Practical guide
SIP trunking or Cloud PBX: which one does your business need?
Both are IP telephony and both give you Colombian numbers. The difference is who runs the phone system. Here’s how to decide, and how many channels you need.
Hablame TeamPublished 4 min read
The difference in one sentence
With a SIP trunk, you run the phone system and the carrier gives you the connection to the phone network. With a cloud PBX, the carrier gives you the whole phone system in the cloud and you just connect people and devices.
Everything else follows from that: who configures extensions and menus, who maintains the equipment, how customized the setup can be and what you need in place before you start.
What a SIP trunk is
A SIP trunk is an IP voice connection that carries your PBX’s calls to the public phone network using the SIP protocol. It replaces physical lines: each channel carries one concurrent call, and they all travel over the same data connection.
- Works with SIP-based IP PBXs and contact center platforms, such as Asterisk.
- Authenticates by IP address or by registration with credentials.
- Carries your Colombian local numbers from any region, your toll-free lines and, if you need them, international numbers.
For critical operations, such as a contact center or multiple sites, we design the security and continuity of your trunk with you: a session border controller (SBC) that filters traffic and shields your PBX from toll fraud, plus backup routes. Assessed for each project.
What a cloud PBX is
A cloud PBX is a phone system that runs in the carrier’s cloud instead of on hardware in your office. It does what a business phone system does, and you manage it online.
- Per-person extensions with voicemail, transfers and internal dialing across sites.
- A softphone on the computer and an app on the mobile, at the office or at home.
- Auto attendant, queues and time-of-day rules you adjust from the portal.
All you need is a stable internet connection at each site or desk. Exact features are confirmed in the proposal for your company, and if you’re switching providers, we migrate your phone system.
How to decide: five questions
1. Do you already have an IP PBX that works well?
If so, a SIP trunk lets you keep it and retire your physical lines without changing how your team works. If your system is old or nearing end of life, it’s a good time to look at a cloud PBX.
2. Who will manage your telephony?
With a SIP trunk, your IT team or integrator manages the PBX. With a cloud PBX, you adjust extensions, hours and menus from the portal, and the carrier maintains the platform.
3. Do you run a contact center?
Contact center platforms usually have their own call engine and need a SIP trunk sized for their inbound and outbound traffic.
4. Does your team work from several sites or from home?
A cloud PBX puts every site and remote worker on one phone system, with the same extension on the desk phone and the mobile app. You can do this with your own PBX too, but it depends on how your network is connected.
5. How much do you need to customize?
With your own PBX, customization is unlimited. A cloud PBX gives you the platform’s feature set, which covers what most businesses need without extra development.
Rule of thumb: if you have a PBX or a contact center, start with a SIP trunk; if you don’t want to buy or maintain hardware, start with a cloud PBX.
How many concurrent calls you need
Whichever you choose, you’ll subscribe to channels: each channel is one call at a time. The number that matters isn’t how many calls you make a day, but how many overlap at your busiest hour.
The calculator below gives you an estimate from your peak-hour calls and their average length. Bring the result to the conversation with us: we refine it with your real data in the proposal.
Calculator
Work out how many SIP channels you need
From the calls in your busiest hour and their average length, we estimate how many simultaneous calls your trunk should carry.
Indicative estimate only; not a quote or a technical commitment.
How we calculate it
Traffic in Erlangs = busy-hour calls × average length in minutes ÷ 60. One Erlang is one line busy for the whole hour.
Channels come from the Erlang B model: the smallest number of channels that keeps the probability of a call finding no free line at or below the level you chose.
The model assumes a call that finds no channel is lost rather than queued. If your operation uses queues, outbound campaigns or very sharp peaks, sizing changes, and we review it with you.
When it makes sense to use both
It isn’t all-or-nothing. Many companies run a cloud PBX for their offices and a SIP trunk for the contact center, or a trunk at headquarters and a cloud PBX for subsidiaries that need autonomy.
If your company uses Microsoft Teams, also see Microsoft Teams calling. And if you’ll take free calls from across the country, the guide Getting a toll-free number explains how to route them to either option.
What you need either way
- A stable internet connection. Voice is sensitive to outages and congestion; good upload capacity makes a real difference. See dedicated internet access.
- A plan for when something fails. Forwarding calls to mobiles or another site is the simplest contingency.
- Your numbers. Decide which local and 01 8000 numbers you need and in which regions.