Both SIP & PRI have their benefits and drawbacks. To find out what will work best for your business let's explore the differences…
Before we dive too deep. Let's get some definitions out of the way:
- SIP Protocol is the underlying standard beneath SIP trunks and most VoIP technologies.
- SIP Trunks are the pathway from your phone system to your SIP provider.
- SIP Providers are similar to the phone company. You pay them a monthly fee and they connect your calls using SIP trunks. Unlike traditional phone companies who use physical lines to your business the SIP trunks they provide are virtual and use your internet connection.
SIP protocol is the newest of the two technologies, having been developed in 1996, SIP saw wider adoption in the early 2000's after the protocol was standardized. Rather than the traditional method of a phone company bringing in a large wire with copper pairs known as a PRI into your business SIP trunks are "virtual cables" that use your existing network along with the internet to route your calls to a SIP provider who then connects your call to anywhere in the world.
What are the drawbacks to SIP?
One of the major drawbacks to using a SIP provider is bandwidth. When you send an email across the country via the internet it is broken down into 1's & 0's and then reassembled on the other side. If those pieces are out of order they can be reassembled and if they don't make it the technology is smart enough to send it again.
With phone conversations over the internet this simply won't work. The person on the other side of your call can't receive just parts of your sentence and reassemble it or wait for the rest to come in. Voice has to be received sequentially and without missing any parts.
With SIP, if your network is unreliable or your Internet Service Provider's (ISP) network is unreliable or down, you could lose parts of the call or simply not be able to make a call. Your call quality could also be affected by the amount of bandwidth being used. For example: without the proper internal network infrastructure , routers, cabling, etc., if someone in your business is streaming a YouTube video or downloading a large file you could experience part of the call being dropped or degraded voice quality.
Ok, Why Would I Choose SIP?
The bandwidth concerns we talked about above are important but that doesn’t mean they can't be overcome. If you have a good network in place or are willing to make the investment to ensure your network is reliable SIP can be a great choice for two main reasons:
- Cost SIP can save your business quite a bit of money. Assuming you have a strong network and internet connection already that cost of adding SIP trunks is drastically cheaper than adding a PRI.
- Scaleability One benefit of SIP is that you can typically add as few or as many concurrent call sessions as you would like. We'll cover concurrent call sessions and how this differs from PRI below.
Primary Rate Interface or PRI is the older of the two technologies. PRI's are a circuit from your phone company to your location. Unlike SIP Trunks these are physical copper lines that do not use your internet connection in any way.
Benefits of PRI
PRI's may be an older technology but that doesn't mean they don't still provide value to many businesses. One major benefit is reliability. A PRI is physical line whose sole purpose is to carry your voice communications. This technology has been around for a long time and generally just works when you expect it to. SIP relies on several components such as your network, routers, and internet connection PRI is a direct connection between your phone system and the phone company who routes your calls. By having this direct connection you are able to eliminate several points of failure and get around the biggest drawback of SIP which is your bandwidth.
What are Concurrent Call Sessions?
When you use a PRI you are typically able to have 23 concurrent call sessions per PRI line. While you can have up to 100 phone numbers per PRI you can only make 23 incoming/outgoing calls at one time. If you need to make 24 you will need to add another PRI line.
What are the drawbacks to PRI?
While PRI lines are reliable and do not need to use bandwidth they do present some drawbacks. Perhaps the biggest drawback is cost. A PRI line is typically around $500 dollars per month for 23 concurrent calls. For 23 SIP trunks the cost is closer to $350 per month. In addition to the higher monthly cost the cost of a PRI card in your phone system is often around $1500.
One other major issue is scalability. A PRI line is 23 concurrent calls sessions. Typically you need to purchase a full PRI whether or not you need all 23 concurrent call sessions. For a smaller business who may only need 4 or 5 sessions at once paying $500 dollars per month could be overkill. SIP on the other hand will allow you to purchase 1 or 2 SIP trunks at a time and scale as your business grows. With a PRI these costs continue as you grow. If you have a PRI and you find that you need to have 25 concurrent call sessions you will need to add another PRI line with a full 23 more concurrent call sessions bringing your monthly total to around $1000.
So which is better for your business SIP or PRI?
It all depends on your business needs. While PRI might often get looked at as an outdated technology, the truth is that a PRI might be perfect for your business. If you have the right infrastructure in place and a strong internet connection there are many benefits to SIP service as well.
Before making a decision we recommend that you have a professional visit your business and evaluate your network and internet connection. If possible, get a couple companies to come give you an evaluation. Often, this is free or relatively cheap visit that can save you money and headaches in the future.