• Journal of KIISE:Information Networking
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• v.32 no.2
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• pp.215-219
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• 2005

Generally, the mobile nodes in MANET have the limited power capacity available for actual communications. Thus, the power management is very important for packet routing or forwarding. Although MTPR, MBCR and MMBCR are proposed to treat the problem of power consumption, there have been few researches resolving the link breakdown that is occurred by the power exhaustion during transmission. In this sense, the reliable scheme should be required to ensure the routing connectivity. In this paper, we propose three schemes to enforce the routing connectivity. If the signal strength is dropped below a signal threshold, the candidate route is previously selected to prepare the link breakdown. Also, on multi-channel, we propose the lifetime increment scheme of a node that it manage its available power to the needed power of a new link. The simulation results show the enforcement of the link connectivity and the performance improvements of the delay time through the effective connection management.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.2
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• pp.1070-1088
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• 2017

Recently, the applications of Internet of Things (IoTs) are growing rapidly. Wireless Sensor Network (WSN) becomes an emerging technology to provide the low power wireless connectivity for IoTs. The IPv6 over low-power wireless personal area networks (6LoWPAN) has been proposed by IETF, which gives each WSN device an IPv6 address to connect with the Internet. The transmission congestion in IoTs could be a problem when a large numbers of sensors are deployed in the field. Therefore, it is important to consider whether the WSN devices have be completely integrated into the Internet with proper quality of service (QoS) requirements. The Software Defined Network (SDN) is a new architecture of network decoupling the data and control planes, and using the logical centralized control to manage the forwarding issues in large-scale networks. In this research, the SDN-based 6LoWPAN Border Router (6LBR) is proposed to integrate the transmission from WSNs to Internet. The proposed SDN-based 6LBR communicating between WSNs and the Internet will bring forward the requirements of end-to-end QoS with bandwidth guarantee. Based on our experimental results, we have observed that the selected 6LoWPAN traffic flows achieve lower packet loss rate in the Internet. Therefore, the 6LoWPAN traffic flows classified by SDN-based 6LBR can be reserved for the required bandwidth in the Internet to meet the QoS requirements.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.12
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• pp.6214-6242
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• 2019

Routing in mobile ad hoc networks is performed in a distributed fashion where each node acts as host and router, such that it forwards incoming packets for others without relying on a dedicated router. Nodes are mostly resource constraint and the users are usually inclined to conserve their resources and exhibit selfish behaviour by not contributing in the routing process. The trust and reputation models have been proposed to motivate selfish nodes for cooperation in the packet forwarding process. Nodes having bad trust or reputation are detected and secluded from the network, eventually. However, due to the lack of proper identity management and use of non-persistent identities in ad hoc networks, malicious nodes can pose various threats to these methods. For example, a malicious node can discard the bad reputed identity and enter into the system with another identity afresh, called whitewashing. Similarly, a malicious node may create more than one identity, called Sybil attack, for self-promotion, defame other nodes, and broadcast fake recommendations in the network. These identity-based attacks disrupt the overall detection of the reputation systems. In this paper, we propose a reputation-based scheme that detects selfish nodes and deters identity attacks. We address the issue in such a way that, for normal selfish nodes, it will become no longer advantageous to carry out a whitewash. Sybil attackers are also discouraged (i.e., on a single battery, they may create fewer identities). We design and analyse our rationale via game theory and evaluate our proposed reputation system using NS-2 simulator. The results obtained from the simulation demonstrate that our proposed technique considerably diminishes the throughput and utility of selfish nodes with a single identity and selfish nodes with multiple identities when compared to the benchmark scheme.

• Journal of KIISE:Information Networking
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• v.30 no.2
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• pp.252-259
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• 2003

In the case of link congestion, most of the existing ad-hoc routing protocols like AODV and DSR do not try to discover a new route if there is no change in the network topology. Hence, with low mobility, traffic may get concentrated on some specific nodes. Since mobile devices have low battery power and low computing capability, traffic concentration on a specific node is not a desirable phenomenon. Therefore, in this paper, we propose a new protocol called SLAP (Simple Load-balancing Ad-hoc routing Protocol) which resolves the traffic concentration problem by letting each node check its own load situation and give up its role as a packet forwarder gracefully in the case of high traffic load. We compare the performance of SLAP with that of AODV and DSR in terms of the forwarding traffic distribution.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.3B
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• pp.437-445
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• 2000

