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

多项选择题WhataretworeasonstoimplementH·323gatekeepers？（）

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

多项选择题WhatarethreefactorsusedtodeterminetheamountofbandwidththatisrequiredforasingleVoIPcall？（）

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

多项选择题WhataretwowaystominimizethedelayofVoIPpacketsthataretraversinganetwork？（）

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.

多项选择题WhatarethreeCiscoUnifiedCallManagerfeatures？（）

A. programming interface to external applications
B. FXS and FXO port negotiation
C. AutoQos VoIP trust boundaries
D. signaling and device control
E. LLQ for voice and video traffic
F. directory and XML services

多项选择题WhataretwocomponentsoftheQoSIntegratedServices（IntServ）model？（）

A. link efficiency
B. admission control
C. classification and marking
D. shaping and policing
E. congestion avoidance using the RTP protocol
F. resource reservation using the RSVP protocol