• The Journal of the Korea Contents Association
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• v.5 no.2
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• pp.257-266
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• 2005

As developing of the internet and computer technology, more interests are gathered to the conference service which provides capability of multi-party real-time visual conference. In this paper, we have designed and implemented a SIP-based visual conference system which includes Presence service. The elements of this conference system are user system, which has conference UA(User Agent) capability, presence seuer and conference server. For the presence service, we have adapted publication method which uses SIP PUBLISH message, and with this service various status informations of users are easily acquired. Also invitations and involvements to the conference are easily made through this service. For the conference server which controls establishment and management of multi-party connections, we have included conference event package. This package provides dynamically changing conference informations and users informations through SIP subscription and notification functions.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.04b
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• pp.1555-1558
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• 2002

SIP는 간단한 텍스트 기반의 응용계층 프로토콜로서, H.323을 대체할 수 있는 프로토콜이다. SIP는 인터넷 환경에 그대로 접목 할 수 있고, 새로운 기능 및 부가서비스의 제공이 용이하다는 장점을 가지고 있다. SIP 프로토콜은 요청메시지와 그에 대한 응답으로 구성되는 Request-Response방식이다. SIP의 장점은 유일한 개인 ID를 이용하여 장소와 단말기에 구애를 받지 않고 SIP서비스를 제공받을 수 있는 Personal Mobility Service에 있다. 본 논문에서는 User Agent와 프록시 서버(Proxy Server) 사이에 이루어지는 SIP 트랜잭션(Transaction)을 Call-Flow를 통해서 살펴보고자 한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.489-492
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• 2011

SIP (Session Initiation Protocol)는 사용자간의 멀티미디어 세션의 초기화, 변경 및 종료를 위한 응용 계층의 시그널링 프로토콜이다. SIP는 실시간 멀티미디어 서비스 통신에 많이 이용되기 때문에 주로 Unreliable Transport Protocol을 사용한다. 따라서 손실된 SIP 메시지들의 신뢰성을 보장하기 위하여 재전송 메커니즘을 제공한다. 하지만 이러한 재전송 메커니즘은 SIP 프록시 서버가 과부하 상황일 경우 신뢰성보다는 오버헤드가 증가되는 문제점을 가진다. 기존의 여러 SIP 과부하 제어 방법이 제안되었지만 네트워크 혼잡이 증가함에 따라 프록시 서버의 처리율이나 호 설정 시간의 지연 문제를 효율적으로 해결하지 못한다. 본 논문에서는 SIP 시그널링 네트워크에서 프록시 서버가 과부하 상황일 경우 낮은 호 설정 지연시간과 높은 처리율을 위해 우선순위 스케줄링 기반의 과부하 제어 알고리즘을 제안한다. 그리고 기존 과부하 제어에서 사용하는 알고리즘과 제안하는 알고리즘을 비교하여 보았다. 성능 평가 결과 부하에 따른 프록시 서버의 처리율과 호 설정 시간의 지연 측면에서 기존의 과부하 제어 알고리즘보다 향상됨을 보였다.

• The Journal of the Korea Contents Association
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• v.10 no.1
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• pp.46-58
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• 2010

The user valence of VoIP services with SIP protocol is increasing rapidly because of cheap communication cost and its conveniency. But attacker can easily modify the packet contents of SIP protocol as SIP header is transmitted by using UDP methods in text form. The reason is that SIP protocols does not provide an authentication function on the transmission session. Therefore, existing SIP protocol is very weak on SIP Packet Flooding attack etc. In order to solve like this kinds of SIP vulnerabilities, we used SIP status codes under the monitoring module for detecting SIP Flooding attacks and additionally proposed an advanced protocol where the authentication and security function is strengthened about SIP packet. We managed SIP session spontaneously in order to strengthen security with SIP authentication function and to solve the vulnerability of SIP protocol. The proposed mechanism can securely send SIP packet to solves the security vulnerability with minimum traffic transmission. Also service delay in SIP proxy servers will be minimized to solve the overload problem on SIP proxy server.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.585-588
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• 2005

The Presence Agent Server receives user's presence information via PUBLISH request message and let subscribers to know that information. IMPP client has a functions for PUA(presence user agent) as a base operational entity. In some circumstance, the client has both pua and pa logical entities. However presence agent server has take part only of PA. In this paper, we describes the design and implementation that contains modules based configurations and approaches for presence agent server. Also, we describe how we handle each events and database API instruction set.

