• The Transactions of the Korea Information Processing Society
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• v.6 no.11S
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• pp.3340-3349
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• 1999

Supporting object group on distributed object system give merits such as load balancing, fault tolerance and high availability. In this paper, we describe a CORBA ORB that has been designed to support object group based on active replication. The ORB supports the operational model in which it uses the IIOP for communication between client and server and total ordered multicast protocol for consistency control among group members. And through extension of ORB, it provides functions required for support of object group. Since it provides transparency of object replication, the ORB is interoperable with the existing CORBA products. It make possible for existing server application to be easily extended to application supporting object group as adding interface functions which should be used for building applications is minimized. A prototype is implemented, and performance of the replicated object group is tested and compared with a single object invocation.

• Journal of Communications and Networks
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• v.8 no.4
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• pp.378-390
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• 2006

Many distributed applications build overlays on top of the Internet. Several unsolved issues at the network layer can explain this trend to implement network services such as multicast, mobility, and security at the application layer. On one hand, overlays creating basic topologies are usually limited in flexibility and scalability. On the other hand, overlays creating complex topologies require some form of application level addressing, routing, and naming mechanisms. Our aim is to design an efficient and robust addressing, routing, and naming infrastructure for these complex overlays. Our only assumption is that they are deployed over the Internet topology. Applications that use our middleware will be relieved from managing their own overlay topologies. Our infrastructure is based on the separation of the naming and the addressing planes and provides a convergence plane for the current heterogeneous Internet environment. To implement this property, we have designed a scalable distributed k-resilient name to address binding system. This paper describes the design of our overlay infrastructure and presents performance results concerning its routing scalability, its path inflation efficiency and its resilience to network dynamics.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6B
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• pp.433-442
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• 2012

We have proposed a solution to multicast services and an advanced quality of service (QoS) mechanism on a packet transport system (PTS) based on PBB-TE. The point-to-multipoint (PtMP) connection in the PBB-TE system have been realized by grouping point-to-point (PtP) PTL trunks and mapping a BSI onto the PtP PTL trunks using a multicast backbone destination address. To provide end-to-end QoS of the PtMP services, the hierarchical QoS scheme for backbone service instances and connection-oriented paths has been implemented in the PTS. For providing different capabilities for service selection and priority selection, the PTS offers to customers three basic types of the port-based, C-tagged, and S-tagged service interface defined by the IEEE 802.1ah. To offer to customers different capabilities of the layer 3 applications and services, moreover, an IP-flow service interface have been added. In order to evaluate traffic performance for PtMP services in the PTS, the PtMP throughputs for the link capacity of 1 Gbps at the four service interfaces were measured in the leaves of the ingress edge node, the transit node, and the egress edge node. The throughputs were about 96 % because the B-MAC overhead of 22 bytes occupies 4% of the 512-byte packet. The QoS performance is ability to guarantee an application or a user a required bandwidth, and could be evaluated by the accuracy of policing or shaping. The accuracy of the policing scheme and the accuracy of the shaping scheme were 99% and 99.3% respectively.

• Journal of Internet Computing and Services
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• v.3 no.2
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• pp.79-85
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• 2002

In open communication architecture, application systems consist of objects distributed in lots of computing nodes. To reduce complexity of development. and management of distributed software, to manage efficiently distributed objects and to provide realtime service, the mechanisms for object group management and communication are needed in distributed environment. In this paper we compose object groups and provide reliable group communication mechanism based on CORBA which can adopt a new service without lots of changes on existing system. Group consist of some subgroups that subgroup manager manages for improving the efficiency of group management and message ordering is kept by using sequencer, Communication method among groups uses multicast based on paint to point communication as well as IP multicast and we provide high performance by using selective retransmission of message through message history, We analyze the performance of the proposed mechanism through simulation in distributed environment.

