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PRI vs. SIP trunking:
what's best for
your business?

Author: Satta Sarmah Hightower

Businesses must be more agile and able to quickly respond to the continually evolving needs of their customers and partners. Voice communications play a critical role in accomplishing this goal, which makes the phone service that companies rely on for internal and external communications a key business enabler. Primary rate interface (PRI) and voice over internet protocol (VoIP), also often referred to as session internet protocol (SIP) trunking are two communication solutions widely used by companies today. Each approach comes with its own benefits, depending on your company's needs.

Here's what you need to know about PRI vs. SIP trunking and how each solution can help your business.

PRI vs. SIP trunking: what's the difference?

With PRI, when a call comes into a business, it goes through a private branch exchange (PBX) system that allows employees to communicate internally with each other and with external callers. Once a call enters a PBX, it is transmitted across an analog copper phone line or an integrated services digital network (ISDN) line to reach its intended recipient.

What is PRI trunking?

PRI is a telecommunications standard that uses physical copper phone lines to create a digital connection between your business site and the public switched telephone network (PSTN). One PRI can support up to 23 voice channels plus one channel that supports various call functionality and provides call data such as a caller's name and phone number. This enables voice, data and video traffic to be transmitted on the same line in increments of 1.54Mbps, providing speed, reliability and enhanced security for business phone systems.

A PRI circuit can be more efficient, and less expensive, than a traditional business phone service because it can be split into several channels instead of using separate analog trunks. Instead of receiving a busy signal with a traditional business phone service, PRI would enable a caller to be directed to voicemail if the line was busy.

What is SIP trunking?

SIP trunking anchors modern VoIP phone systems and supports the transmission of both voice and multimedia communications, including traditional phone calls and video conferencing. Unlike analog phone lines, SIP-based phone systems are virtualized and use an internet connection and an IP-enabled PBX to transmit communications data.

Compared to PRI, SIP enables businesses to scale up or down their telecommunications resources on demand, allowing them to be more cost-efficient and better manage their call capacity. SIP is often the best approach if your business wants to modernize its call infrastructure while remaining more flexible and agile as your business needs change.

Understanding the benefits of PRI vs. SIP

One benefit of PRI trunking is that it helps businesses simplify their communications infrastructure. One PRI connection can handle local and long-distance calls simultaneously because it can transmit this data across different channels. PRI trunking also allows businesses that aren't yet ready or don't have the funds to upgrade their systems to connect legacy PBX systems to this line without having to rely on data bandwidth to support voice communications.

On the other hand, along with the flexibility SIP provides, it also can serve as the foundation for businesses that want to implement cloud-based unified communications solutions that facilitate collaboration across different devices, applications and platforms.

SIP is better suited for businesses that have a distributed workforce or operate in a hybrid work environment where some employees are in-office and others work remotely from home or at satellite locations. By contrast, PRI trunking relies on a circuit to create physical connections, which means that it doesn't have the same capacity to distribute telecommunications resources and data across multiple, dispersed locations. However, it offers the advantage of greater security because data is transmitted over a private telephone network rather than an internet connection. Call quality may also be better because of these physical connections.

Migrating your telecommunications infrastructure

Choosing PRI vs. SIP will depend on your business needs and the level of investment your company is able or willing to make to modernize its call infrastructure.

If you're a fast-growing business, it may be time to upgrade your infrastructure and expand your call capacity with SIP trunking. If most or a growing segment of your workforce is remote, SIP also may be the best option to facilitate greater collaboration, productivity and efficiency within your organization.

While SIP is secure, internet connections come with inherent security vulnerabilities compared to private connections, which makes strong password security, 24/7 threat intelligence through a managed service provider and a zero-trust approach even more critical with SIP-based phone systems. If your chief concerns are reliability, call quality and security, relying on PRI trunking and connecting legacy PBX systems to a dedicated line with multiple channels may be the best approach for your business.

To migrate to a SIP-based system, you'll need a SIP proxy that connects to your existing PBX and a SIP-enabled phone or gateway. You'll also need to migrate your current PSTN connection to a SIP-based connection. This process entails both time and money, even if you work with an external provider. Weigh all these factors as your company decides whether to move to a SIP-enabled VoIP system or leverage a PRI connection to upgrade its telecommunications infrastructure.

Discover how Verizon VoIP and SIP trunking solutions can help you manage costs and boost efficiency.