• The Journal of the Korea Contents Association
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• v.15 no.12
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• pp.18-23
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• 2015

This paper proposes a new protection technique against deregistration attack in SIP. Although it is caused by simple spoofing the REGISTER message of a legitimate SIP UA, its impact is serious. This new protection technique identifies and protects the deregistration attack by removing a binding form the location server after delaying a certain period of time instead of removing the binding immediately after receiving deregistration message. Therefore, this technique makes it possible to establish a secure SIP environment defending the deregistraion attack without any additional overhead such as an encryption or authentication.

• Journal of the Korea Society of Computer and Information
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• v.15 no.12
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• pp.67-73
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• 2010

In SIP(Session Initiation Protocol) environment, the presence event notification operation makes presence service user to recognize presence information status changes of the other party. In conventional method, the user should send each SIP SUBSCRIBE message containing the address of the other party to the presence server. Furthermore each presence subscription requires refresh messages, and the amount of notification messages from the other party becomes large. These facts increases network traffic and the load of presence server. In this paper, to solve these problems a new presence list service has been suggested. It uses a presence list consists of URI of the other party and make it possible to subscribe by using one SUBSCRIBE message. So this method decreases the amount of SUBSCRIBE messages and refresh messages, and it also decreases the amount processing event notification messages from the subscribed the other party. And to increase the efficiency, a presence filtering method which enables to include some parts of selected presence information into the notification message body has been also suggested. The implemented system can reduce SIP message related network traffic and message processing time of the presence server. The performance of this proposed system has been evaluated by experiments, and the results showed decreasing of server processing time.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.4
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• pp.929-935
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• 2008

As internet telephony services based on Session initiation Protocol (SIP) enter the spotlight as marketable technology, many products based on SIPs have been developed and utilized for home and office telephony services. The call connection of an internet phone is classified into specific call connections and group call connections. Group call connections have a forking function which delivers the message to all of the group members. This function requires excessive message control for a call connection and creates heavy traffic in the network. In the internet cail system model. most of the call-setup messages are directed to the proxy server during a short time period. This heavy message load brings an unwanted delay in message processing and. as a result, call setup can not be made. To solve the delay problem, we simplified the analysis of the call-setup message in the proxy server, and processed the forking function distributed for the group call-setup message. In this thesis, a new system model to minimize the load is proposed and the subsequent implementation of this model demonstrates the performance improvement.

• The Journal of the Korea Contents Association
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• v.4 no.1
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• pp.83-89
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• 2004

Instant messaging(IM) service is one of the useful communication means in the Intemet for exchanging simple messages between users. Usually, IM service is coupled with Presence service which provides status information of users. In this case, instant messages are sent and received directly between on-line users. Therefore, messages could not be exchanged when users are in off-line state. In this paper, We have implemented SIP based Instant Messaging System which includes message server that can store and manage instant messages. With this message server, messages could be exchanged legalness of user states. Furthermore, our system includes message waiting indication event package which provides useful informations about messages in the message server. And this system also includes the Caller Preference capabilities.

• Journal of KIISE:Information Networking
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• v.32 no.1
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• pp.51-59
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• 2005

In this paper, we propose and implement a hybrid-type video conference system using SIP protocol proposed in IEFT. This conference system, all signaling is controled by the server, while the media communication can be managed either by UAs or by the server. as a result, the complexity of its routing and user state management is reduced and it is applicable to the mobile environment of the ad-hoc models. The implemented server is scale enough to be used in a large conference because it only takes charge of signaling part. And also we see that UAs are only suitable in the small conference where less than ten people can join.

• Journal of KIISE:Information Networking
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• v.30 no.5
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• pp.621-630
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• 2003

In this paper, we implemented SIP protocol that supports IPv6 and differentiated call processing scheme for NGN(Next Regeneration Network). In NGN, SIP processes call signaling among various application services. A softswitch and SIP server must give priority to sensitive services such as Fax, network management and home networking that require a fast call setup time. Also, the support of IPv6 is needed under consideration of All-IP. We proposed differentiated call processing scheme. The differentiated call processing scheme supports differentiated call processing as priority of service class on call processing in SW server We defined three service classes and use the Flow Label field of the IPv6 header for setting service class. Through the performance analysis, we proved that it improves throughput for call message with the high priority. The result of performance analysis demonstrates that differentiated call processing scheme gives better performance for the service requiring a fast session establishment in NGN.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.161-161
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• 2004

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.6
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• pp.547-553
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• 2019

Presence server should process massive SIP subscription request messages and massive presence event notifications from presence resources in real time. Therefore multiple servers architecture is needed for presence service system. In this paper, an architecture of multiple servers presence service system using SIP based CCMP control messages for lowering presence server load level has been presented. In this system, each presence server exchanges current load status using CCMP control messages, and total system load according to variance of users number and amount of presence resources has been effectively distributed processed. The CCMP control messages has been optimally designed to control presence servers, and exchange procedures of these control messages between presence servers has been also presented and the performance of the proposed multiple servers presence service system has been analysed by experiments. The result shows that average presence subscription processing time reduced from 40.8% to 69.2% and average presence notification processing time reduced from 29.4% to 62.7%.

• Journal of the Korea Society of Computer and Information
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• v.14 no.9
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• pp.67-74
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• 2009

The presence informations of users of Instant Messaging System In SIP(Session Initiation Protocol) environment are obtained by presence server, and message waiting indication event package is used to provide various message informations stored in the message server. In this paper, I have proposed a new method in which Extended CPL(Call Processing Language) has been applied to presence service to provide various functions to the users. A user of Instant Messaging System subscribes presence information and CPL scripts which describe his requirements, and presence server executes CPL scripts when instant messaging service is subscribed and notifies presence informations. Several CPL operation tags are added, and therefore various services which combine presence service and call processing can be provided in this system. Furthermore a new method has been proposed in which message server and presence server correlate in Instant Messaging System. When changes of message status informations occur, message server send these informations to the presence server, and presence server provides both presence informations and message status informations in extended format. As this method can be a substitute for message waiting indication event package, the system operating efficiency can be increased. The performance of this proposed system is evaluated by experiments.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.176-179
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• 2003

The use of Multiparty Conference service based on SIP for VoIP provides is gradually magnified, and the work for continuous development and standardization on SIP is in the process of advancing. But, currently it is impossible for SIP to support identity discovery and distribution of each participant for multiparty conference. In this paper, we propose a SIP extension for guaranteeing security on the multiparty conference using SIP by adding new method and reconstructing header informations. With this, it is also possible to identify discovery and to distribute each participant using SIP extension when a call is established for closed multiparty conference.