• The KIPS Transactions:PartC
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• v.11C no.3
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• pp.327-336
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• 2004

There is a need for content providers and operators to control the usage of downloaded digital contents. Digital Rights Management(DRM) is the means to control the usage of the digital contents once it has been downloaded. Therefore, appropriate security mechanism is required. The mobile DRM system Is same as the general DRM system. We use encryption technology to package digital contents. In case of Mobile DRM system, secure distribution and secure keeping of packaging encryption key is important. In this paper, we design and implement DRM system on the Mobile Environments following on OMA(Open Mobile Alliance) DRM Model. We considered being a secure DRM system to contain appropriate security solution.

• Journal of KIISE:Computing Practices and Letters
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• v.9 no.5
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• pp.578-587
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• 2003

The DSTM (Dual Stack Transition Mechanism), one of tunneling mechanism, is considered as the best solution in IPv4/IPv6 transition recently. The DSTM provides a method to assure IPv4/v6 connectivity based on 4over6 (IPv4-over-IPv6) tunneling and temporal allocation of a global IPv4 address to a host requiring such communication. A TEP (Tunnel End Point) operates as a border router between IPv6 domain and IPv4 Internet, which performs encapsulation and decapsulation of 4over6 tunneling packets to assure hi-directional forwarding between both networks. In this paper, we analyze basic standards of the IPv6 protocol. And, we design and implement a DSTM TEP daemon block. The TEP daemon analyzes a fevers tunneling packet that is forwarded by the DSTM node, establishes the TEP's 4over6 interface, and supplies communication between a DSTM and a IPv4-only node. Finally, we construct a DSTM testbed and measure performance of the DSTM TEP. Our observation results show that performance of TEP supports the DSTM service.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.1B
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• pp.7-20
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• 2011

Recently, Proxy Mobile IPv6(PMIPv6) networks have been studied as the mobility management protocol to effectively use limited wireless resources. And the multicasting, which is core technology of the Internet broadcast system such as mobile IPTV, has been discussed mainly based on PMIPv6 network. However, multicasting based on PMIPv6 network causes disconnection of services because it does not solve problems of packet loss during binding and group joining procedure. Hence, we propose a seamless multicast scheme which prevents packet loss in PMIPv6 networks. The proposed scheme achieves lower latency than the existing scheme because it combines binding and group joining procedure, a1so it does not cause about packet losses due to performing buffering. We proved the performance using the simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.3
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• pp.258-267
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• 2013

Recently, Proxy Mobile IPv6(PMIPv6) networks have been drawing attention as the mobility management protocol that uses limited wireless resources effectively. And the multicast, which is a core technology of the Internet broadcast system such as mobile IPTV, has been widely discussed mainly based on PMIPv6 network. However, PMIPv6-based multicast cannot support the global mobility directly between different PMIPv6 domains because PMIPv6 is basically designed for local mobility in single PMIPv6 domain. Moreover, PMIPv6-based multicast causes the disconnection of services because it does not solve the packet loss problem during binding and group joining procedure. In this paper, we propose a global mobility scheme that supports the seamless multicast service in PMIPv6 networks. The proposed scheme supports the global mobility due to the addition of extra signalling messages between LMAs. Also, it achieves low latency because it performs fast binding and group joining procedure. We present the simulation results which show that the proposed scheme achieves the global mobility with low latency through the NS-2 simulation.

• Journal of KIISE:Computer Systems and Theory
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• v.36 no.5
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• pp.351-359
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• 2009

Recently with increase of data in the Internet, platform technologies that can process huge data effectively such as Google platform and Hadoop are regarded as worthy of notice. In this kind of platform, there exist network I/O overheads to send task outputs due to the MapReduce operation which is a programming model to support parallel computation in the large cluster system. In this paper, we suggest applying of TIPC (Transparent Inter-Process Communication) protocol for reducing network I/O overheads and increasing network performance in the distributed computing environments. TIPC has a lightweight protocol stack and it spends relatively less CPU time than TCP because of its simple connection establishment and logical addressing. In this paper, we analyze main features of the Hadoop-based distributed computing system, and we build an experimental model which can be used for experiments to compare the performance of various protocols. In the experimental result, TIPC has a higher bandwidth and lower CPU overheads than other protocols.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.12B
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• pp.1656-1664
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• 2001

