Customers of business phone service usually establish dial tone with either PRI or SIP services. Each approach has some advantages and tradeoffs, so it is important to choose the type of service that makes the most sense for your business, your location and your checkbook. Let’s examine each.
PRI (Primary Rate Interface)
PRI is essentially a “smarter” T1 connection that is made up of 23 voice channels to support 23 concurrent calls and 1 data channel. The data channel is handles caller ID and other carrier functionality. A PRI line is a copper line connected to the customers building.
Advantage: The main advantage of a PRI line is that it does not rely on the customer’s Internet connection. Customers in areas where bandwidth sufficient to support voice calling is not available should look to PRI lines for their primary voice services.
Disadvantages: There are two significant disadvantages with PRI lines. Price and scalability. PRI lines are generally provided by traditional telco carriers and are often accompanied by long term contracts for service and long distance. Because PRI lines must be purchased in increments of 23 customers frequently pay for more capacity than is needed. When companies do grow and need the ability to complete more concurrent calls, additional PRI lines must be purchased and installed.
SIP (Session Initiation Protocol)
SIP services are a method of delivering voice and other unified communications (UC) services over the Internet. They utilize a SIP enabled PBX (private branch exchange) and eliminate the need for PRI lines. SIP services can be deployed for use with a traditional on-premises PBX or a hosted solution. Gateways are used to deliver calls to the public switched telephone network.
Advantages: SIP services are generally less expensive than PRI lines. Most SIP providers sell channels one at a time, making it possible for customers to purchase only the number required for their anticipated call volume. In addition, they can be provisioned immediately without the need for more equipment, so users can scale up on-demand.
Disadvantages: Because the Internet is used to deliver calls, bandwidth is an important consideration. Access to sufficiently speedy connections is widespread these days, but not entirely ubiquitous. Customers with analog PBX systems can take advantage of SIP services, but will need to use an analog telephone adapter (ATA). Although not a disadvantage, customers should be aware that there are a large number of SIP service providers and that pricing, packaging, reliability and customer service vary greatly. It is important that customers choose a SIP services provider wisely and understand exactly what they are getting.
SIP is becoming increasingly popular as the available of high-speed Internet spreads and more of our infrastructure moves to the cloud. PRI lines continue to play a role and are the best option for some customers, but the cost advantages of SIP are compelling and it is increasingly the best choice for many businesses.