• Journal of KIISE
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• v.42 no.11
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• pp.1441-1451
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• 2015

As one of the most spotlighted research areas, these days, the Internet of Things (IoT) aims to provide users with various services through many devices. Since there exist so many devices in IoT environments, it is inefficient to manually configure the domain name system (DNS) names of such devices. Thus, for IPv6-based IoT environments, this paper proposes a scheme called the DNS Name Autoconfiguration (DNSNA) that autoconfigures an IoT device's DNS name and manages it. In the procedure for generating and registering an IoT device's DNS name, the standard protocols of the Internet Engineering Task Force (IETF) are used. Since the proposed scheme resolves an IoT device's DNS name into an IPv6 address in unicast through a DNS server, it generates less traffic than multicast-based mDNS (Multicast DNS) which is a legacy DNS application for the DNS name service in the smart home. Thus, the proposed scheme is more appropriate in multi-hop IoT networks than mDNS. This paper explains the design of the proposed scheme and its service scenarios, such as smart home and smart road. It also explains the implementation and testing of the proposed scheme in the smart grid.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.12
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• pp.2852-2859
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• 1997

Video-On-Demand system provides electronic video rental services from remote video servers on a broadband communication networks. Most of proposed VOD systems are typically designed for one-to-one conncetion between a user and video server. Therefore, video server stream services to customers individually by allocating a dedicated transmission channel and a set of video server resources for each customer. However, it is inefficiency and wxpensive way when server support multiple users who access the same video stream with a dedicated video channel. Therefore, to achieve cost-effectiveness, batching have studied method that uses multicast communication to simultaneously service all users requesting the same video with a single video with a single video stream. However, the application of the multicast communication by batching detract from the VCR-like function and on-demand nature of the system. In this paepr, we propose a scheme that can support an interactive VCR for all user requesting the same video stream with batching. To reduce a server I/O and network bandwidth requirement, dynamic buffer is allocated to access node which has variable playout poit. Consequently, it makes possible interactive VCR operation as if customer uses true VOD system. Also, this scheme can just deliver a multicast stream without delay after an initial request or VCR action occurred. The policy can guarantee acceptable services to number of users at minimum cost.

• Journal of Satellite, Information and Communications
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• v.1 no.1
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• pp.40-47
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• 2006

The next-generation mobile communication system are required to provide high-data-rate and high quality transmission over hostile radio channels. Orthogonal Frequency Division Multiplexing(OFDM) technique regarded as a most promising solution in mobile environment. This paper considers the issue of efficient subcarrier allocation for OFDM system in multi-service application. Proposed algorithm can consider channel gain of each service and divide subchannel. Proposed method considers priority of service and divide more subchannels in high priority service. When proposed algorithm compares with existent algorithm, the convergence rate improves and the calculation amount is decreased.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.1
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• pp.74-79
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• 2006

In this paper, we present a technique for distributed media object live streaming using RMI and JMF. Then, we handle technique that simplify complex control of distributed objects using RMI and do one-to-many live streaming in network environment that do not support multicast using JMF. It can separate transmission and control to use RMI and JMF based on Java. Consequently the technique is available in development of multimedia service application that is independent to platform.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10e
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• pp.685-687
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• 2002

기존의 IPv4의 주소고갈 문제를 해결하기 위해 대두된 IPv6는 많은 연구들과 표준화가 이루어졌고, 현재는 IPv6를 활용화 하기 위해 IPv4에서의 IPv6로의 변환 및 순수 IPv6망 활용에 관한 연구가 이루어지고 있다. 이와 같은 배경에서 본 연구진은 IPv6의 활용을 위해 IPv6 멀티캐스트기반 고품질 화상회의 응용을 개발하였다. 추후, 본 응용은 순수 IPv6 망 상에서 다양한 조건으로 실험 및 활용되어 IPv6 망이 성공적으로 실용화 되는데 기여 할 수 있을 것으로 기대된다.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.1
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• pp.1-8
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• 1997

A wide class of networking application services, such as video teleconferencing, VOD, LAN bridging, and distributed data processing require multipoint communications. The essential component inteh network to achieve this is a multicast packet switch which is capable of packet replication and switching. In this paper, we propose an efficient mukticast addressing scheme using the smallest number of routing bits which is deterministic lower bound. The new scheme performs all point-to-multipoint connection in radix-2 tree ATM switch like banyan network. Also, we provide a simple radix-2 switch block diagram for achieving our algorithm. And we investigate several addressing schemes for implementing multicasting in radix-r tree ATM switch and evaluate several performance factors, such as complexity of the additional header bits, requirement of the internal speedup and complexity of the major hardware.