deterministic service time. Because all video packets within a block must be available in the playout buffer before that block is decoded, playback interruption can occur even when the playout buffer is non-empty. We analyze the queue length evolution of the playout buffer using diffusion approximation. Closed-form expressions for user-perceived video quality are derived in terms of the buffering delay, playback duration, and interruption probability for an infinite buffer size, the packet loss probability and re-buffering probability for a finite buffer size. Simulation results verify our theoretical analysis and reveal that the impact of playout buffer dynamics on QoE is content dependent, which can contribute to the design of QoE-driven wireless adaptive HTTP progressive video management.

• Journal of the Korea Society of Computer and Information
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• v.14 no.9
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• pp.47-54
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• 2009

Malicious codes, which are spread through WWW are now evolved with various hacking technologies However, detecting technologies for them are seemingly not able to keep up with the improvement of hacking and newly generated malicious codes. In this paper, we define the requirements of detecting systems based on the analysis of malicious codes and their spreading characteristics, and propose an improved detection scheme which monitors HTTP Outbound traffic and detects spreading malicious codes in real time. Our proposed scheme sets up signatures in IDS with confirmed HTML tags and Java scripts which spread malicious codes. Through the verification analysis under the real-attacked environment, we show that our scheme is superior to the existing schemes in satisfying the defined requirements and has a higher detection rate for malicious codes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.6
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• pp.341-349
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• 2014

Dynamic adaptive streaming over HTTP (DASH) is the most recent and promising technology to support high quality streaming services. In dynamic adaptive streaming over HTTP (DASH), a client consecutively estimates the available network bandwidth and decides the transmission rate for the forthcoming video chunks to be downloaded. In this paper, we propose a novel rate adaptation algorithm called quality of experience QoE-enhanced adaptation algorithm over DASH (QAAD), which preserves the minimum buffer length to avoid interruption and minimizes the video quality changes during the playback. We implemented a DASH test bed and conducted extensive experiments. Experimental results demonstrate that under fluctuating network conditions, QAAD provides seamless streaming with stabilized video quality while the previous buffer-aware algorithm (i.e., QDASH[9]) frequently changes the video quality and undergoes the interruption.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.904-914
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• 2017

For efficient energy usage, the concept of demand response has been emerged and thereby Open Automated D emand Response(OpenADR) protocol is developed as a standard protocol to provide automated demand response. There have been emerging trends on the demand response services using the Internet of Things(IoT) for smart h ome energy management. In this smart home energy IoT environment, a lightweight protocol is needed rather tha n the existing HTTP/ XML based OpenADR protocol for demand response services since many small devices wi ll be interconnected. In this paper, we propose a lightweight OpenADR protocol based on CoAP protocol for pro viding demand response service in Smart Energy IoT environment, implement the proposed CoAP-based protocol, and analyzed the performance compared to existing HTTP/ XML-based OpenADR 2.0b protocol.