PRI vs. SIP — Which Telecom Technology Is Best for Your Business?

November 28, 2023 7 min read

Cameron Johnson

Cameron Johnson


Voice communication connects people to your business. 

Customers and partners rely on it day in and day out. And you, in turn, rely on business communication tools to keep them connected. These systems cater to the needs of your teams, customers, and partners. When these needs evolve, you must adapt.

Businesses often compare Primary Rate Interface (PRI) and Session Initiation Protocol (SIP) when thinking about agility and scalability. They both help you connect to the telephone network but in entirely different ways.

One is a legacy product from a local telephone company, while the other is much easier to scale. Dive deeper to know which technology best aligns with your needs.

What Is PRI?

PRI is a telecommunication standard that carries voice and data transmissions between a network and a user. It uses physical copper wires to digitally connect your business with the public switched telephone network (PSTN).

PSTN aggregates national, regional, and local telephone operators. Whenever someone calls you, the call enters a private branch exchange (PBX). An on-premises PBX is a private telephone network professionals use within an organization to communicate with external and internal callers.

Network diagram showing primary rate interface
Network diagram showing Primary Rate Interface in an office network (via GCG)

When the call reaches the PBX, an integrated services delivery network line or an analog copper line transmits to the receiver. However, if the receiver is busy, the call will go to a voicemail. This helps businesses prevent callers from listening to a busy tone.

Large organizations and enterprises often use PRI lines to address the challenges of traditional phone service in business. It’s been the backbone of enterprise telephony for many years.

PRI features

Below are some notable features of the PRI telecommunication standard:

PRI requirements

You need PRI-compatible equipment, such as a PRI gateway or a PBX with a PRI card, to interface with digital lines. It can work with analog or private automatic branch exchange systems.

Although PRI allows 23 simultaneous calls, you can increase the capability by adding additional PRI circuits when the number of calls increases.

What Is SIP?

SIP connects your Internet Protocol (IP) PBX to the internet. It lets you make and receive calls over the Internet.

SIP trunking is a scalable way to facilitate voice calls in businesses. Trunking consolidates multiple communication channels into a single virtual connection. It uses resources effectively while connecting to a telephone network.

💡Did you know? SIP is one specific protocol that enables Voice over Internet Protocol (VoIP).

SIP trunking makes voice accessible over the IP network, just like email or web services. It helps businesses move past traditional physical limitations toward IP phone communication. Overall, it makes your phone system digital and offers the flexibility to add and replace lines.

SIP trunking diagram for a business environment for phone connectivity.
SIP trunking diagram for a business environment for phone connectivity

Key features of SIP

Below are some notable features of SIP:

SIP trunking requirements

While switching to SIP trunking, you’re making a physical infrastructure virtual. You’ll need an Internet connection and SIP-compatible PBX, also known as IP PBX.

For desk phones, you’ll need a VoIP phone to connect to your PBX. If you’re using existing traditional phones, get a VoIP adapter. You’ll also need Internet access between your VoIP phones and your PBX server. Older PBX systems might need additional hardware and configuration.

Pros and Cons of PRI

PRI has upsides and downsides. However, these depend on your needs. Dive into some advantages and limitations to get more clarity.

PRI AdvantagesPRI Disadvantages
These PRI advantages stand out to select organizations:

High reliability: PRI uses lines to transmit calls. It provides a remarkable call quality through the plain old telephone system (POTS) technology.
Compatibility: PRI is compatible with existing legacy telephony systems.
Direct extension calling: PRI supports DID and allows businesses to have 50 DID numbers on one PRI circuit.
There are some limitations of PRI-based phone systems:

Requires high investment: Since PRI relies on physical infrastructure and hardware, its setup and maintenance costs are higher.
Lacks scalability: With PRI, you can take 23 concurrent calls and have 100 DID numbers. You can scale it as your call volumes increase, but it requires the physical connection of additional lines.
Takes longer to recover: These systems take a long time to recover if lines are damaged. They need service professionals to have specialized telecom experience.
Uses a fixed location: Moving these systems is tricky, as they’re physically installed at your location. Likewise, phone calls can be traced a little easier than with SIP.

