SIP Trunking (dial-tone) 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 (Qwest), AT&T, Integra, Verizon, XO, etc. are providing SIP services now. Business owners should wade through the two technologies to understand where telecom is headed.
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. 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 meansthere are more users than call channels. That’s possible because in most businesses, not everyone is on the phone at the same time.
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. With a PRI, the location dictates what area code and prefixes can be used. PRI’s don’t make an efficient use of a company’s resources. Unused channels sit dormant.
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. The call quality depends on the network it is being transmitted on. 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. Unlike PRI, additional SIP trunks can be implemented in days, not the weeks.
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 & makes better use of a company’s resources. PRI will be phased out over time.