• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8A
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• pp.928-936
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• 2004

This paper proposes simple and effective Contention Window (CW) adjusting algorithm to solve the fairness problem of the IEEE 802.11 under the Distributed Coordination Function (DCF). This adjusting algorithm can support variable packet length as well as both RTS/CTS access method and hidden nodes. Simulation results show that fairness problem can be very severe in the original MAC protocol of the wireless network. In case of implement our algorithm, fair sharing was enlarged prominently and the fairness sharing was improved about maximum 30%.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06d
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• pp.115-117
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• 2006

IEEE 802.11 표준은 채널 상태에 따라 다양한 전송 속도를 지원하며, 무선랜 환경에서 이러한 특성을 활용하는 연구들이 진행되어 왔다. 그러나, 모바일 애드 혹 네트워크 환경에서 다중전송속도를 활용하는 연구는 거의 이루어지지 않았다. 본 논문은 모바일 애드 혹 네트워크에서 동적으로 다중전송속도를 활용하여 채널 효율을 높이는 알고리즘을 제안한다. 제안 기법은 MAC 계층과 네트워크 계층 중간에 위치하며 각 계층에 독립적으로 동작한다. 라우팅 프로토콜에서 결정한 다음 홉에 더불어, 제안 기법은 더 빠른 전송 속도를 갖는 중계 경로를 탐색한다. 또한, 패킷의 크기에 따라 경쟁 부하를 고려하여 선택적으로 전송 경로를 변경한다. 모의 실험을 통한 성능 평가는 제안 기법의 우수한 성능을 입증한다.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10c
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• pp.532-534
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• 2000

IPv4(Internet Protocol version 4)의 차세대 버전인 IPv6는 기존 IPv4의 문제점인 주소부족 및 새로운 부가기능 등의 필요성 때문에 IETF(Internet Engineering Task Force)에서 IPv4를 대체하기 위해 개발한 프로토콜이다. 하지만 IPv4를 어느 한순간에 IPv6로 대체하는 것은 불가능하기 때문에 기존 IPv4와의 호환 및 연동을 위한 터널링 및 기타 여러 가지 transition mechanism들이 고려되고 있다. 이러한 mechanism들 중에서 최근 표준으로 발표된 NAT-PT(Network Address Translation $\square$ Protocol Translation)는 DNS-ALG (Domain Name System $\square$ Application Level Gateway)라는 개념을 도입하여 IPv4와 IPv6간의 양방향 주소변환 및 프로토콜 변환기능을 수행한다. 각각의 기능에서 주소 변환은 주소크기와 형식이 다른 IPv4와 Pv6간의 서로 상대 노드를 엑세스할 수 있도록 하고 프로토콜 변환은 다른 버전의 프로토콜을 사용하는 노드들이 상대노드가 보낸 패킷의 헤더정보를 이해할 수 있도록 한다. 그리고 이러한 기본적인 변환 외에 헤더정보의 정확한 전달을 위해서는 기존의 path MTU(Maximum Transgfer Unit) discovery 그리고 pseudo header checksum 등도 고려되어야 한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.6
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• pp.2234-2239
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• 2010

In this paper, the performance of ad-hoc wireless network protocols is analyzed under the vehicular communication environments. We estimate the throughput and delay of the protocols with packet sizes and various data traffics in expressways and metropolis by using QualNet simulator. It turns out that the performance of DSR protocol is better in expressways and the performance of AODV works well in metropolitan areas. Therefore, it is necessary that the proper protocols should be selected to provide the better performance according to the vehicular communication environments.

• Journal of Game and Entertainment
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• v.2 no.1
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• pp.8-16
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• 2006

The development of multicast communication services in the Internet is expected to lead a stable packet transfer even though On-Line Games generate heavy traffic. The Core Based Tree scheme among many multicast protocols is the most popular and suggested recently. However, CBT exhibits two major deficiencies traffic concentration or poor core placement problem. Thus, measuring the bottleneck link bandwidth along a path is important to understand the performance of multicast. We propose a method in which the core router's state is classified into SS(Steady State), NS(Normal State) and BS(Bottleneck State) according to the estimated link speed rate, and also the changeover of multicast routing scheme for traffic overload. In addition, we introduce Anycast routing tree, an efficient architecture for constructing shard multicast trees.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.23 no.6
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• pp.989-1000
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• 2013

Mobile devices use VPN solution to transfer information securely through open network in mobile office environment. In this paper, we propose Pre_Buffered mechanism that improves the throughput of IPSec VPN using low performance H/W crypto Token. Pre_Buffered method precompute key stream, store them in Buffer and use them in IPSec engine for IP packet processing. Moreover, Design, analysis, and experimental results prove the efficiency and feasibility of our proposed method.

• The Journal of the Korea Contents Association
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• v.5 no.2
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• pp.79-85
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• 2005

In order to handle client's requests while multiple servers seamlessly work in the web server cluster environment, it is vital to implement a router that execute a routing using TCP information and requested target content. The implemented package software measured packet volume that was generated from data generator, virtual server, and server 1, 2, 3, and could find out traffic distribution toward Server 1, 2, 3. As the result of the study shows, Round Robin Algorithm ensured definite traffic distribution, unless incoming data loads differ much. Although error levels were high in some partial cases, they were eventually alleviated by repeated tests for a longer time.

• Journal of Internet Computing and Services
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• v.2 no.3
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• pp.9-17
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• 2001

Ad-Hoc networks consist of a set of mobile hosts that communicate using wireless links, without the use of other communicate support facilities (such as base stations). The topology of an Ad-Hoc network changes due to the movement of mobile host. which may lead to sudden packet loss. Recently, a large amount of research has focused on the routing protocols needed in such an environment. but researches about Internet traffic performance analysis were unexhausted. Accordingly, we have simulated Ad-Hoc mobile network that using AODV routing protocol and Ad-Hoc mobile network topology size and node speed as simulation estimation-factor to analysis traffic performance. As the result of the simulation, we identify that TCP /Reno was more sensitive than TCP/Sack about node speed and a number of the node.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11C
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• pp.102-112
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• 2001

This paper analyzes Security Performance and Processing Performance to measure performance between nodes by using AH and ESP protocol. IPsec VPN provides application with security service implemented in IP Layer while traffic cost and packet processing time it increased by encryption, decryption and authentication in AH and ESP. We measured overall packet processing time and IPsec module processing time. The result of the efficiency test showed that the factors of influencing electrical transmission efficiency were the size of electrical transmission packets, codes used for tunnelling, authentication functions, CPU velocity of host7, and the embodiment of IPsec; for a high capacity traffic, IPsec transmission was not appropriate, because transmission velocity was delayed by more than ten times in comparison with Non-IPsec.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.6
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• pp.1610-1618
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• 1998

In this paper, we present the FB(Fair Buffering) mechanism for the efficient support of TCP traffic over UBR connections in the subnet ATM model. We show that both throughput and fairness may be improved with the FB mechanism. The FB mechanism is founded on the observation that the performance of TCP over UBR connections is optimal when the buffer space is allocated in proportion to the connection's bandwidth-delay product. We compare through simulation the performance of the existing drop-tail, EB(Equal Buffering) and the proposed FB buffer management schemes, with and without RR(Roung-Robin) scheduling, and demonstrate that the proposed FB mechanism is most effective when used in conjunction with the RR scheduling scheme.