VoIP Explained: How Calls Travel Over the Internet

VoIP stands for Voice over Internet Protocol. Instead of using a dedicated telephone line for each call, your voice is turned into small data packets that travel over the internet like any other traffic. It is the technology behind office phone systems, many mobile calling apps and browser tools such as the Globfone WebPhone.

What happens during a VoIP call

1. Capture. Your microphone records sound as an analogue signal.
2. Encode. A codec such as Opus compresses it into digital packets.
3. Signal. Software (SIP is a common protocol) sets up the call and tells the other side how to connect.
4. Transport. Packets travel across the internet, usually using UDP because speed matters more than perfect delivery.
5. Bridge. A gateway converts the call to the traditional phone network when you dial a normal number.
6. Decode. The receiving side reassembles the packets and plays them in order.

VoIP, SIP and WebRTC

These terms overlap. VoIP is the idea. SIP is a signalling language used by many VoIP systems, including Globfone Premium, where you can use SIP credentials on other devices. WebRTC is a set of browser features that makes VoIP possible without plug-ins; read more in our WebRTC article.

What decides the call quality

• Latency. Delay above roughly 150 ms makes conversation feel awkward.
• Jitter. Packets arriving unevenly sound like choppy audio.
• Packet loss. Lost packets create gaps. Wired connections lose fewer than busy Wi-Fi.
• Route quality. The carrier behind the call matters. This is one reason premium routes sound clearer than low-cost ones.

Pros and cons

Advantages: low cost for international calls, calling from any device, features such as recording and call history, and no dedicated hardware. Disadvantages: it needs an internet connection, quality depends on the network and emergency calling may not work the way it does on a mobile network. Never rely on VoIP as your only way to reach emergency services.

Trying it

The simplest test is a short browser call. Read how to make free online phone calls and compare costs in cheap international calling options.

VoIP in daily life

• Office phone systems and call centres run on VoIP and let staff use their number from home.
• Mobile operators carry your voice as VoIP on 4G and 5G networks (VoLTE and VoNR).
• Browser phones such as the Globfone WebPhone use WebRTC, a browser form of VoIP.

Questions

Is VoIP secure?

Modern VoIP encrypts the voice stream and the signalling. The weak points are usually passwords and misconfigured systems, so use strong credentials.

Does VoIP work during a power cut?

Not unless the router and modem have backup power. Keep a mobile phone for emergencies.

Can I keep my old number?

Many VoIP providers support number porting, but it depends on the country and the provider.