A. If the classification policy is based upon the ToS byte， the qos pre-classify command is required because the ToS byte only appears in the inner IP header.
B. The ToS byte is copied to the outer header by default. Therefore， the qos pre-classify command is not necessary.
C. With GRE encapsulation， the qos pre-classify command is applied on the tunnel interface. This practice allows for different OoS configurations on each tunnel.
D. With GRE encapsulation， the qos pre-classify command is applied on the physical interface. This practice allows for different OoS configurations on each interface.
E. With IPsec encapsulation， the qos pre-classify command is applied on the physical interface. This practice allows for different OoS configurations on each interface.

A. In a Frame Relay network， delay sensitive traffic is tagged with the discard eligible （DE） bit.
B. In an MPLS network， the three most significant bits of the DSCP or the IP precedence of the IP packet are copied into the MPLS EXP field
C. In an MPLS network， the MPLS EXP bits are used to identify up to 16 CoS values.
D. The differentiated services code point （DSCP） field consists of the first three bits of the IP precedence field in the header of an IP packet.
E. The 802.10 standard uses a three bitfield referred to as the user priority bits （PRI） to mark packets as belonging to a specific CoS.