SIP Trunking
Explained Simply
Replace your obsolete phone lines with a scalable, cloud-based connection. SIP Trunking connects your business to the world over the internet—cutting costs and boosting reliability.
On-premise or Cloud Phone System
PSTN / Mobile / Landlines
What is a SIP Trunk?
SIP (Session Initiation Protocol) is the standard technology for establishing voice and video connections over a data network. A SIP Trunk is essentially a virtual version of an analog phone line.
Unlike traditional ISDN/PRI lines that require physical copper wires to be installed at your office, SIP trunks work over your existing internet connection. This allows you to connect your Private Branch Exchange (PBX) to the Public Switched Telephone Network (PSTN) without hardware restrictions.
Two-Way Communication
Handles both inbound and outbound calls simultaneously.
Elastic Scalability
Add unlimited channels instantly during high traffic periods.
Secure Transmission
Calls are encrypted using TLS and SRTP protocols.
Hardware Independent
Works with IP-PBX, softphones, and legacy systems (via gateways).
SIP Trunking vs. Traditional ISDN/PRI
Why businesses are switching to SIP en masse.
| Feature | SIP Trunking | ISDN / PRI |
|---|---|---|
| Setup Time | Instant (Minutes) | Weeks or Months |
| Cost Structure | Pay-per-channel or minute | Expensive fixed monthly rental |
| Scalability | Unlimited, Instant | Limited to 23/30 channels per wire |
| Hardware | None (Virtual) | Physical Cards & Wiring |
| Location | Work from anywhere | Tied to physical office |
| Redundancy | Auto-failover to mobile/cloud | Line down = No calls |
Why Your Business Needs
SIP Trunking
It's not just about cheaper calls. It's about building a communication infrastructure that grows with your business.
Cost Savings up to 60%
Eliminate expensive line rentals and reduce international call rates significantly.
Global Presence
Provision local phone numbers in 190+ countries instantly, without physical offices.
Unified Communications
Support voice, video, and messaging on a single network backbone.
StartACall SIP Features
Common Questions about SIP
Do I need to replace my current PBX?
Not usually. If you have a modern IP-PBX (like Asterisk, 3CX, Avaya IP Office), it supports SIP natively. If you have an older analog PBX, you can use a VoIP Gateway device to convert the SIP signal to analog, extending the life of your hardware.
How much bandwidth does a SIP trunk require?
A standard non-compressed call (G.711 codec) uses about 85-100 kbps (upload and download). We also support the Opus codec, which provides HD quality at lower bitrates, adapting to your network conditions.
Is SIP Trunking secure?
Yes, when configured correctly. StartACall uses TLS (Transport Layer Security) to encrypt signaling and SRTP (Secure Real-time Transport Protocol) to encrypt the audio media, preventing eavesdropping.
What happens if my internet goes down?
This is a major advantage of SIP. We can configure automatic failover forwarding. If your office internet drops, calls can be instantly rerouted to mobile phones, a different office, or a voicemail system in the cloud.
Ready to modernize your phone system?
Get enterprise-grade SIP trunking with pay-as-you-go pricing.