• Title/Summary/Keyword: 혼잡도

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Performance improvement of TCP Reno congestion control algorithm using end-to-end estimation of forward/backward delay variation (종단간 순방향/역방향 전송 지연에 따른 TCP Reno 혼잡제어 알고리즘 성능향상)

  • Han, Kyu-Hyeong;Kim, Eun-Gi
    • Proceedings of the Korea Information Processing Society Conference
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    • 2005.11a
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    • pp.1295-1298
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    • 2005
  • 기존 TCP Reno 의 혼잡 제어는 트래픽에 수동적으로 동작하는 방법으로서 혼잡이 이미 발생한 상태에서 동작하게 되므로 발생 시점의 라우터 버퍼는 이미 최대치에 도달해 있게 된다. 따라서 이후에 도착하는 모든 패킷은 폐기되므로 이 패킷들을 전송한 모든 송신원은 거의 동시에 윈도우 크기를 줄이는 Slow-start 단계에 들어가게 되어 일시적으로 링크 사용률이 떨어지는 전역 동기화(global synchronization)가 발생하게 된다. 이러한 문제를 해결하기 위해서는 네트워크의 혼잡이 발생하기 전에 능동적으로 대처하는 방안이 필요하다. 본 논문에서는 새로운 RTT 계산 알고리즘인 순방향/역방향 전송지연 알고리즘을 이용하여 네트워크의 혼잡을 미리 예측하고 네트워크 혼잡에 능동적으로 대처할 수 있는 새로운 알고리즘을 제안한다. 본 논문에서는 리눅스(Linux) 커널(Kernel)의 TCP Reno 의 흐름제어 및 혼잡제어를 수정하여 네트워크 혼잡에 능동적으로 대처 할 수 있는 새로운 TCP Reno 를 설계, 구현하였다.

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Design and Implementation of the system for Measuring Congestion of Road using Region Information (영역 정보를 이용한 교통 혼잡도 측정 시스템의 설계 및 구현)

  • 최병걸;안철웅;김승호
    • Proceedings of the Korean Information Science Society Conference
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    • 1998.10c
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    • pp.488-490
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    • 1998
  • 본 논문에서는 차량 영역 정보를 이용한 교통 혼잡도 측정 시스템을 설계하고 구현한다. 제시한 교통 혼잡도 측정 시스템은 첫째 영역 분할, 둘째 작은 영역의 직사각형화, 셋째 영역의 병합 및 삭제의 세 단계로 나눌 수 있다. 영역 분할 단계에서 획득한 도로 영상을 주어진 임계치에 의해 영역으로 분할한다. 영역 분할후의 영역 정보 중 차량 영역을 추출하는데 영향을 미치지 않는 작은 영역들을 제거하고 영역을 직사각형화하는 단계를 거친다. 이 단계에서 필요없는 많은 작은 영역 정보들을 제거한다. 마지막으로 차선 별로 영역을 병합, 삭제함으로써 각 차선마다 차량 영역 정보를 추출할 수 있다. 본 논문에서는 이러한 차량 영역 정보를 추출하는 방법을 제시하며, 또한 이를 이용한 효과적인 교통 혼잡도 측정 시스템을 소개하고 평가한다.

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TCP Congestion Control for Fast Bandwidth Acquisition for Networks with Large Bandwidth (대역폭이 큰 네트워크에서 빠른 대역폭을 확보하기 위한 TCP 혼잡 제어)

  • Kim, Seung-Hwan;Park, Min-Woo;Lim, Hun-Jung;Chung, Tai-Myoung
    • Proceedings of the Korea Information Processing Society Conference
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    • 2009.04a
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    • pp.1352-1355
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    • 2009
  • TCP에서 사용되는 혼잡제어(Congestion control)는 많은 이점이 있지만 그에 상응하는 단점이 존재한다. 가장 널리 사용되고 있는 TCP-Reno는 혼잡이 발생되면 혼잡 윈도우(Congestion Window)크기를 절반으로 줄이고 빠른 회복(fast recovery), 빠른 재전송(fast transmit)을 수행한다. 하지만 네트워크가 고속 네트워크로 접어들면서 효율적인 측면에서 이러한 기법들을 적용하기에는 문제가 따른다. 현재 사용되고 있는 TCP는 혼잡이 발생하면 선형적으로 점진적으로 증가 하기 때문에 많은 대역폭을 지원하는 고속 네트워크에서는 이러한 TCP의 혼잡 제어가 오히려 비 효율적이다. 본 논문에서는 이러한 문제점을 해결하기 위해 혼잡 윈도우 증가율을 추가한 혼잡제어 기법인 TCP-FBA(Fast Bandwidth Acquisition)를 제안한다.

