What are the three models of quality of service （QoS） in a network？（）

多项选择题WhichtwostatementsaretrueaboutVoiceoverIP（VoIP）packetdeliveryinadigitalinfrastructure？（）

A. Packets can arrive out of order.
B. Packets must take the same path to the destination.
C. Once packets are received at the destination router， the router performs sampling to ensure the quality of the voice traffic.
D. Packets can experience varying delays across the network.
E. Packets containing voice samples are sequentially numbered by default， allowing for reordering upon arrival at the terminal router along the path.

多项选择题Fordelaysensitivetraffic，whatarethethreebestwaysthatareusedtopreventpacketloss？（）

A. Compress payload.
B. Use header compression.
C. Increase link capacity.
D. Use random early detection.
E. Guarantee bandwidth to fragile flows.
F. Implement network-based application recognition.

多项选择题WhichthreefunctionsareassociatedwithaCiscoUnifiedCallManager？（）

A. connects traditional telephony devices to voice over IP infrastructure
B. converts analog signals to digital format
C. performs voice compression
D. performs call processing
E. performs dial plan administration
F. performs signaling and device control

多项选择题Whichtwocharacteristicsarecommonbetweentrafficpolicingandtrafficshaping？（）

A. The rate of traffic is measured and compared to a configured policy.
B. Classification is used to differentiate traffic.
C. Traffic is marked and sent out according to priority.
D. Both can be applied to inbound and outbound traffic.
E. Both buffer traffic to ensure a predetermined traffic rate.
F. Both drop traffic that is above a predetermined traffic rate.

多项选择题WhichtwoQoSclassificationandmarkingstatementsaretrue？（）

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 802.1Q standard uses a three bit field referred to as the user priority bits （PRI） to mark packets as belonging to a specific CoS.