Pros and Cons of PRI and SIP

These days, businesses have the choice between traditional land-line based telephone service (PRI) or internet based service, such as SIP trunking. There’s no single option that is right for every business, so it makes sense to carefully consider the pros and cons of each in the context of your specific needs.

PRI (Primary Rate Interface)

A PRI is essentially a T1 connection designed specifically for telephone calls. It is comprised of 23 voice channels that support up to 23 concurrent inbound or outbound calls and one data channel. The data channel takes care of caller ID and other carrier functions. The line itself is a physical copper line connected to the building.

Pros: PRI lines are dedicated physical lines that don’t rely on the customer’s internet connection. While most businesses enjoy affordable access to high-speed internet, those in areas without bandwidth sufficient to support calls over the internet can elect to go with PRI lines.

Cons: Businesses that do have access to good internet bandwidth are turning away from PRI lines for two main reasons. Cost and scalability. PRI lines (and the contracts that go with them) are provided by telco carriers. They usually have an associated per minute cost for long distance. Because they are sold only in chunks of 23 lines, many customers are paying for more capacity than they need. When businesses grow, additional PRI lines must be ordered and installed, making it difficult to quickly adjust to changing business conditions.

SIP (Session Initiation Protocol)

SIP trunking is a way of delivering voice and other unified communications features over the internet. Together with a IP-enabled PBX system, SIP eliminates the need for PRI lines. SIP trunking can be paired with an on-premises PBX or a cloud-based solution.

Pros: SIP services are usually significantly less expensive than PRI lines, saving some customers up to 60% of their communications costs. Many SIP trunking services let customers subscribe to channels in increments of one, making it possible for them to purchase and pay for only exactly what they need. What’s more, SIP channels can be added on-demand without the need for additional equipment. Customers can add (or subtract) channels so that their subscription always matches their current needs.

Cons: As we mentioned, most businesses today have access to internet connections that will work perfectly well with SIP trunking, but some do not and will need to stick with PRI. SIP trunking does require an IP-enabled PBX system, but it is possible to use an older PBX or key system with SIP. It simply requires an inexpensive device known as an analog telephone adapter (ATA). We wouldn’t call this a “con” per se, but it is important for customers to know that there are a large number of SIP service providers out there. Reliability, pricing, subscription options and customer service vary greatly, so it is important to be careful when choosing a SIP trunking partner.

The number of businesses using SIP trunks continues to grow, while the number staying with PRI is shrinking fast. This trend will continue as more and more businesses have access to high-speed internet and decision makers become more comfortable with the cloud approach. PRI lines are still an important part of the communications network and they are the best choice for some businesses, but the advantages of SIP trunking are compelling for many.