sip trunks vs pri

SIP Trunk vs PRI: Which Is Best?

If you want to learn which technology between SIP trunks and PRI phone systems suits your needs, this is the right place. Knowing the difference between a SIP trunk vs PRI will help you make an informed decision when choosing the best communications technology for your business.

This article may also help SIP trunk sellers better explain to clients the differences between a SIP trunk vs PRI. But first, what’s the difference between the two technologies, and what are the pros and cons of each?

SIP Trunks vs PRI: What’s The Main Difference?

Session Initiation Protocol (SIP) is a system that came into being with the rise of Voice Over Internet Protocol (VOIP). It can handle both voice and data transmissions using virtual connections.

On the other hand, Primary Rate Interface (PRI) uses dedicated lines (physical lines) or physical T1 transmission technology to provide voice transmission via copper lines in buildings.

One similarity between SIP trunk vs PRI is that both of them connect businesses to the Public Switched Telephone Network (PTSN).

The two technologies have three major categories of differences;

  • Connection – a SIP trunk uses a virtual connection through a network while PRI uses a physical connection through a PRI Circuit
  • Transmission – SIP trunk calls are transmitted using data packets on a virtual network, while PRI calls are transmitted through physical circuits
  • Scalability – SIP trunking is limited only by your bandwidth, while PRI is limited by the number of wired phone lines

Since both PRI and SIP trunking compete in the phone technology industry, they both have distinct advantages and disadvantages.

Related: SIP Phone Service: Does Your Business Need It?

Advantages of a SIP Trunk


A SIP trunk is cost-effective. The traditional phone service subjects you to different costly charges for local and international calls. However, SIP trunking is cheaper since it’s billed on a per-user basis. This billing enables you to predict your monthly bill. A business using SIP trunks can expect a 30-40% decrease in costs.


If IP phones don’t complete the calls due to a loss of Internet connection, SIP trunks make failover to mobile phones easy and fast. SIP uses VoIP apps that employees can install on their mobile devices. Thus, your employees are always connected to your organization’s communication systems, enabling your employees and clients to keep in touch even if there’s no data connection.


SIP trunks are easier to manage due to their easy to use administrative portals.

Cloud-Based and Mobility

If a SIP trunk is part of a Unified Communications implementation (UC), its configuration is done in the cloud. Because it’s in the cloud, SIP trunks have excellent mobile features.


There are many integrations available for SIP trunk that increase collaboration and productivity. For instance, the integrations to multimedia communications. You can also combine a SIP trunk with a PRI in a hybrid line enabling you to get the best of both technologies.


Phone number flexibility – with SIP trunking, you maintain your existing phone number even if you move office. This feature helps to reduce the number of PBX’s (Private Branch Exchange System) you need to maintain while maintaining your existing phone number.

Related: PBX, Hosted PBX and SIP Trunking: What’s the Difference?


SIP trunks are good if you want to retain your phone numbers while growing your business. You can easily add phone lines when the need arises and remove them at will. SIP trunking enables your organization to grow across multiple geographic locations. Since it combines voice and data into one connection, it enables your organization to be connected with remote workers. Also, when relocating, SIP trunking allows you to take your phone lines with you.

SIP trunking makes it possible to expand your communications network without the physical infrastructure. Traditional phone services require the installation of new phone lines. However, SIP makes it easier for you to expand by only requiring you to connect your devices to your data connection and not requiring the dedicated phone lines like traditional phone service.

Advantages of PRI

Independent of Bandwidth

The biggest advantage of PRI is that voice calls do not rely on bandwidth or data connections. A connection using physical lines will do just fine. This also means that voice quality is not sensitive to shared data bandwidth.I

f your business does not have access to high-speed data connections, PRI is a reliable option for your voice communications. This means that businesses in places without high-speed data connections can still get high-quality telecommunications systems with PRI.

Call Quality

 PRI calls can be established easily and have a superior voice quality than Public Switched Telephone Network (PSTN) channels. The higher voice quality is due to the end to end digital PRI connection and the dedicated physical lines.


 If a second PRI Circuit is added for failover purposes, you get a redundant system that offers improved reliability.


PRI may work with some IP-based phones to support older technologies such as fax machines. You can use PRI links for multiple communication features such as data transfer and fax transmissions. You can also use these features at the same time without noticeable effects on quality.


PRI lines are more secure and reliable. Since PRI data is transmitted via physical lines and doesn’t use the Internet, PRI lines can’t be hacked or easily tapped. Furthermore, in case of technical failure, troubleshooting is easier.

Certain Call Features

PRI lines have a feature called Direct inward dialing (DID). This feature enables businesses to publish different telephone extension numbers for their departments, making it easier for customers and stakeholders to communicate with the departments directly. 

When these departments call clients, the clients receive that specific extension number on their caller ID. They can then use the number to reach out to the said department directly without going through customer support.

PRI lines also have an Automatic Call Distribution (ACD) feature that automatically sends calls to the next free line when the called line is busy. The customers’ calls get answered, and your organization gets more business.

Disadvantages of SIP Trunk

  • SIP Trunk requires fast bandwidth for quality voice calls.
  • Due to connections with the Internet, you must ensure that you install firewalls and other network security protocols to prevent cyber-related crimes.
  • You must have a compatible phone system,

Disadvantages of PRI

  • PRI is very expensive to install and upgrade, so the monthly phone service plans may exceed IP-based phone services, especially for long-distance calls.
  • Telephone companies that sell PRI typically require long term contracts for local and long-distance calls.
  • It’s slow to scale due to its reliance on physical infrastructure.
  • PRI security risks include call interference.
  • PRI does not offer mobile failover in case of failure or emergency.
  • There’s a shortage of expert PRI technicians due to the increased adoption of SIP.

Which Is Best For You?

When choosing between SIP trunk vs PRI, you need to make sure you do due diligence. You should especially keep in mind the following factors;


SIP is cheaper than PRI. However, if you do not need an advanced phone feature like integrated messaging, an existing PRI system could be your best option.

Network Security

If your organization doesn’t have good network security, adding VOIP to your network may risk your data and information being stolen over the Internet.


Since SIP trunking is flexible, PRI may not be the right option if your organization expands quickly. With PRI, you have to buy an additional circuit of 24 lines when you want to expand. It also takes more time to upgrade PRI systems, usually weeks.


PRI may be reliable, but SIP can become reliable with the advent of high-speed Internet connectivity and the right vendor.

Wrapping Up

This article has covered the differences between a SIP trunk vs PRI. In summary, a SIP trunk uses virtual connections to handle both voice and data transmissions. On the other hand, the Primary Rate Interface (PRI) uses dedicated copper lines to provide voice transmission in buildings.

They both have their advantages and disadvantages. With SIP networks, you can expect easy management, cheaper costs, increased flexibility, and even integration with multimedia communications. For PRI, you can expect voice calls that don’t rely on internet connectivity and are more secure. PRI also enables faxing, which can be important to organizations that depend on faxes, e.g., law firms.

When choosing a side in the SIP trunk vs PRI debate, examine your needs and take the time to compare the advantages and disadvantages of a SIP trunk vs PRI. Ready to get started with SIP trunking? SIPTRUNK can help.