Sazrika Foundation / Learn / VoIP vs PSTN
Interactive diagram

VoIP vs PSTN

Two completely different ways to make a phone call. One reserves a dedicated circuit. The other breaks your voice into packets and shares the internet with everyone else.

Traditional
PSTN Call
Circuit-switched — dedicated physical path
Modern
VoIP Call
Packet-switched — shared internet path
Network type
PSTN: Circuit-switched
VoIP: Packet-switched
Path
PSTN: Dedicated copper/fibre circuit
VoIP: Shared internet, any path
Bandwidth
PSTN: 64 Kbps reserved always
VoIP: 8–80 Kbps depending on codec
Quality
PSTN: Consistent, predictable
VoIP: Varies with internet quality
Cost
PSTN: Higher, distance-based
VoIP: Much cheaper, flat rate
Setup time
PSTN: ~1 second to establish circuit
VoIP: Near instant (SIP handshake)
Vulnerabilities
PSTN: Physical tap, SS7 attacks
VoIP: Spoofing, packet capture, DDoS
Future
PSTN: Being phased out globally
VoIP: The present and future standard