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?()
A、A.Client-based software, such as CiscoSoftPhone
B、B.Voice gateways, such as the Cisco VG248 Analog Phone Gateway
C、C.Call-management hardware and software, such as CiscoCallManager
D、D.Advanced call-handling software, such as Cisco Unity