SIP vs. PRI – What’s the Difference?

July 17, 2015

What’s the difference between SIP and PRI?

Let’s start with the definitions:

  • PRI = Primary Rate Interface:  A popular digital telephone service delivered over T1 lines
  • SIP = Session Initiation Protocol: A flexible protocol that enables use of Voice over IP (VoIP) services and one that you can easily expand and add features to.

When your boss asks you about the advantages of SIP trunking vs PRI for your office communication needs, what do you tell them?

23 Reasons Why SIP is Better than PRI

If you’re in the U.S. using a T1 line, you could simply say that there are 23 reasons why the benefits of SIP far exceed those of PRI.

After all, PRI over T1 is limited to 23 voice channel (plus one signalling channel).

One downside to PRI is that if your business grows and you add more employees you’ll need to purchase and configure another PRI regardless of whether your new call capacity requires a only a few extra lines or all 23 voice channels.

Excellent call quality is guaranteed with a PRI however, since it connect directly to public telephone networks. That quality comes at a price as you’ll have to maintain significantly more hardware such as telephony cards and PBXs plus  cabling.

SIP Fits Your Dynamic, Changing Business

With SIP all you need is a fast internet connection. And when you’re not making any phone calls, that bandwidth is freed up for your data network.

Whereas PRI uses hardware and a dedicated T1 line to make voice calls, your SIP network is virtual, uses your existing internet capabilities, and can be configured to work with almost any phone system.

What is This Going to Cost Me?

Like most applications there are a lot of variables. Roughly speaking, a PRI phone system can run you in the hundreds of dollars per month versus the twenty dollars per month for a single channel of unlimited SIP trunking service.

Expect phone cost savings up to 50% with SIP.

SIP is flexible enough to grow or shrink as your calling needs change. SIP trunks can be configured for as many, or as few, simultaneous calls as you need with a simple software change.

Pros and Cons

Here’s a quick rundown of some of the main pros and cons of SIP vs. PRI:

SIP PRI
Connectivity Virtual phone line over the internet shares bandwidth with your existing data network. Can be shared company-wide and remotely. Physical phone line that requires a physical connection. Can only be used onsite or at a single networked location.
Hardware Needed PoE switches, Session Border Controllers (SBC), SIP Gateway Telephony cards, PBX, dedicated T1 line, VoIP gateways
Cost Pay for what you need – pay per number of lines needed PRI lines are sold per circuit.
Scalability Increase your bandwidth or just ask your service provider for more virtual lines. Can be done in as little as a few hours. Upgrade 23 lines at a time with additional PRIs. Can take a couple weeks to get hardware installed and lines configured.

What’s The Best Solution for Me?

Every application is different so what works best for you may be different than what you’re even reading here.

The obvious benefits of SIP are cost, scale up or down, more features and greater control over features, and less hardware. But some businesses, for example, use a combination of both PRI and SIP – PRI is used for local calls and SIP is used to save money on international and long-distance calls.

Consider your options and figure what works best for you.

In the Event of Failure

While you’re weighing your options, here’s one last thing to keep in mind; something that most people really like about SIP.

What happens when there’s a storm and the telephone lines go down? If you’re using PRI you’ll just have to wait until they’re back up and running to make phone calls.

If you’re using SIP and you lose your internet connection, failover ports and a backup internet connection can keep you operating with only a slight disruption in service.

In today’s day and age people want choice and they don’t want to wait for anything. If you’re ready for it, SIP can offer you all of that simply, quickly, and cost effectively.