And then you start looking.
The comparisons are multiplying, and so are the promises. The comparisons are multiplying, each claiming reliability, flexibility and savings.
But which one really meets your needs?
That’s why we’ve written this guide: to bring a little clarity to a subject that has all too often been made opaque.
Together, we’re going to decipher what a SIP Trunk is, how it works and, above all, how to install it in your environment, without starting from scratch.
Points to remember :
- Trunk SIP links traditional and cloud telephony, replacing physical lines with a more flexible, scalable Internet connection.
- It reduces fixed costs while increasing the number ofsimultaneous calls, without changing your existing infrastructure.
- This technology offers centralized, mobile telephony, suitable for distributed teams, telecommuting and multi-site businesses.
- Trunk SIP makes it easy to migrate to IP telephony before the end of the PSTN network, without disrupting service or completely overhauling the system.
What is a SIP Trunk?
A SIP Trunk( Session Initiation Protocol) is a virtual link between your telephone switchboard and the global network.
Instead of using copper cables or traditional fixed lines, it transmits voice, video and messages via the Internet.
The result: less physical infrastructure, greater flexibility, and IP telephony that adapts to your needs in real time.
In practical terms, Trunk SIP acts as a bridge between your internal telephone system and the global network.
The role of the SIP protocol
The SIP protocolprotocol is the language your equipment speaks to establish, manage and terminate calls.
It coordinates exchanges between your equipment: who calls, who answers and how the communication flows.
It’s how different devices, applications or servers understand each other, regardless of brand or location.
Without this protocol, IP telephone communication would be nothing more than a set of sounds lost in the network.
SIP, Trunk SIP and IP telephony: no more confusion
IP telephony is the technology that enables calls to be made over the Internet.
SIP is the rule book: the protocol that orchestrates the exchanges.
And what about the SIP Trunk? This is the connection that allows your calls to leave your company and reach the rest of the world.
To summarize:
VoIP = the method, SIP = the protocol, Trunk = the virtual line.
In brief
| What it is | What it changes |
|---|---|
| A SIP connection replaces physical lines with an Internet connection. | Less equipment, lower costs, greater flexibility. |
| The SIP protocol manages exchanges between your equipment. | Your calls go through everywhere, even from multiple locations. |
| SIP Trunk connects your switchboard to the global network. | Your communications become simultaneous and scalable. |
Why companies are migrating to Trunk SIP
Every company has its own reasons for changing telephony, but the starting point is often the same:
costs rise, maintenance becomes a headache, and traditional systems no longer keep pace with the company.
Trunk SIP doesn’t change everything.
On the contrary, it simplifies what already exists.
Reduce costs without sacrificing quality
With conventional telephony, every line added puts a strain on the budget.
Cabling, subscriptions, maintenance: it all adds up.
Trunk SIP enables multiple calls to be routed over a single Internet connection, reducing fixed costs.
Many companies are switching from dozens of lines to a single IP link – lighter to manage and much more flexible.
Simplify maintenance
Maintaining an analog system can quickly become a pitfall.
Between technical interventions, slow updates and parts to be replaced, the hidden costs mount up.
With Trunk SIP, everything is centralized in a single software interface.
Settings can be made remotely, with no need for travel or service interruption.
Telephony becomes dynamic: remote updates, with no need for additional wiring or hardware.
Quick tip
If you’re still spending time contacting your operator for every line change, Trunk SIP can cut these steps by a factor of ten.
New numbers, transfers or queues can be adjusted from a web console in just a few clicks.
Adapting to team mobility
Telecommuting and the distribution of teams over several sites have made the concept of a fixed workstation obsolete.
Today, a company number must follow its user.
With Trunk SIP, employees connect from a computer, IP phone or softphone.
Their number remains the same, wherever they work.
For a customer service or sales team, this flexibility changes everything.
Compatibility and seamless integration
One of the major advantages of Trunk SIP is its universal compatibility.
It integrates with most telephone switchboards(IPBX, PBX, or cloud-hosted systems**) without modifying the existing system.
In other words, there’s no need to start from scratch.
Trunk fits in with your existing infrastructure, while paving the way for all-IP telephony.
Scalability without constraints
Gone are the days when you had to order new physical lines to expand a call center.
Trunk SIP lets youadd or remove channels according to workload.
Peak activity? You can temporarily increase capacity.
An off-peak period? Reduce it, without unnecessary fixed costs.
This flexibility is particularly attractive to seasonal businesses, fast-growing start-ups and expanding commercial departments.
In practice: migration in figures
| Objective | Before Trunk SIP | With Trunk SIP |
|---|---|---|
| Number of lines required | One per call | A single IP link for multiple calls |
| Average monthly cost | High (multiple subscriptions) | Reduced (all-inclusive) |
| Maintenance | Manual, local | Centralized, remote |
| Scalability | Limited | Instant |
SIP Trunk doesn’t just move voice over the Internet.
It transforms telephony into an agile service, ready to grow with your business.
When to adopt a SIP Trunk
Adopting a SIP Trunk is often a question of good timing.
Technology only makes sense if it solves a real problem.
And in most companies, that moment always arrives.
Modernizing an aging system
You may still have a PBX switchboard that works properly, but which nobody wants to touch any more.
Every upgrade costs time, every breakdown mobilizes a technician, and every new line is like a surgical operation.
Trunk SIP integrates easily into this structure.
