Refer to the exhibit. The network has been configured with H.323 gateways and gatekeepers as shown. Which statement is true when a call is placed？（）

 

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

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