Time-Varying Latency Estimation via Network Trace Analysis
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Solution Overview
Problem
Existing network analysis tools face challenges in accurately estimating time-varying network latency using limited traffic trace information, particularly due to insufficient monitoring device coverage and varying network conditions.
Innovation Solution
A method and system that estimate time-varying latency based on round-trip time, refining estimates by weighting immediate and delayed responses, applying TCP-specific constraints, and accounting for physical limitations to avoid unrealistic results, using equations to calculate latency from reliable round-trip time measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If network monitoring devices are placed at each node location to accurately record message transmission and reception times, then measurement precision of latency is improved, but device complexity and cost increase substantially
Solution Approach 1:
The patent uses trace information from limited monitoring devices as an intermediary to infer latency characteristics across the entire network. Instead of placing monitors at every node, the system captures traffic traces at strategic points and uses these traces to estimate latency for packets that passed through unmonitored nodes, effectively using available trace data as a mediator to bridge the gap between limited monitoring coverage and comprehensive latency measurement.
Solution Approach 2:
The system creates virtual copies of monitoring capabilities by using trace information to reconstruct latency measurements for unmonitored network paths. The trace data serves as a copy or representation of actual packet transmission behavior, allowing the system to estimate latency for packets that weren't directly observed by monitoring devices, thereby extending measurement capability beyond physical monitor locations.
2Productivity
If round-trip time measurements are used to estimate latency, then productivity of network analysis is improved, but measurement precision deteriorates due to unknown delays including processing delays and bandwidth-dependent delays
Solution Approach 1:
The patent segments the total round-trip time into distinct components: bandwidth-dependent delay (calculable from packet size and link bandwidth), processing delay (at source and destination nodes), and true network latency (the unknown component). By separating these elements, the system can estimate latency by subtracting the calculable bandwidth-dependent portion from the measured round-trip time, thereby improving precision despite the presence of other unknown delays.
Solution Approach 2:
The system changes the parameter being measured from raw round-trip time to derived latency by applying transformations: latency = round-trip time - bandwidth-dependent delay - processing delay. This parameter transformation allows the system to extract the meaningful latency component from the composite round-trip time measurement, improving precision by removing known confounding factors.
3Measurement precision
If latency estimates are refined by applying physical constraints and TCP-specific assumptions, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary filtering and constraint checking to latency estimates before they are used for network analysis. Physical constraints (such as ensuring latency is non-negative and consistent with known network topology) and TCP-specific assumptions (such as accounting for TCP processing behavior at endpoints) are applied in advance to refine raw latency measurements, improving precision by eliminating physically impossible or inconsistent estimates before they propagate through the analysis system.
Data Source
AI summary
Time-varying latency is estimated based on the round-trip time between the time of sending a message and the time of receiving an acknowledgement of receipt of the message. The round-trip time relative to a transmitter is modeled as a combination of known, or determinable, delays, plus an unknown latency, plus a processing/acknowledgement delay at the receiver. The estimated time-varying latency is further refined to give more weight to estimates based on fewer unknowns or a lesser magnitude of unknowns, and to impose physical constraints, such as assuring that the estimate does not imply an unrealizable event. TCP-specific constraints and assumptions are also applied to further refine the latency estimates.