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SIP vs PRI - An In-Depth Comparison

Updated: July 20, 2020
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If you’re looking to upgrade your business phone system or you’re just starting a business and you’re looking for modern communication solutions, you’re probably navigating in what may seem like an ocean of acronyms, none of which make sense to you. 

But even though the communication industry is complicated and rich in jargon, your choice really boils down to two options - Primary Rate Interface (PRI) phone systems, or traditional telephony, and voice-over-IP (VoIP) phone systems which are delivered over Session Initiation Protocol (SIP), or cloud telephony. 

Many enterprises are switching from PRI phones to SIP because cloud communications are cheaper and they offer more features and functionalities than traditional phones. However, other companies are choosing to keep their legacy phone systems, while a small percentage of businesses use hybrid communication solutions that unite legacy and IP phones into a single system. 

So, what’s the difference between SIP and PRI? And more importantly, is SIP trunking a better fit for your needs than PRI trunking? Read on to find out. 

What is SIP Trunking?

Session Initiation Protocol (SIP) is a telephony network protocol that supports the transmission of voice calls and other types of multimedia communication as data. Even though SIP is a phone technology, you can use it to hold or join video conferences, send SMS messages, transfer files, and more. 

In the telephony world, trunking means a dedicated line. SIP trunking equipment is usually hosted and maintained by your service provider. SIP completely eliminates the need for traditional phone infrastructure, so you no longer need circuits or expensive upgrades. 
SIP trunks are completely virtual, so you can deploy them without additional hardware investments. You can use SIP for voice without having to invest in a PBX because many service providers offer hosted PBX.

What Is PRI trunking? 

PRI is a telephony technology that has been widely used to transmit voice communications since the 1980s. This technology is an interface standard used on an Integrated Services Digital Network (ISDN) to deliver multiple voice lines into a company’s Private Branch Exchange (PBX) via one physical line called a circuit. 

Many consider PRI an “old-school” telephony system because it uses physical hardware and requires servicing from a telco company for deploying, troubleshooting, and upgrading. 

And that’s because PRI is a service carried on T1 trunk lines from the telco central offices to your location. Most enterprises have their ISDN PRI circuits as fractional T1 lines. A T1 line supports voice and data via 24 digital channels.

The Pros And Cons Of SIP And PRI

Even though they’re both good communication technologies, both SIP and PRI have their pros and cons. 

SIP Pros 

  • Cheaper - SIP is much cheaper than PRI. Costs savings vary from company to company, but SIP can be as much as 40% cheaper than PRI phones. Since you’re using the Internet to make your calls, both local and international calls are cheaper with SIP. 
  • Easy Management - SIP comes with intuitive administrative portals that enable you to manage your communication system. You don’t have to call a support technician to make changes in the system, you can make them yourself with a few simple clicks. 
  • Easy To Scale - You can scale SIP systems with ease. Adding more lines to your SIP trunk usually involves making an online request with your provider or upgrading your hosted service subscription. 
  • Simple Support - SIP offers simple support for multiple business locations and remote workers. 
  • Modern - SIP may include rich mobile features and supports mobile-first design. 

SIP Cons 

  • Requires An Internet Connection - SIP requires an Internet connection. When your Internet is down, your telephony system is down as well. 
  • Needs Firewall Protection - SIP needs cybersecurity, such as firewall protection, to keep your data safe. 
  • Varied Services - SIP services are not standardized. As a result, the quality and extensibility of your SIP service can vary for different providers. 

PRI Pros 

  • Self-Contained - PRI does not require an Internet connection in order to transfer your data. Your telephone lines will be up and working even if your Internet connection is down. 
  • High-Quality Calls - PRI is not subject to network interference, so it offers high-quality calls. 
  • Secure - PRI data travels through a dedicated line that’s not exposed to the Internet. As a result, the data is not exposed to cybercrime risks. 

PRI Cons 

  • Expensive Implementation And Maintenance - PRI is expensive to implement and manage. You might need to employ a communication specialist or to hire a specialist to upgrade or maintain the system. 
  • Slow To Scale - PRI systems are slow to scale. You need to call the PRI provider to send someone on-site and implement another PRI circuit. This process can take days or even weeks. 
  • Long-Distance Calls Might Cost Extra - Long-distance calls might cost extra when you use a PRI, depending on your service contract. 
  • Limited Capacity - PRI has a limited capacity that’s measured in circuits. Each circuit offers 24 lines, so you’ll have to invest in another circuit if you need more lines. And it doesn’t matter if you need only one or two extra lines, you’ll still have to purchase a whole new circuit.

Which One Should You Choose? 

Here are a few things you should consider when choosing between SIP trunking vs PRI trunking:

  1. Cost - SIP is usually much cheaper than PRI. SIP is easy to implement and maintain. But it’s probably even more important that SIP is cheap to scale and improve. If you might scale your business in the future, add more features to your existing communication scheme, or perform long-distance calls, then SIP is the right system for you.

    However, if your business is small and will probably remain so for the foreseeable future, and you don’t use advanced phone features, then a PRI system might do the trick. 
  1. Security - PRI systems are considered more secure, even though copper cabling can be subjected to a large number of security risks, such as interference or interception, just as easy as online systems. If your organization deals with highly sensitive data that are transmitted over the phone, then PRI might be the right system for you. 

    However, it’s worth noting that a SIP system that’s protected with a firewall and data encryption might be just as safe, if not even safer, than a PRI system using copper wires. 
  1. Reliability - Even though the copper cables PRI uses are considered reliable, they can still be subjected to degradation due to weather interference, vandalism, or an aging infrastructure. And when your phone lines go down, it might take days or even weeks to get them back up and running. 

    Now, SIP only works as long as you have a stable Internet connection. That might seem like a flimsy thing, but service providers who combine SIP services with fiber-optic Internet guarantee that their Internet - thus your SIP telephone system - will be up 99.99% of the time.  

Contact a support specialist and examine the communication solutions available for your company. 


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