Packet Jitter Calculation Without Prescribed Clock Frequency
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Solution Overview
Problem
In communication systems using protocols like RTP, where the clock frequency is not prescribed in advance, especially in encrypted communications, it is difficult to calculate jitters such as instantaneous and average jitter without knowing the clock frequency.
Innovation Solution
A packet monitoring apparatus is coupled to a communication line, which captures packets, calculates capturing time intervals, determines clock frequencies, and estimates jitter by analyzing timestamp differences and acquisition time intervals, enabling jitter calculation even when the clock frequency is unknown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the clock frequency is not prescribed in advance (encrypted communications), then communication security is improved, but the ability to calculate jitter is worsened
Solution Approach 1:
The patent introduces an intermediary calculation method that uses capturing time intervals and clock numbers as mediators to indirectly determine jitter without requiring direct access to clock frequency information. By measuring the time intervals between captured packets and comparing clock numbers from timestamps, the system can calculate jitter as a ratio, serving as an intermediary approach that bypasses the need for prescribed clock frequency while maintaining measurement capability
Solution Approach 2:
The patent changes the measurement parameters from direct clock frequency measurement to alternative parameters (capturing time intervals and clock number differences). By transforming the measurement approach to use these alternative parameters and calculating jitter as a ratio between them, the system adapts to conditions where clock frequency is not prescribed, converting the measurement problem into a solvable form using different parameters
2Ease of operation
If clock frequency is prescribed in advance, then jitter calculation is simplified, but adaptability to encrypted communications is worsened
Solution Approach 1:
The patent creates a universal jitter measurement method that functions in both prescribed and non-prescribed clock frequency scenarios. By formulating jitter as a ratio of capturing time interval to clock number difference, the measurement approach becomes multi-functional, working whether or not clock frequency is prescribed in advance, thus achieving versatility across different communication types including encrypted communications
Data Source
AI summary
A packet monitoring apparatus includes a memory and a processor configured to capture a plurality of packets transmitted through a communication line and belonging to a first session, specify capturing time intervals between the plurality of packets, acquire, from each of the plurality of packets, a clock number of clocks generated by a transmission apparatus and counted when each of the plurality of packets is transmitted from the transmission apparatus, specify a difference of the clock numbers between each of the plurality of packets and a packet captured immediately prior to each of the plurality of packets, specify a frequency of the clock based on the specified capturing time interval and the specified difference, and specify a jitter of the capturing time intervals based on the specified capturing time interval, the specified frequency, and the specified difference.