• Journal of Information Processing Systems
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• v.6 no.2
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• pp.129-146
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• 2010

The trend of Next Generation Networks' (NGN) evolution is towards providing multiple and multimedia services to users through ubiquitous networks. The aim of IP Multimedia Subsystem (IMS) is to integrate mobile communication networks and computer networks. The IMS plays an important role in NGN services, which can be achieved by heterogeneous networks and different access technologies. IMS can be used to manage all service related issues such as Quality of Service (QoS), Charging, Access Control, User and Services Management. Nowadays, internet technology is changing with each passing day. New technologies yield new impact to IMS. In this paper, we perform a survey of IMS and discuss the different impacts of new technologies on IMS such as P2P, SCIM, Web Service and its security issues.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.9
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• pp.2285-2301
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• 2012

Peer-to-Peer (P2P) networks are becoming more and more popular in video content delivery services, such as Video on Demand (VoD). Scalability feature of P2P allows a higher number of simultaneous users at a given server load and bandwidth to use stream service. However, the quality of service (QoS) in these networks is difficult to be guaranteed because of the free-riding problem that nodes download the recourses while never uploading recourses, which degrades the performance of P2P VoD networks. In this paper, a distributed trust model is designed to reduce node's free-riding phenomenon in P2P VoD networks. In this model, the P2P network is abstracted to be a super node hierarchical structure to monitor the reputation of nodes. In order to calculate the reputation of nodes, the Hidden Markov Model (HMM) is introduced in this paper. Besides, a distinction algorithm is proposed to distinguish the free-riders and malicious nodes. The free-riders are the nodes which have a low frequency to free-ride. And the malicious nodes have a high frequency to free-ride. The distinction algorithm takes different measures to response to the request of these two kinds of free-riders. The simulation results demonstrate that this proposed trust model can improve QoS effectively in P2P VoD networks.

• Journal of the Korea Society for Simulation
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• v.16 no.4
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• pp.77-86
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• 2007

Web services are considered as the critical component in the business plans of corporations as they offers the potential for creating highly dynamic and versatile distributed applications that span across business boundaries. Web Service Orchestration studies composition of already-existing web services to create new value-added services. The composite web services could be executed in a centralized or peer-to-peer(P2P) orchestration model. Compared with centralized-orchestration model, the P2P-based orchestration model provides better scalability, reliability, and performance for the overall services. However, recent P2P-orchestration solutions have limitation in supporting complex workflow patterns. Therefore, they could not effectively handle sophisticated business workflow, which contains complex workflow patterns. In this paper, we propose the WORKGLOW system, which can deal with complex workflow patterns while it is able to perform composite services in P2P orchestration manner. Comparing with centralized orchestration systems, the WORKGLOW brings up more business logic advantages, better performance, and higher flexibility with only a little overhead.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.4
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• pp.1-7
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• 2015

Until now, face to face coaching has been applied almost for completing the goal in various field. Face to face coaching is difficult always to reach each other anywhere, anytime due to the availability of internet and mobile devices. Recently, e-coaching is attempted to expend. But current e-coaching is supporting the secondary role for face to face coaching. E-coaching system has many benefits to use advancement technologies in internet. Therefore, the development of e-coaching system based on horizontal relationships between coach and coachee needs to communication anytime and anywhere in Internet. Usually previous online coaching systems have four types of interactions i.e. electronic mail, video chat, text chat, phone call. Most of the e-coaching approaches are easy to access and provide communication synchronous; video chat is an excellent visibility, whereas e-mail is asynchronous and document-centric. In this paper, we design and implement the integration e-coaching system based on synchronous and asynchronous. This system provides the asynchronous coaching offered by way of e-mail, and the synchronous coaching used P2P (Peer to Peer) video chat and text group chat. This system allows simultaneously asynchronous and synchronous coaching, and supports individual and group communication for periodical or informal coaching.

• Journal of Industrial Convergence
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• v.20 no.7
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• pp.89-96
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• 2022

This study conducted to investigate the effects of Peer-Assisted Learning(PAL) applied to nursing education on self-directed learning ability, academic self-efficacy, and academic achievement of nursing students. The research design was a pre-post-post design with an inequality control group, and a total of 229 students from G University who agreed to participate in the study were included. After the completion of regular classes, the experimental group(N=117) was given a PAL program at least once a week for 10 weeks, and the control group(N=112) was given individual self-learning for 10 weeks. The collected data were analyzed using descriptive statistics, X2-test, and independent t-test using SPSS/WIN 21.0. As a result, self-directed learning ability(t=6.50, p<.001), academic self-efficacy(t=2.01, p=.046), and academic achievement(t=4.98, p<.001) were higher in the experimental group than in the control group. As the positive effect of peer learning on nursing students was confirmed through the results of this study, it can be used as useful basic data when designing extracurricular activities for nursing education.

