• The KIPS Transactions:PartC
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• v.11C no.3
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• pp.371-378
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• 2004

SIP(Session Initiation Protocol) is a text based call signaling protocol that has characteristics such as flexibilities and extensibility for various application services over Internet. In this paper, we have implemented SIP based integrated Instant Messenger system which includes Presence Watcher Information service that can notify various current users status. In this system, voice and video communications are also possible as well as text based instant messages. For voice and video communication, we have newly proposed a method in which direct connection is possible between users without creation of SW INVITE dialog by extending PRESENCE TUPLE of presence information. In this case, PRESENCE TUPLE stores some informations necessary for the session.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.8
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• pp.4025-4042
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• 2017

Session initiation protocol (SIP) is a kind of powerful and common protocols applied for the voice over internet protocol. The security and efficiency are two urgent requirements and admired properties of SIP. Recently, Hamed et al. proposed an efficient authentication and key agreement scheme for SIP. However, we demonstrate that Hamed et al.'s scheme is vulnerable to de-synchronization attack and cannot provide anonymity for users. Furthermore, we propose an improved and efficient authentication and key agreement scheme by using elliptic curve cryptosystem. Besides, we prove that the proposed scheme is provably secure by using secure formal proof based on Burrows-Abadi-Needham logic. The comparison with the relevant schemes shows that our proposed scheme has lower computation costs and can provide stronger security.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.622-624
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• 2005

최근까지 데이터망에 음섬을 올려 전송하는 연구가 비약적으로 진행되면서 SIP를 지원하는 제품들이 응용되어 상용화 되고 있다. 사설망을 가지는 PBX도 시장 요구에 따라 점차 음성 회선 연결을 위해 SIP 기능을 적용하여 IP PBX의 모습으로 진화하고 있다. 그러나 IP PBX는 외부 SIP망에만 연결하기 보다는, ISDN/PSTN과 같은 기존의 공용망과 함께 연결하여 내부 사설망과 외부 공용망을 연결한다. 이 경우 상이한 외부 프로토콜을 융합하여 내부망과 연결하는 기능이 IP PBX에 포함 되어야 한다. 본 연구에서는 이 역할을 담당하는 내부 모듈을 컴포넌트로 추출하고, 상이한 프로토콜의 기능을 통합하여 수행할 수 있도록 인터페이스를 정의하여 성능 향상을 위한 방법론을 제안한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.11a
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• pp.1181-1184
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• 2008

본 논문에서는 멀티미디어 공동 작업 환경의 세션 초기 프로토콜(SIP: Session Initiation Protocol)에서 오류 상호 인지 및 제어에 대하여 기술한다. 상호 인지란 상호 작업 이해, 참여자 관계 설정 등 결합이라는 구현 기술을 말한다. 결합에는 변화하는 내용을 인지하는 동적 인지와 자주 변하지 않는 정적 인지가 있는 데 제안하고자 하는 오류 제어는 멀티미디어 공동 작업 환경에서 오류 발생시 오류도 하나의 응용으로 취급한다. 본 연구에서는 윈도우 오버레이 기능에 세션 제어, 발언권 제어 등을 추가한 윈도우 공유 방법을 제안한다. 공동 작업 환경에 참여하는 모든 사용자들은 사용자의 명령, 또는 오류가 발생된 응용들을 제어 가능하며 상호 작용 가능하다.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.05a
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• pp.152-155
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• 2008

본 논문에서는 멀티미디어 응용 개발 프레임워크의 세션 초기 프로토콜(SIP: Session Initiation Protocol)에서 다채널 방식을 사용한다. 우선 기본적으로 문자 채널과 제어/오류 제어 채널을 고정할당하며 미디어의 채널을 동적 할당한다. 고정할당 채널은 채널요청이 없어도 세션 개설 요청이 있으면 자동적으로 생성하며, 미디어 데이터는 별도의 채널을 할당하여 채널 별로 단일 미디어 정보를 순서대로 전송 함으로서 동일 미디어 데이터는 순서가 변할 우려는 없다. 그러나 이러한 다채널방식에서는 미디어간 동기화 문제를 유발 시키는데 수신 측에서는 새로 발생된 데이터의 시작 시점을 서로 맞춤으로서 미디어간 동기화를 실현하였다. 새로운 미디어의 시작 시 항상 제어 데이터를 먼저 전송하여 새로운 미디어 데이터의 생성을 모든 참여자 프로세스에 알린다. 수신 측에서는 새로 발생된 데이터의 시작 시점을 서로 맞춤으로서 미디어간 동기화를 실현한다. 오류의 동기화도 동일한 방법을 사용한다.

• 한국ITS학회:학술대회논문집
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• 2002.11a
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• pp.129-133
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• 2002

• 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.

• Journal of the Korea Society of Computer and Information
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• v.12 no.6
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• pp.187-192
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• 2007

Conference focus maintains and manages SIP(Session Initiation Protocol) signal connections with total conference participants, and it plays core functions of conference server. When the number of conference participants increases, conference focus restricts scalability of conference as increasing quantify of messages for processing. In this paper, to solve this problem. we propose a user system(conference information agent), which receives conference information from the conference focus and transfers them to the participants it manages. And we design and implement the total system including conference focus. When the conference information agent subscribe to the conference focus, it shows its possession of agent capability and capacity by using SIP SUBSCRIBE message. The conference focus informs to the other party by SIP response message that it was chosen as a conference information agent, and after that the conference focus sends all conference notification messages to it. So load of the conference focus can be reduced by this method. Finally, we have analyzed the performance of our system 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.

• Journal of the Korea Society of Computer and Information
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• v.14 no.5
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• pp.85-91
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• 2009

The centralized conference architecture has a restriction in scalability due to the performance reduction as the number of conference participants increases. To solve this problem several distributed conference architectures have been studied recently. In these architectures new conference servers are added dynamically to the conference environment. In this paper, We have proposed a new conference information data model which can be used in these distributed conference architectures. In our newly proposed conference information data model. several components has been added for exchanging conference information between primary conference server and multiple secondary conference servers. We also proposed a procedure of conference information exchange between these conference servers. And the management of conference informations and SIP(Session Initiation Protocol) notifications to the total conference participants can be processed distributedly with these conference servers, therefore the load to the primary conference server can be decreased by using this method. The performance of our proposed model has been evaluated by experiments.