• KIPS Transactions on Computer and Communication Systems
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• v.3 no.4
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• pp.115-124
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• 2014

Since it costs a lot to build a home network system of new service provider, the entry barrier is quite high. If it would be possible to build a home network system with high performance at a low building cost, it would be quite attractive. If a home network would be built in P2P-SIP(Peer to peer - Session Initiation Protocol) structure, it is possible to decrease server maintenance cost and keep high usability by deconcentrating the traffic concentrated on the server. It is also possible to efficiently manage the location information of terminal, if quorum system based on fuzzy logic would be applied. In this paper we propose the P2P-SIP structure applied of quorum system based on fuzzy logic by which a home network system can be built at low cost. It was possible to know by comparing the structure with existing one that the structure has very good performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.11
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• pp.2678-2684
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• 2014

In this paper a new message control method that can reduce server load and network traffic in XMPP/SIP presence service system has been proposed. This presence service system can process both XMPP(Extensible Massaging and Presence Protocol) based presence information and SIP(Session Initiation Protocol) based presence information. A new XMPP stanza architecture with added elements for presence stanza and IQ stanza has been designed, and a new presence information data processing method which can reduce size of SIP notification message and SIP PUBLISH message has been suggested. Furthermore a messages exchanging procedure that can transfer presence information between XMPP domain and SIP domain has been also suggested. The performance of the proposed system has been analysed by simulation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.108-112
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• 2002

인터넷을 이용한 여러 응용 서비스들 중에서 저렴한 비용으로 음성을 전송할 수 있는 VoIP 서비스의 발전으로 사용자의 급격한 증가가 예상된다. VoIP에 mobility, universal number, multiparty conference, voice mail, automatic call distribution과 같은 고품질의 서비스를 제공하기 위해서는 시그널링이 가능한 표준화된 프로토콜이 필요하다. 현재 IETF의 SIP(Session Initiation Protocol)가 빠른 호 설정과 parsing 및 compile이 쉬운 장점으로 인해 SIP를 기반으로 한 VoIP 서비스를 제공하기 위해 국내외적으로 SIP 기반 구성요소에 대한 개발에 박차를 가하고 있다. 본 논문에서는 사용자가 보내는 request(INVITE) method를 처리해주는 SIP 서버의 부하 경감, 망 운용의 효율성, 많은 사용자에 대한 서비스를 제공하기 위해 새로운 서버 유형인 Hybrid형 SIP 서버를 제시하고자 한다.

• The Journal of the Korea Contents Association
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• v.7 no.3
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• pp.34-41
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• 2007

The presence service which provides user's presence information by subscription and notification is one of SIP(session initiation protocol) extension services, and it is used importantly in VoIP(Voice over IP) and Instant Messaging service. In this paper, we propose a new method in which users can combine and control presence service and call processing services in various ways by extending call processing language, and only changed parts of the presence information are published instead of full presence information document. Each user registers full presence information document with his own call processing script during the first publication to a presence server. The presence server executes these call processing scripts, so it can provide various services with combination of presence service and call processing services during the presence subscriptions and notifications. Afterwards, users publish only changed parts of the presence information and the presence server notify only these changed parts to watchers. Therefore the efficiency of the overall system can be improved. The performance of our proposed model is evaluated by experiments.

• Journal of the Korea Society of Computer and Information
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• v.13 no.7
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• pp.199-205
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• 2008

The centralized conference model has advantage of conference management and control. however it's scalability has been limited as performance degrades largely with increasing number of conference users. So new distributed conference models which improve scalability of centralized conference model have been suggested recently. In the distributed conference model. as conference users exceed a predefined maximum number, a new conference server is added to the conference dynamically. In this paper, We have proposed a new method which increases efficiency of conference event package processing that primary conference server should charge in the distributed conference environment. The primary conference server exchanges informations with each secondary conference servers and conference users by using conference event package. And from the conference information database it selects SIP(Session Initiation Protocol) UA(User Agent) which will share notification to the conference users, and transfers lists to each conference servers. The conference servers make the selected UAs share processing of conference event package, so loads of SIP signal processing decrease, and improve scalability of distributed conference model. The performance of our proposed model is evaluated by experiments.