A.QoS preclassification is only supported on generic routing encapsulation （GRE） and IPsec VPNs
B.QoS preclassification is not required in Layer 2 Tunneling Protocol （L2TP）， Layer2 Forwarding （L2F）， and Point-to-Point Tunneling Protocol （PPTP） VPNs
C.QoS preclassification is supported on IPsec AH VPNs， but not on IPsec ESP VPNs
D.the QoS-for-VPNs feature （QoS preclassification） is designed for VPN transport interfaces
E.with IPsec tunnel mode， the type of service （ToS） byte value is copied automatically from the original IP header to the tunnel header