Answer:
for VoIP falls in Digital IP end to end categories
Step-by-step explanation:
Normally to address the VoIP solution the phone or PABX should be the only digital module. All the telephone extensions are connected to switch and from the switch, it should be connected to the digital module in PABX. If existing PABX is analog then end-user has to purchase digital module
conversion to attach to analog PABX
Then switch which should be managed switch for better performance. Suppose it we use the switch as an unmanaged switch then the performance of VoIP will be very less effective. Since VoIP is used for internet purpose also better to use end to end digital mode.