More advanced and demanding applications, like videoconferencing, video on demand. distributed computing etc., have been devised thanks to the availability of enhanced network feature. Network technologies need to be enhanced to support these applications and to cope with the increasing number of users. Increasing the availability of network resources is just not enough to achieve this goal; scalable network architecture. increased packet forwarding capabilities, a wider range of services are all additional requirements. MOLS (multiprotocol label Switching) is one of the new networking techniques under standardization in the scientific community. In this paper, we analyze the performance of label switching in ATM networks. Simulation tests were performed. In this simulation, we set a simple network configuration and used internet traffic traces from NLANR as input traffic sources. The simulation results and analysis will be helpful in utilizing the functions of ATM switching and IP routing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5B
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• pp.344-355
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• 2008

In this paper, we are dealing with the problems of performance evaluation of Differentiated Services(DiffServ) networks. For successful performance evaluation, the ability to accurately represent "real" traffic on the network by suitable traffic models is an essential ingredient. Many research results on the nature of real traffic measurements demonstrated LRD(long-range dependence) property for the Internet traffic including Web, TELNET, and P2P traffic. The LRD can be effectively represented by self-similarity. In this paper, we design and implement self-similar traffic generator using the aggregated On/Off source model, based on the analysis of the On-Off source model, FFT-FGN(Fast Fourier Transform-Fractional Gaussian Noise) model, and RMD(Random Midpoint Displacement) model. We confirmed the self-similarity of our generated traffic by checking the packet inter-arrival time of TCPdump data. Further we applied the implemented traffic generator to the performance evaluation of DiffServ networks and observed the effect of performance to the a value of the On/Off model, and performance of EF/BE class traffic by CBQ.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.538-541
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• 2006

Recently researches of P2P media streaming have been actively published, but the research what kind of P2P overlay networks are better to delivering media data has not been attended. This paper designs a P2P streaming media system model. In this system, we constructs a Half-Structure P2P overlay protocol based on node's capability as the infrastructure of streaming application, which utilizes the heterogeneity of the nodes to maintain topology, presents a active contents diffusing algorithm and Two-stage search algorithm, make it possible for nodes in P2P system to collect information according their capacity and reduces the number of forwarding packet compared with flooding. Also, we give an optimal scheme to scheduling media data.

• KIISE Transactions on Computing Practices
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• v.21 no.11
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• pp.727-732
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• 2015

These days, many researchers are working on Future Internet and a new networking paradigm called Software Defined Networking draws a great attention. In this paper, we redefine Software Defined Networking as Service Defined Networking which means that packets are categorized according to types of services. By using Service Defined Networking, we are not only dealing with the way to utilize the network resources efficiently but we also propose an algorithm to minimize the waiting time for packets to be delivered. This proposed algorithm can solve the delay problem, one of the most significant problems caused by network congestion. Also, since we are adopting Service Defined Networking, network resource utilization can be improved compared to the existing network.

• Journal of KIISE:Information Networking
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• v.36 no.3
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• pp.222-230
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• 2009

A sensor network is an important element of the ubiquitous and it consists of sensor fields that contain sensor nodes and sink nodes that collect data from sensor nodes. Since each sensor node has limited resources, one of the important issues covered in the past sensor network studies has been maximizing the usage of limited energy to extend network lifetime. However, most studies have only considered fixed sink nodes, which created various problems for cases with multiple mobile sink nodes. Accordingly, while maintaining routes to mobile sink nodes, this study aims to deploy the hybrid communication mode that combines single and multi-hop modes for intra-cluster and inter-cluster transmission to resolve the problem of failed data transmission to mobile sink nodes caused by disconnected routes. Furthermore, a 2-level hierarchical routing protocol was used to reduce the number of sensor nodes participating in data transmission, and cross-shape trajectory forwarding was employed in packet transmission to provide an efficient data dissemination method.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.5
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• pp.83-91
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• 2008

IISO/IEC 9594-8 defines the public key framework and attribute certificate framework. Attribute certificate framework deals with privilege management infrastructure(PMI). In PMI, for privilege management using attribute certificates, role assignment certificates and role specification certificates are used to assign and specify privileges independently. Role specification certificates includes privilege specifications and the details far privilege management of network environments. Privilege management of unreliable network environment tries to enhance the reliability and efficiency of privilege information transmission forwarding over unreliable routes in the presence of potentially faulty nodes and edges. Each node forms a role specification tree based on role specification relationship data collected from the network. In this paper privilege management cost with the role specification certificates tree structure is evaluated trying to reduce the overhead incurred by role creation and modification of privileges. The multicasting of packets are used for scalability. We establish management cost model taking into account the packet loss and node reliability which continuously join and leave for network. We present quantitative results which demonstrate the effectiveness of the proposed privilege management scheme.