Allied Telesis AT-S63 - Manual (Page 319)

AT-S63 Management Software Menus Interface User’s Guide
Section II: Advanced Operations 319
Note
CoS does not change the tagged information in a frame. A tagged
frame leaves a switch with the same priority level that it had when it
entered.
The default for this parameter is No, meaning that the priority level of
tagged frames is determined by the priority level specified in the
frames themselves.
8. Type C to select Configure Port COS Priorities.
A change to a port CoS setting is immediately activated on the port.
9. To permanently save your change, return to the Main Menu and type S
to select Save Configuration Changes.