单项选择题
A company implements video conferencing over IP on their Ethernet LAN. The users notice that the network slows down, and the video either stutters or fails completely. What is the most likely reason for this?（）
A.minimum cell rate (MCR) B.quality of service (QoS) C.modulation D.packet switching exchange (PSE) E.reliable transport protocol (RTP)
单项选择题 指定逻辑通道备份主接口使用的命令是（）。
多项选择题 Which two statements best describe the wireless security standard that is defined by WPA (Choose two.)（）。
单项选择题 What must be set correctly when configuring a serial interface so that higher-level protocols calculate the best route?（）
