Retransmission Server Bandwidth Control for TCP
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Solution Overview
Problem
In communication using TCP, the transmission bandwidth is significantly influenced by RTT and discard rate, leading to bandwidths lower than contracted levels in environments with large RTT and many discarded segments.
Innovation Solution
A communication apparatus and system that includes means for notifying and retransmitting discarded segments, and controlling transmission bandwidth based on retransmission and discard bandwidth, thereby reducing the influence of RTT and discard rate on transmission bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If TCP communication is used with RTT and discard detection for bandwidth control, then network congestion is avoided, but transmission bandwidth is significantly reduced in environments with large RTT and high discard rates
Solution Approach 1:
A retransmission server is introduced as an intermediary between the transmitting terminal and receiving terminal. The retransmission server receives discarded segments from the transmitting terminal, stores them, and retransmits them to the receiving terminal. This mediator approach allows the original TCP communication to maintain its congestion avoidance mechanisms while the retransmission server compensates for bandwidth loss by handling retransmissions separately, thus resolving the contradiction between reliability and productivity.
2Reliability
If window size is decreased in response to RTT increase or discard detection, then network congestion is avoided, but transmission bandwidth is indirectly decreased
Solution Approach 1:
The transmission process is segmented into two independent paths: the original TCP path that maintains congestion avoidance through window size adjustment, and a separate retransmission path that handles discarded segments. By dividing the transmission function, the system preserves the reliability mechanism of window control while the retransmission path compensates for bandwidth reduction, effectively resolving the contradiction between congestion avoidance and bandwidth maintenance.
Data Source
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AI summary
In communication using TCP, since the transmission bandwidth is significantly influenced by RTT and discard rate, there was a problem that only the transmission bandwidth significantly lower than the contracted bandwidth could be obtained under the environment such as WAN causing large RTT, large hop number and many discarded segments. There is provided an apparatus connected to a receiving side terminal having a means for feeding back to notify all discarded segments to an apparatus connected to a transmitting side terminal; a means for retransmitting the discarded segments fed back to be notified to the apparatus connected to the transmitting side terminal; and a means for controlling transmission bandwidth, based on retransmission bandwidth and discard bandwidth by the apparatus connected to the transmitting side terminal.