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UCaaS & Voice
PRI vs. SIP Trunk – Out with the Old, in with the New


4 min


When investigating voice options for your business you will come across two methods of voice communication, PRI or Primary Rate Interface or SIP Trunks or Session Initiation Protocol. PRIs are a traditional method that uses landlines that connect to the PSTN (Public Switch Telephone Network). Whereas SIP trunks connect calls over Internet Protocol. While both are still used today PRIs are being phased out as new, more modern approaches to technology are becoming more prominent in today’s world. In this blog, we will discuss the advantages and disadvantages of both SIP trunks and PRIs.

Understanding PRIs

PRIs, operating on T1 and E1 lines connecting to the PSTN, consist of 23 channels in a T1 and 30 channels in an E1 line. One channel is used for signaling, and the others handle voice and data. While PRIs provide a robust, reliable connection due to their physical nature, scalability becomes challenging as infrastructure changes are needed for additional channels.

Advantages to PRIs

  • Reliability and Dependency: PRIs, being physical lines with guaranteed bandwidth, offer a reliable source for voice transmission.
  • Security: Dedicated physical lines of PRIs enhance security, isolating them from external networks and reducing susceptibility to cyber threats.
  • Quality of Service: PRIs ensure crystal-clear communication with minimal latency and consistency.
  • Service Level Agreements (SLAs): PRIs provide strong SLAs, guaranteeing uptime, support, and optimal performance.

Disadvantages to PRIs

  • Cost: Installation and monthly maintenance costs are higher compared to cloud-based solutions, including hardware, PRI gateways, and setup fees.
  • Scalability: Limited scalability due to a fixed number of channels can be problematic for larger organizations with high voice traffic.
  • Dependency on Physical Lines: PRIs rely on copper lines or T1 and E1, making them susceptible to outages and system issues from weather or infrastructure maintenance.

 SIP Trunks

In comparison to PRIs, Session Initiation Protocol aka SIP trunks eliminate traditional phone lines and use internet protocol to achieve communication. Companies can easily exchange voice, video, and data utilizing internet bandwidth which makes a more cost-effective and scalable solution for their business.

Advantages to using SIP Trunks:

  • Flexibility and Scalability: SIP trunks allow businesses to add and remove lines easily as they are not tied to any physical infrastructure, so businesses can quickly make any changes to their communication requirements. Larger organizations can easily scale to make these changes quickly and inexpensively.
  • Cost Savings: Since SIP trunks use existing IP networks for voice transmissions this ultimately reduces the cost of dealing with physical infrastructure costs for maintaining physical phone lines. Upgrading to modern technology can help organizations save money on their monthly phone bills.
  • Advanced Functionality: SIP Trunks support mobility, unified messaging, and video conferencing tools.
  • Disaster Recovery: In the event of network failures, SIP Trunks can minimize downtime by routing calls over other paths and failover systems.
  • Seamless Integration: In today’s world many businesses rely heavily on UC platforms and other cloud-based technology or communication. SIP trunks allow for seamless integration into many cloud-based applications.

Disadvantages to using SIP Trunks

  • Dependency on reliable Internet connection: Since SIP trunks rely on an internet connection to transmit voice, if you have an unreliable internet source you can experience downtown and poor voice quality. Businesses need to make sure they have a reliable connection to support voice over IP.
  • Service Quality: SIP trunks are susceptible to network latency and congestion issues because there in no dedicated bandwidth like PRIs. Without appropriate network optimization businesses can experience bad call quality or dropped calls.
  • Security Risk: Since SIP trunks are using IP to deliver voice this open to cyber security threats and attacks.
  • Geographic limitations: SIP trunk availability may be limited to specific areas that are more remote and underserved. This can cause challenges in bringing in SIP trunks and may result in higher costs.

PRI and SIP trunks are two drastically different approaches in voice communication, each with advantages and disadvantages. However, SIP trunking is a more prominent way of transmitting voice as it provides an easier integrated solution that can save companies up to 50% on their phone bills. Also, copper lines are becoming obsolete, and businesses will be forced to change to SIP Trunks soon as the upkeep and cost becomes more expensive every day.

ComTec is an expert in helping customers migrate from the traditional PRIs to a more modern, cost savings connection over SIP trunks. We specialize in moving companies from traditional telecom into a modern voice connection that is reliable, inexpensive, and scalable.

Interested in learning more about ComTec’s SIP Trunks? Call (856) 691-5111 or email for more information.