SIP spells the beginning of the end for PRI.  PRI represents the traditional Public Switched Telephone Network (PSTN) while SIP represents Voice over IP.  SIP is the future, PRI is the past. Major providers like CenturyLink, AT&T and Verizon are providing SIP services now.  Business owners should wade through the two technologies to understand where telecom is headed.

sip vs priWhat is PRI?

PRI is a digital circuit providing 23 channels or voice paths and one channel for signaling.  Signaling provides Caller ID information and other data that helps the circuit perform.  PRI is a direct connection to the PSTN, so the call quality is excellent.  It is a good substitute for POTS or business phone lines, when a business requires more than ten phone lines.  A business line cost an average of $40 a month.  A PRI can be had for around $500 a month, so as soon as you exceed 10 phone lines, you’re probably better off with a PRI.

Advantage and Disadvantage of PRI

PRI allows for the use of DID’s

DID’s are phone numbers.  A PRI with DID’s allows a business to have more phone numbers than phone lines, offering greater number flexibility.  Typically, a PRI is “oversubscribed” which means there are more users than call channels.  That’s possible because in most businesses, not everyone is on the phone at the same time.  If a business had 40 employees and wanted phone numbers for every employee, with POTS lines, they would need 40 phone lines.  At $40 a phone line, the cost would be $1600 a month, or more than three times the cost of a PRI.

Required a T1 card

To utilize a PRI, a T1 card is a required component in a business’s phone system or PBX (Private Branch Exchange).  That’s not an issue in newer systems.  In an older system, a business should expect to pay between $500 and $1200 to add a T1 card.  If the business is using POTS lines, it should be easy to calculate the ROI for the purchase of a T1 card.

Voice communication

With PRI, your voice communication is completely separate from your internet or data traffic.  A new loop, from one of the incumbent phone companies, is required for each individual voice and data circuit and a separate run of cable is necessary for a business’s voice and data networks.  A PRI can be integrated with a MPLS network, but that takes place on the customer’s premise and their location dictates what area code and prefixes can be used.

Don’t make efficient use of a company’s resources

PRI’s don’t make efficient use of a company’s resources.  Unused channel sits dormant.  Each PRI offers 23 channels, so if a business required 50 call paths, they would need to order three PRI’s, for a total of 69 channels or try to get by with two PRI’s and 46 channels.

What is SIP?

SIP trunks are call paths that can be ordered in any increment. SIP is Voice over IP, so your voice calls are transmitted across the internet, along with emails, data files, etc.  The call quality can range from not great to very good, depending on the network it is being transmitted on.  Most carriers offer QoS (Quality of Service) and CoS (Class of Service) on their MPLS networks.  MPLS is Multi-Protocol Label Switching and it’s a type of wide area network that facilitates VoIP.  QoS and CoS are standards or settings utilized to assure call quality.

Advantage and Disadvantage of SIP

Originally, SIP was sold by smaller companies that didn’t own a network or provide the customer’s internet connection.  This led to poor call quality and shoddy performance, causing some business people to be leery of VoIP, but now carriers offer unified solutions that assure call quality.

Efficient use of resources

SIP provides for a more efficient use of resources because the voice communication rides over a business’s data network.  There is only one network to manage, one set of cables required, if the SIP trunks aren’t in use, the bandwidth is freed up for data and a business isn’t required to order call paths in increments of 23.  SIP trunks can be aggregated at the company’s host location and trunks can be shared companywide, so economies of scale can be realized.


SIP allows for even more phone number flexibility and functionality.  You can incorporate traditional DID’s and out of area DID’s, so you can make any number ring at any location, nationwide.  It also allows for failover.  Should a company location or call center get knocked out by a natural disaster, the company’s phone numbers can be routed to a separate location.

Time to implement 

Unlike PRI, additional SIP trunks can be implemented in days, not weeks.

Sold in packages

Competitive Local Exchange Carriers (CLEC’s), like TW Telecom and Integra, are offering SIP much the same way as more traditional integrated T1s.  SIP trunks are sold in packages that include internet access, call paths and long-distance minutes and the service can be delivered so it will function with analog or digital phone equipment.

Last Few Talk on PRI vs SIP

PRI or SIP might seem complicated but they don’t need to be.  PRI provides voice communication over the phone network.  SIP provides voice communication over the internet.  SIP is more versatile, scalable and makes better use of a company’s resources.  PRI will be phased out over time.

If you would like to receive more information regarding SIP or consultation on moving your voice communication from PRI to SIP, call CarrierBid today or complete the form on the right side of this page.  

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