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Spirent KB Article
Doc ID: SOL13944
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Spirent TestCenter: Comparing Tx and Rx to verify DUT changed a value.
Objective/Summary
DSCP Verify
Diffserve Verify
CoS Verify
ToS Verify
Environment/Versions
The information provided is for the full Diffserv/ToS byte value.
Procedure
Configure an analyzer custom filter:
Go to Traffic Analyzer on the STC RX Port, and select Custom Filters Tab.
Click on +Add, 16 Bit Filter, you only need to modify:
Offset
Mask
The rest of the settings will remain as default
Index = 0
Location Type = Start Of Frame
Start Of Range = 0
End of Range = FFFF
To find out the
Offset
:
Using a capture on the STC RX Port find out the frame location ofsset where the DiffServ/DSCP value is found.
On a default streamblock (no more headers added), the DiffServ is found in byte 15, as you can see in the capture:
The Offset will be = (The number of bytes from the beginning of the filter where the filtered data (DiffServ/DSCP) is found)
- 1
The reason we substract 1 to the real offset is because at the end the filtered value will still be a 16-bit value, but we need to preserve ONLY the last 8 bit (to get an acurate value) from the value and rid-off the first 8 bits of the same (ignoring them and make them all 0's), on that way we'll get a 16-bit value like this: 0000 0000 XXXX XXXX, where X will be the DSCP value
To find out the
Mask:
Same explanation as above, since we need to preserve the last 8 bits from the 16-bit value and rid-off the first 8 bits of the same (ignoring them and make them all 0's), the mask will be
00FF
(GUI will show only FF, that is OK)
Create a DRV
Expand the StreamBlock Counter in the columns tab.
Select the columns you want and also add
16-bit analyzer filter #1, 16-bit analyzer filter #2, 16-bit analyzer filter #3 and 16-bit analyzer filter #4
, which is under the StreamBlock Basic Counters.
The reason you need to select all filters # is because depending on how much filters there is, the display might be on filter #4, #3, #2 or #1, so the best is to display all filters so you can see which one contains it.
Select the Config tab and add the
IPv4 Header.ToS/Diffserv
Create a Custom Property by clicking on the green plus sign
Select the
16-bit analyzer filter #X
which is under the StreamBlock Basic Counters
Select ==
Select the Config tab and add the
IPv4 Header.ToS/Diffserv
Select expression type boolean
Stream was configured to send diffserv byte value of D2 which is 210 decimal.
The comparison now shows Tx and Rx is 210 so the Verify is True
Attachments
Attachment
SOL13944_STC-example.tcc
Version
4.0
Publish Date
2023-03-13
Categories
Product : Spirent TestCenter,PGA
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