Packet Capture Device Dual Timer Timestamp Correction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In packet capture devices, direct correction of the local timer value can lead to time stamp mismatches in pcap files, making it difficult to identify packets around failure occurrence times during failure analysis.

Innovation Solution

A packet capture device with two local timers, where the first timer is synchronized with a global timer and the second timer assigns time stamps, and a difference calculation unit corrects the time stamp values based on the timer value difference between the two timers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the local timer value is directly corrected based on the global timer value, then the timer synchronization with the global timer is improved, but the time stamp sequence continuity deteriorates causing future timestamps to appear before past timestamps

Engineering Contradiction:

Improvetimer synchronization accuracyVSAvoidtime stamp sequence continuity

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The patent divides the timer system into two separate local timers: a first local timer that synchronizes with the global timer to ensure accuracy, and a second local timer that continuously increments to maintain timestamp sequence continuity. This segmentation allows each timer to fulfill its specific function without interfering with the other's operational integrity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a difference calculation unit as an intermediary that calculates the time difference between the first and second local timers. This intermediary component enables the system to compensate for drift by adjusting timestamps based on the calculated difference, thereby maintaining both synchronization accuracy and sequence continuity without directly correcting the second timer's running value.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If the local timer is synchronized with the global timer using a single timer, then the synchronization is simplified, but the device complexity increases due to the need for timestamp correction mechanisms

Engineering Contradiction:

Improvetimer system structureVSAvoidtimestamp accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second local timer operates autonomously by continuously incrementing without requiring direct correction, maintaining sequence continuity on its own. The difference calculation unit periodically compensates for drift by calculating the time difference and adjusting timestamps, allowing the system to self-regulate while maintaining both accuracy and continuity.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS12126509B2Packet capture device, time stamp amendment method, packet capture method and packet capture program

Publication Date: 2024.10.22 NIPPON TELEGRAPH & TELEPHONE CORP

AI summary

An embodiment is a packet capture device including a first local timer synchronized with an external global timer, a second local timer, a time stamp assign unit for assigning a time stamp to a inputted packet signal based on the second local timer, a filter unit for selecting the packet signal to which the time stamp is assigned, a capture file generation unit for receiving the selected packet signal, and a storage unit for storing a capture file generated in the capture file generation unit, wherein the capture file generation unit calculate a difference between a timer value of the first local timer and a timer value of the second local timer to correct the time stamp value on the basis of the difference.