Segmented RTT Measurement for Packet Flow Control
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Solution Overview
Problem
The existing flow control method using the SICC scheme and TFRC for packet delivery to multiple terminals with varying speeds results in unnecessarily low data transmission rates due to increased RTT measurements during concatenated transfers, leading to performance deterioration.
Innovation Solution
The method involves calculating and selecting the round trip time (RTT) for each pair of adjoining terminals on the delivery route, using divided RTT measurement to estimate a higher transmission rate, thereby avoiding the calculation of large RTT values and improving packet transmission performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If concatenated transfer is performed through multiple receiving terminals, then data can be delivered to multiple terminals with varying capacities, but the round trip time (RTT) increases causing unnecessarily low transmission rates
Solution Approach 1:
The patent segments the RTT measurement into multiple parts, measuring RTT between each pair of adjoining terminals (transmitting terminal to first receiving terminal, first receiving terminal to second receiving terminal, etc.) rather than measuring the entire concatenated path RTT. This segmentation prevents the RTT from increasing proportionally with the number of relay terminals, thereby maintaining higher transmission rates while still enabling delivery to multiple terminals with varying capacities.
2Reliability
If flow control is performed based on end-to-end RTT measurement, then TCP affinity is maintained, but transmission performance deteriorates due to large RTT values in concatenated transfer
Solution Approach 1:
The patent segments the RTT measurement path into multiple measurement segments between adjoining terminals. Each segment's RTT is measured separately and the maximum of these segmented RTTs is used for flow control calculations. This approach maintains TCP affinity by still performing flow control based on RTT measurements, while avoiding the performance deterioration caused by using the large end-to-end RTT of the entire concatenated path.
Solution Approach 2:
The patent changes the parameter used for flow control from the end-to-end RTT of the concatenated path to the maximum RTT among segmented measurements between adjoining terminals. This parameter change ensures that the flow control mechanism continues to operate based on RTT (maintaining TCP affinity) while using a smaller, more accurate RTT value that reflects the actual bottleneck in the path, thereby improving transmission performance.
3Reliability
If the transmission rate is limited by the slowest terminal (ADSL), then all terminals can receive data, but high-capacity terminals (optical fiber) cannot utilize their full receiving capacity
Solution Approach 1:
The patent segments the delivery path into multiple hops between adjoining terminals and measures RTT for each segment. By using the maximum RTT among these segments for flow control, the system can identify the actual bottleneck in the path. This allows the transmission rate to be adjusted based on the real bottleneck rather than assuming the slowest terminal limits the entire path, enabling high-capacity terminals to utilize their full receiving capacity when they are not the bottleneck.
Solution Approach 2:
The patent changes the flow control parameter from using the RTT of the slowest terminal to using the maximum RTT among segmented measurements. This parameter change enables more accurate identification of the actual bottleneck in the concatenated path, allowing the transmission rate to be optimized for each specific path configuration. As a result, high-capacity terminals can achieve their full receiving capacity when the bottleneck lies elsewhere in the path, while still maintaining fairness when they are indeed the limiting factor.
Data Source
AI summary
It is an object to provide a flow control method in which a packet round trip time is not excessively calculated out and its performance is not unnecessarily deteriorated even at the time of continuously connected packet transfers through relays of a plurality of receiving terminal devices. This method is directed to a flow control method in which the delivery of packets are carried out through relays of a plurality of receiving terminal devices. The method is comprised of steps (S501-S517) for acquiring a packet round trip time for every pair of neighboring terminal devices in a path of the delivery, a selection step for selecting one from the acquired round trip time in accordance with a predetermined standard, and a step (S518) for calculating a packet transmission rate on the basis of the selected round trip time, so that the round trip time of each receiving terminal device is measured and the transmission rate is calculated in accordance with the measured result. Thus, a packet round trip time is not excessively calculated out, and data transmission performance can be improved.