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Study on Methodology for Effect Evaluation of Information Offering to Rail passengers - Focusing on the Gate Metering Case Study considering congested conditions at a platform - (철도 이용객 정보제공 효과평가 방법론 연구 - 승강장의 혼잡상황을 고려한 Gate Metering 사례 연구 중심으로 -)

  • Lee, Seon-Ha;Cheon, Choon-Keun;Jung, Byung-Doo;Yu, Byung-Young;Kim, Eun-Ji
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.14 no.3
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    • pp.50-62
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    • 2015
  • Recently, Subway Line No. 9, described as a 'hell-like' subway for its recorded load factor of max. 240% due to the opening of the 2nd phase extension section, has been causing problems of recurrent congestion in a subway station building. A recurrent congestion in the station building becomes a factor to offend rail users and to reduce the efficiency of railway management. This study aims to establish the methodology for effect evaluation of information provided to rail users, and conducts a gate metering case study considering the congested conditions at a platform among the methodologies for effect evaluation. The metering effect evaluation by load factor was conducted through selecting the micro simulation and pedestrian simulation tool grafting a gate metering. As a result, it was confirmed that, if gate metering is performed, the service level and pedestrian density of a platform by load factor would improve. In other words, if metering is conducted at a platform, it is possible to control the load factor in the waiting space of a platform. Therefore, it was judged through this study that it is possible to set up the index for effect evaluation of information provided to manage congestion of rail users, and establish the methodology for effect evaluation of information provided to rail users through a program.

The Effect of Feedback Path Congestion on the Multimedia Congestion Control Algorithm (멀티미디어 혼잡제어 알고리즘에서의 회신경로 혼잡에 대한 영향 분석)

  • Jung Gi Sung;Hong Min-cheol;Yoo Myungsik
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.7B
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    • pp.481-488
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    • 2005
  • As the demand on the multimedia application increases, the congestion control algorithm for the multimedia applications becomes an important research issue. The ultimate goal of congestion control is to adapt the trans-mission rate at the sender to the mont of network resource available on the forward path. In general, the congestion control algorithms use the round trip time(RTT) to estimate the network congestion on the forward path. however, since the RTT includes the delay on both forward and backward paths, it is possible for the algorithms using the RTT to make a wrong decision such as deciding the congestion on the forward path due to the congestion built on the backward path. In this paper, we enhance the performance of RRC-OTT(Receiver-based rate control with one-way Trip Time) algorithm, which uses the one-way trip time(OTT) to estimate the network congestion. By separating the estimation mechanism on the forward path from the backward path, the performance of RRC-OTT algorithm is hardly affected by the congestion built on the backward path.

The Congestion Estimation based TCP Congestion Control Scheme using the Weighted Average Value of the RTT (RTT의 가중평균값을 이용한 혼잡 예측 기반 TCP 혼잡 제어 기법)

  • Lim, Min-Ki;Kim, Dong-Hoi
    • Journal of Digital Contents Society
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    • v.16 no.3
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    • pp.381-388
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    • 2015
  • TCP, which performs congestion control in congestion condition, is able to help a reliable transmission. However, packet loss can be increased because congestion window is increased by the time the packet is dropped in the process of congestion avoidance. In this paper, to solve the above problem, we propose a new congestion estimation based TCP congestion control scheme using the weighted average value of the RTT. After measuring a SRTT, which means the weighted average value of RTTs, at this point of time when a buffer overflow is occurred by an overloaded packet, the proposed scheme estimates the time, when the same SRTT is made in packet transmission, as a congestion time and then decreases the congestion window. The simulation results show that the proposed schem has a good performance in terms of packet loss rate and throughput when the packet loss due to buffer overflow is larger than that due to wireless channel.

