Allied Telesis AT-S106 - Manual (Page 62)

Chapter 4: Quality of Service (QoS)
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because untagged packets do not contain a priority level information. By
default, all untagged packets are placed in a port’s Q0 egress queue, the
queue with the lowest priority. But you can override this and instruct a
port’s untagged frames to be stored in a higher priority queue. The
procedure for this is also explained in “Configuring CoS” on page 65.
One last thing to note is that the CoS feature does not change the priority
level in a tagged packet. The packet leaves the switch with the same
priority it had when it entered. This is true even if you change the default
priority-to-egress queue mappings.
The default setting for the Quality of Service feature is disabled. When the
feature is disabled, all tagged packets are stored in the lowest priority
queue of a port.