Pros and cons of SIP trunking

If you need a cost-effective voice communication solution that’s easy to scale, SIP trunking is a suitable choice. However, there are advantages and disadvantages.

SIP Trunking AdvantagesSIP Trunking Disadvantages
Cloud-based SIP trunking is one of the more cost-effective options in business communications.

High scalability: You can add and replace lines through software adjustments, which helps you scale voice communication as needed.
Low operational cost: Call charges drop, and voice and data transmission happens on one network. It adds to cost savings while you save yourself from physical line maintenance work.
Better business continuity: When things aren’t in your business favor, you have failover and redundancy options.
The advantages of SIP trunks also come with some added responsibilities.

Dependency on the Internet: Set up a reliable backup network to enable business continuity when outages occur.
Vulnerability to cyber threats: Strengthen your security posture and patch vulnerabilities in a timely manner to deal with security risks. Leverage Secure Real-time Transport Protocol (SRTP) to ensure security.
Replacement of old hardware: Set up a budget to procure new hardware if older systems, such as desk phones, prevail.

PRI vs. SIP Head-to-Head Comparison

FunctionSIP TrunkingPRI
Monthly cost$14.95 per line$16 per line (source: Reddit)
InstallationModerate difficultyHard
Call qualityGreatGreat
FlexibilityOn-premises and cloud-hostedOn-premises only
ScalabilityHighly scalableLimited
Hardware requiredOptionalPBX software requiredOn-premises hardware needed
TechnologyIPSIPSRTP for call encryptionAnalogPOTS lines

Thinking of Migrating From PRI to SIP?

Considering its benefits and features, the decision needle will likely sway toward SIP trunking. When you have made a decision, think about migration. Assess what you need so your team’s communications are seamless

Follow the steps below to make sure your PBX migration is successful.

1. Assess and plan

Assess your voice and data usage to determine the scope of SIP trunking services required. Check if your current network can support SIP. You should upgrade the Internet service and routers and make sure the quality of service matches your available bandwidth.

Then, investigate your PBX. See if it’s compatible with SIP calls or if you need a communication gateway.

2. Choose a SIP service provider

Go for a SIP provider that offers the right balance of cost, reliability, and support. See if it can scale with your business and offer features such as DID, call routing, and other functionalities per your needs.

Case Study: Elkhart Clinic chose Nextiva for SIP trunks to ensure their phones are reliable and they can easily communicate with patients, pharmacies, and providers.

3. Implement

Train your IT staff to manage the migration and troubleshoot any issues that might surface during the process. Then, port existing numbers to the SIP service of the new provider.

When the Adams Publishing Group migrated to Nextiva, they transitioned over 300 phone numbers. Nextiva provided temporary numbers to forward incoming phone calls to Nextiva devices while they were ported successfully.

4. Decide on post-migration support

Make a clear support agreement with your provider for future issues or any changes required after migration. You would need ongoing assistance to make the migration a success.

Choose a SIP provider that provides timely and consistent support. Check if they can train your employees and managers in the new processes and systems.

Nextiva Makes It Easy To Adopt Cloud Communications

With all this talk about PRI and SIP, there might be a better alternative.

Have you considered a cloud-based phone system?

Unlike PRI or SIP, a complete business phone system has everything your team needs to stay in touch and help customers. And it’ll actually lower your infrastructure costs and increase your productivity.

A picture showing the Nextiva cloud phone system

The flexibility and scalability of the cloud encourage its adoption in businesses aspiring to level up with the evolving market. Although you might adore your phone system’s traditional ring, it’s time to part ways and adapt to the needs of your customers and partners.

SIP trunking offers the right construct to amp up your phone system. It’s flexible, cost-effective, and, most importantly, adaptable.

If you’re looking beyond SIP or PRI connection and need an all-in-one business phone service.

Check out how Nextiva can improve your team’s productivity. You could lower your calling costs by up to 60% — that’s a win for everyone.

Cameron Johnson


Cameron Johnson

Cameron Johnson was a market segment leader at Nextiva. Along with his well-researched contributions to the Nextiva Blog, Cameron has written for a variety of publications including Inc. and Cameron was recently recognized as Utah's Marketer of the Year.

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