What Are SIP Trunks? A Quick Guide

What are SIP Trunks?

Imagine a SIP Trunk as a digital version of the old telephone lines, but instead of using physical wires, it uses the internet to make and receive phone calls.

Now, think of your business’s phone system as a big traditional telephone network with lots of separate lines for making and receiving calls. Each of these lines is like a road that connects your office to the rest of the world. In the past, these “roads” were actual physical wires.

Now, think of SIP Trunks as modern, invisible highways that replace these old roads. Instead of using physical wires, SIP Trunks use the internet to make and receive phone calls. It’s like how you can talk to someone through a video call on your computer or smartphone.

SIP Trunks: A More Technical Explanation

At its core, trunking refers to the practice of allowing multiple calls to share the same telephone line or frequency, instead of dedicating one line per call.

SIP trunks take this concept to the next level by utilising the SIP protocol to transfer calls over data networks, such as the internet or a public switched telephone network (PSTN).

When companies like in2tel discuss SIP trunks, they’re referring to the entire call transfer process using SIP – from your organisation’s PBX system, through their network, and finally to its destination. This can occur across a PSTN or over the internet, offering a versatile solution for all your communication needs.

SIP Channels

A SIP channel is an individual connection within a SIP system. It is essentially a unit of measurement for the bandwidth needed to transfer a call through a SIP connection. The number of channels required depends on how many calls your business needs to handle simultaneously.

The easiest way to think of a SIP channel is like an individual line in a traditional telephone system.

One of the key advantages of SIP channels is their scalability – you can easily add or remove channels as needed, making them perfect for businesses that experience fluctuating call volumes.

SIP Trunks vs VoIP: What’s the Difference?

SIP and VoIP are both protocols used for voice and data communications over the Internet, but they serve different purposes:

  1. VoIP (Voice over Internet Protocol) is a broad term that encompasses all voice communications made over the Internet. It is a technology solely used for voice.
  2. SIP, on the other hand, is a specific protocol that enables VoIP communications to take place, acting as the underlying technology for internet-based voice calls. SIP trunks can also deliver video, messages, and faxes.

Choosing the Right SIP Trunk Provider

A SIP trunk provider offers digital telecommunication services over the internet, such as converting existing telephone systems, providing hosted phone systems, or enabling software applications for communication.

Companies like in2tel specialise in SIP trunks and offer a comprehensive range of communication services, including business landlines, phone systems, and call management software – all powered by SIP trunks for high-quality, low-cost calls and features.

If you’re interested in discussing how SIP trunking can lower your phone bill or improve your communications, feel free to contact in2tel through their live chat, by calling their freephone number at 1800 91 1800, or by emailing sales@in2tel.ie.

The Benefits of SIP Trunks

SIP trunking offers numerous advantages for businesses, such as:

  1. Advanced telephony features: IP telephony enables a vast array of telephony features that can enhance your contact centre, with features that can be quickly implemented and managed by either the provider or the customer.
  2. Unlimited call capacity: With SIP trunking, a single number can handle multiple calls simultaneously, ensuring that customers never hear a busy signal and that your office can manage high call volumes effectively.
  3. Building a presence: Since SIP phone numbers are virtual, you can choose any number without regional restrictions, allowing your business to appear local even when calling from a mobile or fixed location.
  4. Cost savings on calls and line rentals: SIP calls are generally more affordable than traditional phone calls, which can lead to significant savings on both line rentals and call costs.
  5. Easy scalability: SIP channels can be added or removed almost instantly, providing flexibility for businesses facing seasonality, running marketing campaigns, or simply needing to adjust capacity.
  6. Free internal calls: Businesses with multiple sites can benefit from free internal calls between offices, resulting in substantial cost savings.


SIP trunking is a powerful communication tool that offers a plethora of benefits for businesses of all sizes.

From advanced telephony features and unlimited call capacity to cost savings and easy scalability, SIP trunking can revolutionise your business communications.

By choosing a reliable SIP trunk provider like in2tel, you can harness the power of SIP trunking and take your organisation’s communication capabilities to new heights.

About in2tel

in2tel is a telecoms carrier and solution provider with over 17 years of experience in Ireland and the UK. We specialise in delivering affordable, bespoke communication solutions typically found in large-scale enterprises. Our services cater to contact centres, sales and marketing teams, and internal departments across a wide variety of small businesses and SMEs.