• Journal of Internet Computing and Services
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• v.9 no.4
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• pp.21-27
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• 2008

TCP receivers deliver ACK packets to senders for reliable end-to-end transfer. When ACK packets are not transferred properly because of network congestion, the performance of TCP degrades. This paper proposes a reverse congestion warning mechanism and a congestion handling mechanism in heterogeneous networks with heavy background traffic in the backward direction. Help from TCP receivers or hardware such as routers and gateways other than the ACK packets themselves is not necessary. TCP senders compare the arrival intervals of ACK data passed from receivers and the difference in t imestamp values echoed by receivers. According to the simulation results using the NS-2 network simulator, the proposed scheme shows a performance elevation of 20% greater than Reno, 150% greater than New Reno, and 450% greater than Westwood, respectively, under heterogeneous networks and that the error rate of the radio link is 1% when the backward network is congested.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.1B
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• pp.45-54
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• 2003

In the Protocol-Independent Multicast Sparse Mode(PIM-SM), we need a careful selection scheme for the Rendezvous Point(RP) which influences much on the QoS due to the delay among multicast group members and packet loss The QoS based RP selection schemes choose RPs which satisfy the restriction conditions such as bandwidth, delay, and other QoS parameters In this paper, we propose a new RP selection scheme which is a variation of the group-based RP selection scheme The new algorithm, MCT(Maximum Cross Tree), is implemented by taking advantages of the topology-based selection scheme and the group-based selection scheme as well In order to verify the proposed algorithm, we first measure the multicast traffic data of the Virtual Conference System implemented on the IPv6 network via KOREN, then expand the results to two types of network models and analyze the performance by computer simulation.

• Journal of the Korea Society for Simulation
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• v.28 no.2
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• pp.97-105
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• 2019

The tactical mobile ad-hoc network(MANET) consists of distributed autonomous networks between individual ground nodes, which is effective in terms of network survivability and flexibility. However, due to constraints such as limited power, terrain, and mobility, frequent link disconnection and shadow area may occur in communication. On the other hand, the satellite network has the advantage of providing a wide-area wireless link overcoming terrain and mobility, but has limited bandwidth and high-latency characteristic. In the future battlefield, an integrated network architecture for interworking multi-layer networks through a heterogeneous network gateway (HNG) is required to overcome the limitations of the existing individual networks and increase reliability and efficiency of communication. In this paper, we propose a new HNG architecture and detailed algorithm that integrates satellite network and the tactical MANET and enables reliable data transfer based on flow characteristics of traffic. The simulations validated the proposed architecture using Riverbed Modeler, a network-level simulator.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.331-337
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• 2014

Paradigm shift to cloud computing has increased the importance of security. Even though public cloud computing providers such as Amazon, already provides security related service like firewall and identity management services, it is not suitable to protect data in cloud environments. Because in public cloud computing environments do not allow to use client's own security solution nor equipments. In this environments, user are supposed to do something to enhance security by their hands, so the needs of visualized security management arises. To implement visualized security management, developing near realtime data handling & packet classification mechanisms are crucial. The key technical challenges in packet classification is how to classify packet in the manner of unsupervised way without human interactions. To achieve the goal, this paper presents automated packet classification mechanism based on naive-bayesian and packet Chunking techniques, which can identify signature and does machine learning by itself without human intervention.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.4
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• pp.562-570
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• 2022

The supply expansion of 5G services and personal smart devices has caused the sharp increase of data traffic and the demand of various services. Again, these facts have resulted in the huge demand of network bandwidth. However, existing network technologies using electronic signal have reached the limit to accommodate the demand. Therefore, in order to accept this request, optical internet has been studied actively. However, optical internet still has a lot of problems to solve, and among these barriers a very urgent issue is to develop QoS technologies. Hence, in order to achieve service differentiation between classes in optical internet, especially in OBS network, a new QoS method automatically tuning the size of data bursts is proposed in this article. Especially, the algorithm suggested in this article is based on fiber delay line.

