This page is part of the GENIUS project.
Calibration Tests for Intel CA810e based computer
This test was used to determine the accuracy of the Intel CA810e with bursts of fixed-spaced ethernet packets. In particular, to look at the effects of an additional network card to the configuration with respect to the timestamping of packets.
Figure 7.
Setup of Hardware for Intel CA810e Packet Sniffing Computer Calibration
Tests cases conducted were:
| Interval | Duration |
|---|---|
| 125usec (124.8usec) | 5min |
| 300usec | 2min |
| 1000usec | 2min |
| 5000usec | 2min |
Results
The tables below detail the Mean, Variance and Standard Deviation values for the test cases generated. All values are in microseconds.
| Interval | Without Interface vr0 | With Interface vr0 | ||||
|---|---|---|---|---|---|---|
| Mean | Var | Std Dev | Mean | Var | Std Dev | |
| 125usec | 208.0 | 7.0 | 2.6 | 208.0 | 1362.9 | 36.9 |
| 300usec | 383.2 | 7.6 | 2.8 | 383.2 | 2431.4 | 49.3 |
| 1000usec | 1083.1 | 4.7 | 2.2 | 1083.1 | 6643.6 | 81.5 |
| 5000usec | 5083.0 | 4.0 | 2.0 | 5083.0 | 11042.0 | 105.1 |
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| 125usec Interval, without vr0 Figure 8. |
125usec Interval, with vr0 Figure 9. |
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| 300usec Interval, without vr0 Figure 10. |
300usec Interval, with vr0 Figure 11. |
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| 1000usec Interval, without vr0 Figure 12. |
1000usec Interval, with vr0 Figure 13. |
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| 5000usec Interval, without vr0 Figure 14. |
5000usec Interval, with vr0 Figure 15. |
Note: Although the above tests were run for 5 minutes duration, only a snap shot of this data is shown above due to limitations with Microsoft Excel. The entire data that was collected has been checked and is consistent with the above representative samples.
From the results above it can observed that an interesting time stamping error with interface vr0 present (2nd network card installed). This error occurs every second, whereby a packet is incorrectly time stamped up to 2.5 milliseconds greater than the mean interpacket arrival time. This behaviour was only seen on the CA810e-based system (600MHz Celeron CA810e Intel motherboard running FreeBSD 4.6).
Also note, that for the graphs above with vr0 present the duration between each of the outlying time stamped packets was approximately 1 second. Hence, the number of packets between these outliers is dependent upon the fixed-space interval for each test case (ie. The smaller fixed-interval the greater the number of packets between outliers and vice-versa).
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