It replaces physical lines without dismantling the rest, while breathing new life into your telephony infrastructure.
It’s a smooth transition to IP telephony, without breakage or forced migration.
Anticipating the end of the PSTN
The Public Switched Telephone Network (PSTN) is living out its final years.
Operators have already begun to shut down lines, and businesses that remain on this model may soon find themselves isolated.
Switching to Trunk SIP means anticipating rather than enduring.
It keeps you connected, compatible and ready for future network developments.
Managing sales expansion
A growing company can be recognized by one simple detail: the telephone rings all the time.
New customers, new offices, new teams: everything is speeding up, and the telephone system has to keep up.
Trunk SIP supports this growth without pain.
Simply add virtual channels to absorb the increase in calls.
No physical limits, no commissioning delays: capacity adjusts to demand.
Opening up your business internationally
Deploying a presence in several countries often requires local numbers and a consistent professional image.
With a SIP Trunk, it’s possible to obtain numbers in over fifty countries while maintaining a single central management point.
International calls are routed via the Internet, avoiding the usual interconnection costs.
Your teams call as if they were on the spot, while your customers feel as if they’re calling a local company.
In brief
| Situation | The benefits of SIP Trunk |
|---|---|
| Aging PBX system | Smooth migration to IP telephony without replacing everything |
| End of the PSTN network | Service continuity and future compatibility |
| Rapid growth | Instant addition of call channels |
| International expansion | Local numbers in several countries, centralized management |
Guide : How to set up a SIP Trunk connection
Setting up a Trunk SIP is not a technical task reserved for engineers.
If done properly, installation can be quick and almost invisible for teams.
It’s all about preparation and the right support.
1. Assess your needs
First of all, you need to understand your current usage.
How many simultaneous calls does your company handle?
How many users need a dedicated extension or number?
This assessment is used to correctly size the capacity of the SIP Trunk.
Too small, and it creates blockages; too large, and it becomes unnecessarily expensive.
The objective is to get the measurement right.
2. Choosing the right architecture
Once you’ve identified your needs, it’s time to decide on the structure.
There are two possible scenarios:
- A 100% IP solution, ideal for companies that have already switched to cloud telephony.
- A hybrid solution, linking your old analog PBX to the Internet via a gateway.
This flexibility makes it possible to gradually integrate Trunk SIP without interrupting service.
3. Configure SIP Trunk
Next comes the technical configuration:
the Trunk is connected to your IPBX (local or hosted in the cloud) and associated with your existing numbers.
This is where your telephony really becomes IP.
A customer’s call no longer travels over the traditional telephone network, but now transits via the Internet with the same clarity, if not better.
4. Connect equipment
Your telephones, softphones or applications must recognize the new system.
A simple configuration is usually all that’s needed: server IP address, SIP IDs and communication ports.
Modern solutions make this step intuitive.
With just a few clicks, your agents can make their first call via Trunk SIP.
5. Test and refine
Before going fully live, it’s crucial to check call quality, latency and network stability.
These tests are used to adjust Trunk parameters (codec, bandwidth, routing rules).
Once validated, the system is ready to welcome the whole company.
6. Training and supporting teams
The success of a migration depends on more than just technology.
Users need to understand how to use the new tools, and how to manage their transfers, messages and queues.
A short training session is often all that’s needed to dispel any apprehensions.
This is where a technical partner capable of combining simplicity, human support and compliance comes in.
Kavkom, a French provider of cloud telephony solutions, supports companies every step of the way:
needs analysis, Trunk SIP configuration, testing, and team training.
Commissioning is entirely online, with no hardware, no commitment, and responsive French-speaking support.
Trunk SIP FAQs
What’s the difference between SIP and Trunk SIP?
SIP(Session Initiation Protocol) is the language that enables two telephony systems to communicate with each other.
SIP Trunk is the virtual link that carries these communications.
You could say that SIP talks, and Trunk makes the voice travel.
Is Trunk SIP replacing VoIP?
Not really.
VoIP is the method of delivering voice over the Internet, while SIP Trunk is the connection that links your system to the outside world.
The two complement each other: without Trunk, VoIP remains internal; without VoIP, Trunk has nothing to carry.
Do I need an IPBX to use Trunk SIP?
Yes, in most cases.
Trunk SIP connects to your IPBX or to a cloud-hosted switchboard.
This is the system that distributes incoming and outgoing calls to the right users.
If you already use a cloud switchboard, the IPBX is simply hosted by your provider.
Can I keep my existing numbers?
Absolutely.
Number portability is a standard step in the installation of a SIP Trunk.
You keep your current numbers, which makes for a smooth transition, with no loss of reference points for your customers.
How many simultaneous calls can a SIP Trunk handle?
As many as you decide.
Each channel corresponds to one simultaneous call; simply add or remove channels as your business requires.
This is what we call scalable telephony: the ability to instantly adjust the number of channels according to demand.
Does Trunk SIP work internationally?
Yes.
It allows you to have local numbers in several countries and centralize them in a single system.
This is particularly useful for companies operating in different markets, who want local contact without having to multiply the tools.
Conclusion: understand before you migrate
Trunk SIP links traditional telephony with cloud telephony.
It reduces costs, handles more calls simultaneously and preserves your existing infrastructure.
And when this transition is accompanied by a human partner, able to guide you without jargon or delays, you finally have the missing piece of the puzzle to modernize your company’s telephony.
