Round-Trip Delay Measurement Using Fixed-Size Packet Buffers
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Solution Overview
Problem
Existing methods for measuring round-trip delay time in networks are inaccurate due to inclusion of generation delays on the inbound path and differences in packet sizes between measurement and return packets, which affect the calculation accuracy.
Innovation Solution
A system where a measurement packet is transmitted with a specified processing time included in the return packet, ensuring both packets have the same size, allowing for accurate subtraction of processing time from the total delay to determine the round-trip delay time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a return packet is generated by appending reception time point and transmission time point information to the measurement packet, then the round-trip delay time can be calculated, but the packet sizes of measurement packet and return packet differ, reducing measurement accuracy
Solution Approach 1:
The patent changes the parameter of packet size by using fixed-size buffer areas in the measurement packet to store timing information. Instead of appending variable-length information to the return packet, the system pre-allocates fixed-size fields in the original measurement packet, ensuring both packets maintain identical sizes while still capturing the necessary reception and transmission time points for accurate delay calculation.
2Ease of manufacture
If the generation timing of the inbound path packet train is not specified, then the system is simpler to implement, but the delay from reception to transmission is included in the round-trip delay time calculation, reducing accuracy
Solution Approach 1:
The patent applies preliminary action by pre-specifying the generation timing of the inbound path packet train. The transmission time point is determined in advance based on the reception time point of the outbound path packet train, ensuring that the processing delay is explicitly accounted for and separated from the actual network round-trip delay, thereby improving measurement accuracy without significantly complicating the system.
3Adaptability or versatility
If different packet sizes are used for measurement and return packets, then processing flexibility is improved, but the round-trip delay time calculation becomes inaccurate
Solution Approach 1:
The patent enforces homogeneity by making the measurement packet and return packet identical in size. This is achieved by using fixed-size buffer areas within the packet structure to store timing information, ensuring that both packets have the same dimensions. This homogeneous approach eliminates measurement errors caused by packet size differences while maintaining sufficient flexibility to capture necessary timing data.
Data Source
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AI summary
A communication device performs communication with an external device. The communication device includes: a measurement packet transmission unit that transmits a measurement packet at a first transmission time point; a return packet reception unit that receives a return packet at a second reception time point, the return packet being transmitted as a reply to the measurement packet at a second transmission time point by the external device, the return packet including information relating to a processing time indicating a duration from a first reception time point at which the measurement packet is received by the external device, to the second transmission time point, the return packet having a same packet size as the measurement packet; and a delay time specification unit that specifies, as a round-trip delay time, a duration obtained by subtracting the processing time from a duration from the first transmission time point to the second reception time point.