voice over IP

Voice over IP converts analog voice signals into digital packets and sends them across Internet Protocol networks instead of through traditional switched telephone circuits. A microphone input is sampled, compressed, and wrapped in IP datagrams; the receiving end unwraps, decompresses, and converts the signal back to audio. This works over any network that handles IP traffic: the public Internet, private LANs, WANs, or dedicated leased lines.

The core advantage is cost. Circuit-switched telephony reserves a dedicated 64 kbps channel for the duration of a call; VoIP uses bandwidth only when voice data actually exists, typically consuming 8 to 64 kbps depending on codec choice. Codecs like G.711, G.729, and Opus trade compression ratio against processing overhead and call quality. A business can eliminate separate telephone and data infrastructures, running both over a single managed network.

Practical deployment and constraints

VoIP systems require synchronized clocking between endpoints and low latency: one-way delay should stay below 150 milliseconds or conversation becomes uncomfortable. Packet loss of even 1 to 2 percent becomes audible as dropouts or artifacts. Jitter buffers compensate for variable packet arrival times, but add latency themselves. Networks must prioritize voice traffic through Quality of Service mechanisms, or VoIP calls degrade when data transfers consume bandwidth.

Common implementations run on Session Initiation Protocol (SIP) for call setup and signaling, with Real-time Transport Protocol (RTP) carrying the actual voice stream. Enterprise systems use proprietary PBX software or hosted SIP trunks; consumer VoIP relies on broadband ISP connections plus adapters or softphones. Power outages are a liability: traditional phone lines carry power in the handset; VoIP phones need local power supplies.

Security is a persistent concern. Eavesdropping, toll fraud, and denial-of-service attacks target both signaling and media streams. Encryption with SRTP and TLS helps, but incomplete industry standardization leaves gaps. Regulatory requirements for E911 service and call recording vary by jurisdiction, adding compliance complexity absent from legacy telephony.