Allied Telesis AT-S39 - Manual (Page 290)

Section III: Web Browser Management
290
Path Cost
Though it says path cost, this is actually the port cost of the port.
The spanning tree algorithm uses port cost to decide which port
provides the lowest cost path to the root bridge for that LAN. The
default values for this parameter are 100 for a 10 Mbps port, 10 for
a 100 Mbps port, and 4 for a 1 Gbps port. The range is 1 to 65535.
Port Priority
This parameter is used as a tie breaker when two or more ports are
determined to have equal costs to the root bridge. The default
value for priority is 128. The range is 0-255.
Fast Mode
When you check this check box, the port will skip the Listening
and Learning stages of STP. This setting is appropriate for ports
connected to edge nodes that are not running STP.
Port State
This field indicates the STP state of the port, which can be
listening, learning, forwarding, or blocked. This value is for display
purposes only and cannot be changed.
Root Bridge
The MAC address of the bridge functioning as the root bridge in
the spanning tree domain. This value is for display purposes only
and cannot be changed. If STP has not been enabled, this
parameter will not show a value.
4. Once you have configured the parameters, click Apply.
All changes are immediately activated on the switch.