What Is a SIP Trunk?
If you have heard the term SIP trunk and were not sure what it means, here is the plain-English version, how it is different from the old phone lines, and whether it is something your business actually needs to think about.
As legacy copper lines are retired, SIP trunking has become the standard way businesses connect phone systems to the network, and analysts project the SIP trunking market to keep growing at double-digit annual rates into the early 2030s.
What a SIP trunk actually is
A trunk is telecom-speak for a bundle of phone lines. A SIP trunk delivers those lines digitally over the internet instead of over copper. Your phone system connects to a provider over your data connection, and calls travel as data, the same pipe as your internet.
SIP trunk vs. traditional phone lines
Old analog lines carried one call each, so ten simultaneous calls meant ten physical lines. A single SIP trunk carries many calls at once, measured in channels, and you scale up or down without a technician running new wire. It is cheaper, faster to change, and not tied to copper that is being retired.
Do you actually need one?
Most small businesses do not buy a SIP trunk directly. If you use a hosted cloud phone system, the SIP connection is built in and handled for you. SIP trunks matter most when you already own an on-premise phone system (a PBX) and want to connect it to the modern network. Either way, you keep your existing numbers.
Common questions
Is a SIP trunk the same as VoIP?
They are related. VoIP is any voice call carried over the internet. A SIP trunk is the specific connection that carries those calls between your phone system and the provider. Hosted VoIP has SIP built in behind the scenes.
How many lines is a SIP trunk?
One SIP trunk carries multiple simultaneous calls, each called a channel. You size it to how many calls you make at once, not how many phones you have, so a busy office might need far fewer channels than it has handsets.
Do I need a SIP trunk or a hosted phone system?
If you want the simplest setup, a hosted cloud phone system includes the SIP connection and you never touch it. A SIP trunk on its own makes sense mainly when you are keeping an existing on-premise PBX.
Can I keep my phone numbers with SIP?
Yes. Your existing business numbers port over to the SIP provider, so customers keep reaching you at the same numbers.
Not sure what your phone setup needs? Ask us.
We will tell you whether a hosted system or a SIP trunk fits your business, in plain English, before you sign anything.