Voice over Internet Protocol

VoIP (Voice over Internet Protocol) is the technology that transmits voice calls over IP networks — including the internet — instead of traditional analog phone lines or digital circuits. VICIdial is a VoIP-native platform built on Asterisk, using IP-based SIP signaling and RTP media streams for all call handling.

How It Works in VICIdial

VICIdial’s entire telephony stack is VoIP-based. Outbound calls are placed over SIP trunks to VoIP carriers, who convert the call to PSTN (traditional phone network) for delivery to the called party. Agent phones connect to the VICIdial server using SIP, PJSIP, IAX2, or WebRTC — all VoIP protocols.

Voice audio is digitized using a codec (such as G.711 or G.729), packetized into RTP streams, and transmitted over UDP. The quality of VoIP calls depends on network characteristics: latency (ideally under 150ms), jitter (variation in packet arrival times), and packet loss (ideally under 1%). VICIdial servers should be hosted on networks with QoS guarantees for voice traffic.

VoIP enables features impossible with traditional telephony: unlimited geographic flexibility for agents, easy server scaling, call recording at the software level, and real-time analytics through the Asterisk Manager Interface.

Why It Matters

VoIP is what makes VICIdial economically viable as an open-source call center platform. Traditional PBX systems require expensive hardware and per-line charges. VoIP eliminates hardware costs and reduces per-minute calling rates by 50-80% compared to traditional telephony. A single VICIdial server can handle hundreds of concurrent calls over a standard internet connection.

The shift to VoIP also enables distributed call centers with remote agents worldwide, all connecting to a centralized VICIdial cluster. See the VICIdial cost guide for detailed VoIP cost comparisons and the VICIdial setup guide for network requirements.