A.WRED can selectively discard lower priority traffic when the interface becomes congested and can provide differentiated performance characteristics for different classes of service.
B.Resource Reservation Protocol （RSVP） and WRED cannot be configured on the same interface.
C.WRED will throttle back voice traffic only as a last resort.
D.If the average queue length is greater than the minimum threshold but less than the maximum threshold， then based on the drop probability， WRED will either queue the packet or perform a random drop.
E.WRED statistically drops more packets from low-bandwidth users than high-bandwidth users. Therefore， traffic sources that generate the least traffic are more likely to be slowed down than traffic sources that generate the most traffic.
F. WRED treats non-IP traffic as precedence 4.

A.SDMVoice
B.SDMSignal
C.SDMTrans
D.SDMManage
E.SDMRout
F.SDMBulk

A.Traffic bursts are smoothed out by queuing the excess traffic to produce a steadier flow of data
B.Excess traffic is buffered so that the traffic remains within the desired rate.
C.Packets that conform to traffic policies are not delayed.
D.Packet marking is available and allows excess packets to be re-marked with a lower priorit

A.Queuing introduces equal delays for packets of the same flow， resulting in jitter.
B.When congestion occurs， dropping affects most of the TCP sessions， which simultaneously back off and then restart again.
C.All buffers can temporarily be seized by aggressive flows， and normal TCP flows experience buffer starvation.
D.There is no differentiated drop mechanism. Higher priority traffic is dropped in the same way as best-effort traffic.
E.In TCP starvation， traffic exceeds the queue limit because of the bursty nature of packet networks. A router cannot handle multiple concurrent TCP sessions.
F.Global synchronization occurs because multiple TCP hosts reduce their transmission rates at random intervals in response to packet dropping

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.