What is the term that is used to describe the process of converting a signal from digital to analog？（）

A. to eliminate the need for VoIP gateways
B. to scale a VoIP installation with multiple gateways
C. to provide call admission control and limit the number of simultaneous calls on the network 
D. to meet the requirement to control H·323 gateways on a LAN
E. to accept call requests and reduce the load on the gateway

A. codec
B. link speed
C. Layer 2 encapsulation
D. packet overhead （IP/UDP/RTP）
E. link delay
F. total number of simultaneous calls that are allowed

A. Use WFQ， CBWFQ， and LLQ to prioritize delay-sensitive packets.
B. Use WFQ， CBWFQ， and LLQ to compress the payload.
C. Give TCP packets priority over UDP packets.
D. Use control plane policing for cRTP queuing.
E. Use stacker and predictor to compress the payload.