Performance Improvement of TCP Vegas Using Estimation of End-to-End Forward/Backward Delay Variation (종단간 순방향/역방향 전송지연 측정을 이용한 TCP Vegas의 성능 향상)

  • Shin Young-Suk;Kim Eun-Gi
    • The KIPS Transactions:PartC
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    • v.13C no.3 s.106
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    • pp.353-358
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    • 2006
  • Unlike TCP Reno, TCP Vegas recognizes network congestion through the measuring of RTT (Round Trip Time) and decides the main congestion control parameters, such as Windows size. But, congestion avoidance scheme of Vegas poorly reflects asymmetric characteristics of packet path because TCP Vegas uses the measuring of RTT that reflects forward/backward packet transmission delay as a forward delay. The RTT can't infer the forward/backward transmission delay variation because it only measures the packet's turn around time. In this paper, We have designed and implemented a new Vegas congestion control algorithm that can distinguish forward/backward network congestion. We have modified the source codes of TCP Vegas in Linux 2.6 kernel and verified their performance.

Study on the Development of Congestion Index for Expressway Service Areas Based on Floating Population Big Data (유동인구 빅데이터 기반 고속도로 휴게소 혼잡지표 개발 연구)

  • Kim, Hae;Lee, Hwan-Pil;Kwon, Cheolwoo;Park, Sungho;Park, Sangmin;Yun, Ilsoo
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.17 no.4
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    • pp.99-111
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    • 2018
  • Service areas in expressways are very important facilities in terms of efficient expressway operation and the convenience of users. It needs a traffic management strategy to inform drivers in advance about congestion in service areas so as to distribute users of service areas. But due to the lack of sensors and data on numbers of people in the service areas, congestion in service areas had not been measured and managed appropriately. In this study, a congestion index for service areas was developed using telecommunication floating population big data. Two alternative indices (i.e., density of service areas and floating population V/c of service areas) were developed. Finally, the floating population V/c of service areas was selected as a congestion index for service areas for reasons of the ease of understanding and comparison.

Congestion Control Using Active Network and Active Queue Management (액티브 네트워크 기술과 액티브 큐 매니지먼트를 이용한 혼잡제어)

  • Choi, Kee-Hyun;Jang, Kyung-Soo;Shin, Ho-Jin;Shin, Dong-Ryeol
    • Proceedings of the Korea Information Processing Society Conference
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    • 2002.04b
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    • pp.1345-1348
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    • 2002
  • 기존의 TCP/IP 네트워크 상에서 혼잡을 제어하는 일반적인 방법은 end-to-end 피드백 방식이다. 혼잡이 발생했는지의 여부는 수신측의 ACK 신호로 예측할 수밖에 없으므로 RTT(round trip time)가 길어질 경우 혼잡처리 시간이 길어지게 된다. Active Network 기술을 이용한 ACC(Active Congestion Control)의 경우 혼잡이 발생한 라우터에서 전송자에게 직접적으로 정보를 전송하기 때문에 보다 빠른 혼잡처리가 가능하다. 비록 코어 라우터에서 패킷을 누락시키는 방법에 있어 상태정보를 필요로 하는 단점이 있지만 모의 실험 결과 향상된 처리량을 보여주었다. 혼잡처리에 있어 새로운 처리 방식은 AQM(Active Queue Management)이다. 이 방식은 RED 를 기본 모델로 변형된 것이 대부분이며 RED 가 갖는 단점을 개선하고 혼잡처리와 공평성(fairness)을 향상 시키는데 목적이 있다. 본 논문에서는 ACC 의 피드백 메커니즘과 AQM 의 융통성 있는 큐 관리 기법을 이용하여 보다 향상된 혼잡제어 기법을 보이겠다.

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The Evaluation of Existing Congestion Indices' Applicability for Development of Traffic Condition Index (소통관리 지표 개발을 위한 기존 혼잡지표의 국내 적용성평가 연구)

  • Lee, Seung-Jun;Kim, Tae-Young;Ko, Han-Geom;Bok, Ki-Chan
    • International Journal of Highway Engineering
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    • v.10 no.3
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    • pp.119-128
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    • 2008
  • On the many highways, severe traffic congestions happen chronically and make traffic problems like reduction of mobility because of rapid increase of vehicles though road construction has been last. In order to solve these traffic problems, it is needed to find the trend and the symptom of traffic congestion and to analyze the cause of congestion and the(spatial) range affected by congestion. To develop the traffic condition monitoring index prior to doing all those things is most important. With this reason, many countries including U.S. had been developed the congestion criteria and indices. In this paper, applicability and characteristics of existing traffic congestion indices were considered and the direction for development of a new traffic condition index was suggested to achieve an effective traffic management.

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