What is true about Quality of Service （QoS） for VPNs？（）

• 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