问题：

[多选]

Refer to the exhibit. Which three statements are true about trust boundaries in the campus network？  （Choose three.）（）

A .  A device is trusted if it correctly classifies packets.
B .  A device is trusted if it correctly declassifies packets.
C .  The outermost trusted devices represent the trust boundary.
D .  Classification and marking occur using 802.1ab QoS bits before reaching the trust boundary.  
E .  Network trust boundaries are automatically configured in IOS version 12.3 and later.
F .  For scalability， classification should be done as close to the edge as possible.