SIP trunking (Session Initiation Protocol trunking) is a method of sending voice and other unified communications services over the internet, instead of using traditional phone lines.
What it Does
- Connects your business phone system (PBX) to the internet.
- Lets you make and receive calls using VoIP (Voice over IP) instead of old-school landlines.
Why It’s Called a "Trunk"
- In traditional telephony, a "trunk line" was a single line that carried many phone calls.
- SIP trunking is the modern, digital version of that — using internet bandwidth to carry multiple calls.
What You Need
- A SIP provider (also called an ITSP – Internet Telephony Service Provider)
- An IP-enabled PBX (or a regular PBX with a gateway)
Benefits
- Cost savings – lower rates than traditional phone services
- Scalability – add or remove lines easily
- Flexibility – works anywhere you have internet
- Unified communications – integrate with video, messaging, and other tools
Common Use Case
Businesses replacing their expensive PRI (Primary Rate Interface) lines or analog lines with SIP trunks to modernize and save money.