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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 (Dept. of Electrical and Electronic Engineering, College of Information Technology, Kangwon National University) ;
  • Kim, Dong-Hoi (Dept. of Electrical and Electronic Engineering, College of Information Technology, Kangwon National University)
  • Received : 2015.04.01
  • Accepted : 2015.05.30
  • Published : 2015.06.30

Abstract

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.

TCP(Transmission Control Protocol)는 혼잡한 상황에서 혼잡 제어를 수행하므로 신뢰성 있는 전송을 할 수 있지만 혼잡 회피(Congestion avoidance) 과정에서 혼잡으로 인한 패킷 드롭이 일어날 때까지 혼잡 윈도우의 크기를 증가시키므로 패킷 손실이 증가할 수도 있다. 본 논문에서는 상기 문제점을 해결하기 위하여 RTT(Round Trip Time)를 이용한 새로운 혼잡 예측 TCP 혼잡 제어 기법을 제안한다. 제안하는 기법은 과도한 패킷 누적으로 인한 버퍼 오버플로우가 발생하는 시점에서 RTT 값들의 가중평균값인 SRTT(Smooth RTT)값을 측정한 후 패킷 전송 시에 같은 SRTT값을 가질 때를 혼잡한 상황이라 예측하여 혼잡 윈도우를 감소시키는 알고리즘이다. 시뮬레이션 결과를 통하여, 제안하는 기법이 무선 구간에 의한 패킷 손실보다는 버퍼 오버플로우에 의한 패킷 손실이 클 경우에 패킷 손실률과 처리량 측면에서 좋은 성능을 가지는 것을 확인할 수 있었다.

Keywords

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