单项选择题 Which Cisco product family can simultaneously implement firewall, VPN, content security, network access control, virtualization, anD content filtering?（）

单项选择题 Which Internet Protocol(IP) telephony element is best categorizedas a voice application component?（）

单项选择题 Which IP telephony component provides call processing, such as signaling, that in a traditional voice network is provided by switching equipment, such as a PBX?（）