Observa Telecom TD851W User Manual page 59

Phy port: The incoming port of the rule. It indicates the physical port of the traffic is incoming.
Set Priority: The priority of the rule. It can be p0(highest), p1, p2, p3(lowest). The traffic
matches the rule will be assigned the priority you have configured.
Insert or modify QoS mark: You can insert or modify the DSCP or 802.1p tag. The traffic
matches the rule will be added or modified the mark.
Note:
If you select 802.1p tag, please make sure 802.1q is enabled in specified WAN interface;
otherwise 802.1p tag will not be tagged.
Apply: After filling the parameters, click this button to add a new rule.
QoS Rule List: Shows the current rules on the device.
Delete: Select a rule then press the delete button, the selected rule will be deleted from QoS
rule list.
Delete all: Delete all the rules from QoS rule list.
4.3.3.2 802.1p
If the QoS policy is "802.1p based", you should configure the 802.1p setting.
TD851W 150Mbps Wireless N ADSL2+ Modem Router User Guide
53