• KNOM Review
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• v.22 no.1
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• pp.42-51
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• 2019

Recently, the amount of internet traffic is increasing due to the increase in speed and capacity of the network environment, and protocol data is increasing due to mobile, IoT, application, and malicious behavior. Most of these private protocols are unknown in structure. For efficient network management and security, analysis of the structure of private protocols must be performed. Many protocol reverse engineering methodologies have been proposed for this purpose, but there are disadvantages to applying them. In this paper, we propose a methodology for inferring a detailed protocol structure based on network trace analysis by hierarchically combining CSP (Contiguous Sequential Pattern) and SP (Sequential Pattern) Algorithm. The proposed methodology is designed and implemented in a way that improves the preceeding study, A²PRE, We describe performance index for comparing methodologies and demonstrate the superiority of the proposed methodology through the example of HTTP, DNS protocol.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.2
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• pp.40-49
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• 2015

PicoCast is a recently proposed short-range wireless communications technology that supports both low rate sensor/control data and high speed data such as voice and video traffic in the personal space, defined by the user-centric space of radius tens of meters, with one unified protocol. When the users are in the same area, personal spaces defined by each user may overlap. Since these PicoCast piconets may simultaneously operate, mutual interference is unavoidable. It is necessary to investigate the effect of mutual interference on data transmission and to conduct research on minimizing the interference among PicoCast devices. In this paper we analyze the effect of mutual interference between PicoCast piconets based on data throughput using OPNET network simulator. We have implemented the PicoCast protocol and measured the average throughput and packet loss rate.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.4
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• pp.121-126
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• 2009

Video poxy server which is located near clients can store the frequently requested video data in storage space in order to minimize initial latency and network traffic significantly. However, due to the limited storage space in video proxy server, an appropriate deletion algorithm is needed to remove the old video data which is not serviced for a long time. Thus, we propose an efficient video data deletion algorithm for video proxy server. The proposed deletion algorithm removes the video which has the lowest request possibility based on the user access patterns. In our algorithm, we arrange the videos which are stored in video proxy server according to the requested time sequence and then, select the video which has the oldest requested time. The selected video is partially removed in order to free up storage space in video poky server. The simulation results show that the proposed algorithm performs better than other algorithms in terms of the block hit rate and the number of block deletion.

• Journal of Advanced Navigation Technology
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• v.16 no.1
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• pp.96-102
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• 2012

The goal of mobile internet system is to provide a high-data-rate, low-latency and optimized packet radio access technology supporting flexible bandwidth deployments. Therefore, network architecture is designed with the goal to support packet-switched traffic with seamless mobility, quality of service and minimal latency. An important requirement for the mobile internet system is improved cell-edge BER performance and data throughput. This is to provide some level of service consistency in terms of geographical coverage as well as in terms of available data throughput within the communication coverage area. In a cellular system, however, the signal to interference plus noise power ratio gap between cell-center and cell-edge users can be of the order of 20 [dB]. The disparity can be even higher in a communication coverage limited cellular system. This leads to vastly lower data throughputs for the cell-edge users relative to cell-center users creating a large QoS gap. This paper proposes a analytical approach that tries to reduce inter-cell interference, and shows the SIR and BER performance according to the OFDM system parameters in mobile Internet environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9A
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• pp.837-843
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• 2006

IEEE802.15.3 and IEEE802.15.4 have defined the hybrid MAC protocols based on TDMA and CSMA where a multi-frame TDMA structure is employed so that multiple data frames can be transmitted within one timeslot to guarantee minimum delay bounds of isochroous traffic. However, TDMA has an intrinsic problem that cannot dynamically allocate optimal length of timeslot to each station. Therefore the idle timeslot can be produced by stations when each transmission queue is instantaneously empty during its timeslot, which would waste lots of timeslots especially in the multi-frame TDMA systems. In this paper, we propose a more flexible multiple-access scheme for the multi-frame TDMA system based on the concept of virtual slot which is accessible by every station with the highest priority for slot owner and lower priority for other stations. Finally, our simulation results from various environments show that proposed scheme can achieve magnitude improvement of total system throughput and average message delay by maximizing channel utilization.