SIP Trunking VS. PRI: What’s The Difference?

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The truth about deciding whether to use SIP or PRI is not as simple. Although more businesses are abandoning PRI, both options still have advantages and disadvantages. Let’s take a look at SIP trunking and PRI. There are some situations where both solutions work well.

What is SIP?

The endless debate about SIP vs. PRI is an apples-to-oranges comparison. Both offer the same result for businesses — a connection between the business’s internal telephone systems and the larger PSTN. However, their methods to achieve this goal are different enough to merit discussion.


SIP trunking is a virtualized version of business telephony. SIP trunking works over a data connection. Companies can send their calls and multimedia messages via an internet connection. Gateways and other specialized hardware are available to companies that want to get rid of a standard PBX. Instead, a company might upgrade its infrastructure and use newer, more advanced softphones.

This is particularly important considering the most significant SIP benefit: multimedia communication. SIP trunking is the best way to get companies’ unified communications and collaboration tools. It’s easy and scalable, and it can be used by businesses who want digital voice and video conferencing, and other high-tech devices. In addition, SIP trunking is likely already in use by your company if you make heavy use of services like desktop sharing.

SIP trunking’s virtualized nature makes it more scalable than PRI’s restrictive architecture. PRI’s maximum number of active calls can be “hardwired,” so the carriers’ number and bandwidth limit a SIP trunk’s capacity.

SIP trunking is a good choice for international call-dependent companies. SIP trunking is far less expensive than PRI for outbound international calls. This is similar to how voice over internet protocol (VoIP) dramatically reduced the cost of international calls over regular landline calls. SIP trunking is generally cheaper than PRI, particularly with multiple PRI connections.


SIP trunking is dependent on a data connection. Therefore, businesses must ensure that they have enough capacity to support all their VoIP phones and equipment. In addition, companies may require additional bandwidth if they receive many simultaneous calls. SIP trunking can be cost-effective over the long term, but some companies might find the initial setup fees prohibitive.

Advantages of PRI

PRI’s greatest strength is its connectivity. However, if quality and call uptime are essential to you, such as a situation where even one dropped call or hiccup can lead to a disaster in the office, PRI’s stability and ability to offer consumer-friendly service levels agreements (SLAs) may mean you have less to worry. This is worth looking into in healthcare, where call quality is a significant concern.

Disadvantages of PRI

Some people think PRI is outdated. However, most U.S.-based customers deploy PRI over a dedicated T1 line. Similar principles apply in Europe, where PRI can often be deployed over an E1 connection. Although T1 and E1 still have benefits over standard internet connectivity in business settings, it’s clear that they’ve been lost in the age of public internet, which offers better speeds and lower prices. This could immediately raise questions about the longevity and value of PRI in certain IT circles.

PRI primarily uses these connectivity types. This is the biggest drawback of the solution. Each connection offers a limited number of voice channels (24 for T1 and 30 for E1) but only allows for a certain number of simultaneous calls. If you use PRI in the U.S., and you need to make 35 concurrent calls, you will require two physical connections. 13 channels will remain unused unless you have an unusual circumstance where you require more active calls than the maximum.

Active calls are different from active phone numbers. For example, a company that uses PRI with direct dialing may have hundreds of phone numbers but only support the predetermined number of active calls.

Head-to-Head Comparative Study (SIP vs. PRI)

It may help to compare the main differences between SIP and PRI when trying to make a call.


SIP is generally more cost-effective than PRI, especially on a large scale. Although SIP has some setup fees, it offers attractive benefits when it comes to long-distance calling as well as special features.

Flexibility and Scalability

SIP is much more flexible and scalable than its PRI counterpart. A company must order 21 additional lines for expansion of its PRI capacity. This is regardless of whether the 21 lines are needed. It can be time-consuming and disruptive for businesses to order a new PRI circuit. On the other hand, SIP trunking allows companies to scale up and down their service as they need them without making a sizeable ongoing investment.

Digital Transformation

SIP trunking allows companies to slowly transition away from legacy communications technology or completely modernize their business. SIP trunking allows businesses to access VoIP, unified communication, and other innovative technologies that enable true digital transformation. A PRI circuit is not the same.

Business Continuity

SIP is appealing from a business continuity standpoint. It allows you to preprogram redundancies in services in a disruption or emergency. In addition, SIP trunking can be used to reroute calls between locations, which helps your company keep in touch with customers and business partners even in the face of a disaster or technical malfunction. Pris does not offer this level of availability and redundancy.

Which is best for you?

The debate over SIP trunks or PRI depends on your business’s communication needs and geographic location. For example, PRI may be more beneficial for smaller organizations located in rural areas with insufficient internet access to support SIP trunking. On the other hand, SIP trunking may be better for larger businesses in areas with better connectivity. This is particularly true for large enterprises that require many active calls. They could also make use of advanced unified communication and collaboration features.

SIP trunking is more flexible, scalable, and functional than PRI. These are the factors you require from your communications system, and SIP trunking may be the best option. On the other hand, PRI might be the right option for you if technical limitations limit your location’s connectivity options.

To learn more about modernizing your business communications, contact Twiching General Trading Company.