I-TCP를 위한 이동성 지원 라우터에서의 버퍼 오버플로우 방지

Prevention of Buffer Overflow in the Mobility Support Router for I-TCP

  • 발행 : 2004.02.01

초록

I-TCP의 이동성 지원 라우터(MSR)의 버퍼가 넘치는 현상을 방지하기 위한 혼잡제어 알고리즘을 제안한다. 무선망 환경에서의 높은 비트 오류율와 잦은 핸드오프로 인해 유ㆍ무선이 혼재된 네트워크에서의 TCP Reno의 혼잡제어 방식은 유선으로만 이루어진 네트워크에서 보다 낮은 전송률을 보인다. 이를 해결하기 위해 하나의 TCP 연결을 유선과 무선부분 각각 두개의 TCP 연결로 나누어 처리하는 I-TCP가 제안되었다. 그러나 무선망의 비트 오류가 과다하게 발생하거나 핸드오프가 빈번하면 이동성 지원 라우터의 버퍼가 넘치는 현상이 발생할 수 있다. 이것은 MSR이 송신자에게 해달 ack를 보낸 패킷(MSR 버퍼에 있는)들이 수신자에게 전송되지 못하는 결과를 초래하여 TCP의 end-to-end semantic를 위반하게 된다. 본 논문에서는 송신자와 MSR 사이에 “흐름 제어” 기법을 도입하여 이동성 지원 라우터의 버퍼가 넘치는 현상을 방지하였다. 송신자와 MSR 사이의 advertised window를 MSR 버퍼의 남은 공간과 연동하여 MSR의 버퍼가 넘치기 전에 MSR로 전송되는 패킷의 양을 조절할 수 있다.

A congestion control algorithm to prevent buffer overflow in MSR(Mobility Support Router) for I-TCP is proposed. Due to high bit error rate and frequent hand-offs over wireless environment, the current congestion control scheme in TCP Reno over mixed(wired and wireless) network exhibits lower throughput than the throughput achieved over wired only network. I-TCP has been proposed to address this by splitting a TCP connection into two TCP connections over wired section and wireless section, respectively. However, buffer overflow in MSR may occur whenever there are excessive bit errors or frequent hand-offs. This may lead to the loss of packets acked by MSR(resident in buffer) to the sender, but not received by the receiver, breaking TCP end-to-end semantics. In this Paper, a new scheme is proposed to prevent the MSR buffer from overflow by introducing “flow control” between the sender and the MSR. Advertised window for the TCP connection between the sender and the MSR is tied to the remaining MSR buffer space, controlling the flow of packets to the MSR buffer before overflow occurs.

키워드

참고문헌

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