• The Journal of the Korea Contents Association
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• v.14 no.10
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• pp.20-31
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• 2014

Recently, cache sharing methods have been studied in order to effectively reply to user requests in mobile P2P networks. In this paper, we propose a cache sharing scheme based on a cluster considering the peer connectivity in mobile P2P networks. The proposed scheme shares caches by making a cluster that consists of peers preserving the connectivity among them for a long time. The proposed scheme reduces data duplication to efficiently use the cache space in a cluster. The cache space is divided into two parts with a data cache and a temporary cache for a cache space. It is possible to reduce the delay time when the cluster topology is changed or the cache data is replaced utilizing a temporary cache. The proposed scheme checks the caches of peers in a route to a cluster header and the caches of one-hop peers in order to reduce the communication cost. It is shown through performance evaluation that the proposed scheme outperforms the existing schemes.

• Journal of the Korea Society of Computer and Information
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• v.17 no.12
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• pp.111-120
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• 2012

As the P2P System is a distributed system that shares resources of nodes that participate in the system, all the nodes serve as a role of server and client. Currently, although systematic, structured P2P systems such as Chord, Pastry, and Tapestry were suggested based on the distributed hash table, these systems are limited to $log_2N$ for performance efficiency. For this enhanced performance efficiency limited, the article herein suggests group routing algorithm. The suggested algorithm is a node-to-group routing algorithm which divides circular address space into groups and uses a concept of pointer representing each group, which is an algorithm where routing is performed based on pointer. To evaluate algorithm performance, a comparative analysis was conducted on average hops, routing table size, and delayed transmission for chord and routing, a signature algorithm in P2P systems. Therefore, enhanced performance is verified for comparative items from the simulation results.

• Journal of KIISE:Information Networking
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• v.34 no.2
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• pp.88-99
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• 2007

P2P systems are distributed data sharing systems, and each node in them plays the role of client as well as server. There are several studies using Distributed Hash Table, such as Chord, CAN, Tapestry, Pastry, but these systems don't consider the physical latency, therefore they have a weakness of difficulty to guarantee stable performance. To improve this problem, we present the TP2P system. This system is a self-organizing hierarchical overlay system and it uses Chord routing mechanism for lookup data. This system is organized by several subnets, each subnet is organized by physically close nodes, and global network organized by all nodes. In each subnet, one node finds a data, it saves in a node in the subnet, therefore it has higher probability to reduce physical lookup latency than Chord system. And each node has global information of some nodes in its subnet, and it is used to lookup data, therefore the number of hops decrease about 25% as well as the physical lookup latecy are reduced.

• Journal of information and communication convergence engineering
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• v.2 no.3
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• pp.182-186
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• 2004

When most of existing instant messengers log on server, they transmit to sever in encoding password to RC5. but RC5 don't be secured because it has been known many of password cracking tools. Also, messengers don't have any protection on the transmitted information with communicating two hosts since loging on, endangering the privacy of the user. As a counter measure, messengers need to provide security service including message encryption. In this paper, we designed a key exchange method of password representing fast, effective and high security degree, using ECC(Elliptic Curve Cryptography) that being known the very stronger than another public key cryptography with same key size. To effectively improve data transmission and its security using IPSec protocol between users, tunnel mode is introduced. Tunnel mode transmits Host-to-Host data through virtual pipelines on the Internet.

• Journal of Digital Contents Society
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• v.14 no.1
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• pp.89-95
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• 2013

Many peer-to-peer (p2p) systems have been studied in distributed, ubiquitous computing environments. Distributed hash table (DHT)-based p2p systems can improve load-balancing even though locality utilization and user mobility are not guaranteed. We propose a mobile locality-based hierarchical p2p overlay network (MLH-Net) to address locality problems without any other services. MLH-Net utilizes mobility features in a mobile environment. MLH-Net is constructed as two layers, an upper layer formed with super-nodes and a lower layer formed with normal-nodes. The simulation results demonstrate that MLH-Net can decrease discovery routing hops by 13% compared with JXTA and 69% compared with Chord. It can decrease the discovery routing distance by 17% compared with JXTA and 83% compared with Chord depending on the environment.