Allied Telesis AT-S25 - Manual (Page 164)

Section II: Local and Telnet Mangement
164
You could also use CoS to control which priority queue handles
untagged frames that ingress a port. By default, untagged frames (i.e.,
frames without VLAN or priority level information) are automatically
assigned to the low priority buffer. But you could configure CoS on a
port so that all untagged frames received on the port are directed to the
high priority queue.