For several decades, the Public Switched Telephone Network (PSTN) consisted of only analog lines, which were physical connections between endpoints. In the 1980’s, the telephony industry began preparing for digital services, and by the turn of the century, the majority was using Primary Rate Interface (PRI) lines. PRI was a major advancement because it allowed a business to make and receive 23 simultaneous calls over the same line, as opposed to one call per line with analog.
With this setup, all office extensions connect to your company’s internal phone system (your PBX), which then connect to one or more PRIs, which lead straight to the telephone company (PSTN). The number of PRI connections a business has depends on the number of concurrent calls it needs to be able to make. Unfortunately, PRIs don’t make an efficient use of business resources since unused channels sit dormant. For example, if a business requires 27 call paths, they would need to purchase two PRIs, which leaves them with 19 unused channels.
While the PRI connections worked fine for a while, a more efficient and budget-friendly solution began to emerge: SIP trunks. SIP trunks have quickly been replacing the old way of communication by utilizing voice calls over the internet, more commonly referred to as VoIP.
SIP & SIP Trunking
Session Initiation Protocol (SIP) is the key protocol that supports VoIP calls, and does so by setting up and tearing down real-time sessions (calls) between two endpoints (phones). SIP works with a variation of devices and applications, including voice calls to softphones, video calls, audio conference sessions, and other UC applications.
A SIP trunk is a virtual connection between an IP phone system (IP-PBX) and an Internet Telephony Service Provider (ITSP- the SIP provider) and is connected over a business’s existing data network. For a company that wants to take advantage of SIP, they can eliminate the PRI connections and rely on their existing internet connection to make calls.
So which is better for business- PRI vs SIP? Let’s compare the two:
If voice quality is the highest priority for your business, you need fax to the desktop, and you have the budget; you might benefit from a true T-1 PRI more than you would from SIP trunking. However, if you have a solid internet connection, don’t need to fax to the desktop, want to save 20-60% on your monthly communications costs, and want access to advanced unified communications features; SIP trunking is most likely the optimal choice for you.