When a packet loss occurs in a communication network operating a TCP protocol, the TCP protocol regards it that the loss has resulted from network congestion. Then the TCP protocol performs congestion control. When it is applied to the wireless network having quite a high BER characteristics, the performance of TCP protocol is degraded very much. In this paper, we propose an Explicit Error Notification(EEN) algorithm to improve the performance of the wireless TCP When a packet loss occurs in the wireless network, the TCP receiver decodes the TCP segment sequence number and the address of the TCP sender and receiver, and then informs the TCP sender of the error in wireless network by sending a NACK. It is to distinguish packets in error from losses of network congestion. In this paper, the performance of the proposed EEN algorithm is analyzed and simulated. In fact, as more errors are corrected, the proposed algorithm shows a larger improvements in performance.

• Journal of KIISE:Information Networking
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• v.32 no.6
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• pp.723-731
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• 2005

Wide spread deployment of infrastructure WLANs has made Wi Fi an integral part of today's Internet access technology. Despite its crucial role in affecting end to end performance, past research has focused on MAC protocol enhancement, analysis and simulation based performance evaluation without sufficient consideration for modeling inaccuracies stemming from inter layer dependencies, including physical layer diversity, that significantly impact performance. We take a fresh look at IEEE 802.11 WLANs, and using experiment, simulation, and analysis demonstrate its surprisingly agile performance traits. Contention based MAC throughput degrades gracefully under congested conditions, enabled by physical layer channel diversity that reduces the effective level of MAC contention. In contrast, fairness and jitter significantly degrade at a critical offered load. This duality obviates the need for link layer flow control for throughput improvement but necessitates traffic control for fairness and QoS. We use experimentation and simulation in a complementary fashion, pointing out performance characteristics where they agree and differ.

• Journal of KIISE:Information Networking
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• v.32 no.6
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• pp.687-695
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• 2005

With increasing demand of using mobile Internet, HMIPv6 is proposed by IETF to reduce location management traffics due to micro mobility and to provide IP-based movement. A paging mechanism combined with HMIPv6 can reduce the signaling traffics of a mobile node. We propose a dynamic paging mechanism in HMIPv6 which decides an optimal paging area for each mobile node by considering its characteristics. Total costs of a static paging mechanism and a dynamic paging mechanism are analyzed by mathematical formulas. As a result, we proved that the dynamic paging mechanism reduced total signal traffic costs more than a static paging mechanism.

• Journal of KIISE:Information Networking
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• v.29 no.6
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• pp.685-695
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• 2002

Recently, there has been increasingly demand for connecting a embedded device to the Internet. Jini technology is interested in automatically composing a distributed network with devices But, there are some problems that the device needs high hardware requirements to adopt Jini technology for supporting Jini-enabled services. In this paper, we focused on design and implementation of surrogate system that supports non-Java devices in Jini networks. This system and protocol are implemented in Java language. The surrogate system delegates Discovery and Join processing to support a Jini service in connected networks. A Jini client can use service of the device through the surrogate system. We tested a Jini sample program to verify the implemented surrogate system. In the test result, we showed that the Jini client can use functionalities and operations of the non-Java device through the surrogate system.

• Journal of Information Management
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• v.38 no.1
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• pp.141-160
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• 2007

Many contents produced and provided as development of information technology on the internet. Especially discussion that collecting and storing of digital information resources, is expanded as growing dependence on academic information of research workers. Open Access is a new paradigm of information distribution that is opposite concept of high price distribution academic information. It is an OAI system that is intended to collect and automate open access data in good order. This paper constructs stOAI based on OAI that is a science and technology information providing system. This system provides international academic journal free of charge that collect and store through OAI protocol in OA(Open Access) of yesKISTI(science and technology information portal service). Also, It provides automate and centralize science technology information, that KISTI has, to external institution as a standard type.