QoS troubleshooting with Wireshark

QoS

During my work i have a lot of VoIP traffic related queries/questions. I’m using this configuration to check if packets are being tagged with the right DSCP values.

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Add DSCP column to your Wireshark Client

1. Right click on one of the existing columns.
2. Click on column preferences
3. Click Add down the bottom
4. Click on the “New Column” Label and change it to “DSCP” then hit enter once.
5. With the new entry highlighted, change the Field Type to Custom (in the dropdown box)
6. In field name, copy and paste in _ip.dsfield.dscp
7. Click Apply/Ok

You can drag the column back to the left side of the Info column and you now have a simple view of the tag for any packet.

Filter

You can also set a filter to capture all packets with DSCP value 46

ip.dsfield.dscp == 46

Reference

Here’s a table of DSCP and TOS values in their most common formats just for reference.