Businesses have to choose between SIP trunking or PRI trunking for voice over internet protocol (VoIP). While PRI is considered to be reliable, the copper wires in the PRI trunks can be easily damaged by weather, vandalism, and aging infrastructure. SIP trunks offer greater reliability and increased resistance to weather and other types of damage.
Learn more about these two VoIP connectivity options.
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If you are still trying to choose between SIP and PRI trunking, Symplicity Communications can help! Schedule a free consultation today, and let’s discuss your company’s needs.
What Is SIP Trunking?
Session Initiation Protocol (SIP) trunking is a method of delivering voice calls over internet protocol (IP) networks rather than traditional public switch telephone network (PSTN) circuits.
With SIP trunking:
- Phone calls are transmitted as data packets over internet connections instead of dedicated phone lines. This allows calls to be consolidated with general internet traffic, which reduces costs.
- SIP is used to establish, manage, and terminate voice sessions between communication endpoints such as phones and VoIP servers.
- Users use regular office phones. But calls become internet data instead of transmitting over physical phone lines.
What Is PRI Trunking?
PRI trunking transmits voice and data calls over traditional physical circuits. With PRI trunking, the telephone company provisions dedicated, point-to-point digital circuits. These circuits connect the private phone system to the PSTN.
The main technology behind PRI trunking is called Integrated Services Digital Network (ISDN). The ISDN packages and transports calls over digital circuits instead of analog lines. PRI uses twenty-three simultaneous 64 kbps channels (B channels) and one 64 kbps signaling channel (D channel). This allows PRI to handle 23 calls per circuit.
Unlike SIP trunking, PRI trunking does not convert voice into IP data packets. Instead, calls remain as circuit transmissions over dedicated infrastructure. So PRI does not transport calls over the public internet. Telephone service providers manage the dedicated T1/E1 lines centrally for reliability and call quality control.
Key Differences Between SIP and PRI Trunking
Here are some primary differences between PRI and SIP trunking:
- Cost. SIP trunking is typically less expensive than PRI, since SIP leverages existing internet connectivity rather than dedicated phone circuits.
- Scalability. It is easier to scale SIP trunk capacity up or down as needs change. PRI has a fixed capacity per T1/E1 line purchased.
- Flexibility. SIP supports more advanced features such as video calling, instant messaging, and mobile integration.
- Reliability. PRI has traditionally been viewed as more reliable since it uses dedicated infrastructure less prone to internet congestion. But with good bandwidth, SIP reliability is also robust.
Technical Details
SIP and PRI trunking differ in their technical details, including how calls are transmitted, which codecs are used, call routing processes, and quality of service considerations.
- SIP trunking uses VoIP to transmit call audio over IP data packets rather than dedicated circuits.
- PRI trunking relies on time-division multiplexing to transmit calls over dedicated digital lines such as T1 and E1. Calls do not traverse IP networks.
- SIP supports more flexible audio codecs such as G.711, G.729, and Opus to encode and decode calls.
- PRI is typically limited to G.711 codecs due to reliance on older infrastructure.
- SIP call routing involves IP-based SIP proxy servers to handle setup over dynamic IP networks.
- PRI uses SS7 signaling to route calls over static telephone infrastructure.
- SIP call quality depends on having robust internet bandwidth and QoS controls.
- PRI call quality is less impacted by network traffic but has a fixed capacity per T1 or E1 circuit.
Implementation Factors
Businesses must weigh several key considerations about integration and operations when they choose between SIP and PRI trunking, including:
- On-premises vs. cloud-based options: SIP and PRI trunking each support on-premises equipment installed locally or cloud-based solutions hosted remotely by a service provider.
- Integration with phone systems: both trunking options need to interconnect with the existing corporate phone system. SIP may support more advanced features but requires compatibility factors.
- Security considerations: PRI relies more on dedicated, secured provider lines while SIP traverses the public internet, requiring businesses to establish security layers.
- Disaster recovery and backup plans: to ensure uninterrupted communication, redundancy and backups of primary SIP or PRI trunks are critical through methods such as duplicate equipment.
Pros and Cons
SIP and PRI both facilitate voice communications but use different methods with unique advantages and disadvantages.
The benefits of SIP trunking include:
- Lower ongoing costs as it utilizes existing data connectivity
- Scalability to easily adjust capacity as needs change
- Flexible feature set—supports advanced call options
The potential downsides of SIP include:
- Call quality reliant on internet reliability
- Data security protections required against cyber threats
The benefits of PRI trunking include:
- Dedicated infrastructure for consistent call clarity
- Unimpacted by other corporate bandwidth usage
- Tried-and-tested legacy reliability
The potential downsides with PRI include:
- Upfront investment and monthly access costs
- Cannot dynamically scale the number of lines supported
- Limited feature expansion flexibility
Organizations should consider their budget, call volume, reliability needs, and functionality priorities to make the right choice.
When does PRI Work Best?
PRI trunking can work very well for organizations that need reliable voice connectivity but don’t require lots of advanced features or frequent changes.
Specifically, PRI makes the most sense for:
- Companies with steady calling volumes that can justify fixed PRI circuit costs
- Businesses reliant on fax and analog transmissions unsupported by SIP
- Call centers handling high volumes of inbound calls
- Regulated sectors that require specialized legacy system compatibility
- Firms unwilling to migrate from complex legacy phone equipment
PRI trunking fits best for organizations with relatively simple (yet mission-critical) voice needs that leverage traditional telephony infrastructure. Dedicated connectivity provides rock-solid stability even during internet outages.
When Is SIP Preferable?
SIP trunking provides the most value for organizations that need flexibility, advanced features, frequent changes, and cost efficiency.
SIP makes the most sense for:
- Rapidly growing businesses with calling spikes or fluctuations
- Companies with mobile and remote workers that need unified communications
- Organizations that leverage cloud contact center capabilities
- Enterprises that take advantage of conferencing and virtual connection
- Startups that cannot to invest in costly physical phone infrastructure
SIP trunking fits best for organizations with dynamic calling patterns, complex implementations across multiple locations, and growing unified communication needs. However, redundancy planning is required to ensure 100% uptime on par with legacy telephony.
About Symplicity
Consider us your trusted partners when choosing between PRI and SIP trunking. We deliver comprehensive solutions that can transform the way you manage your communication infrastructure and optimize your connectivity.
Here is how we can help:
- Our top priority is helping you establish a robust and dependable trunking connection. This guarantees constant accessibility to your critical voice channels and data services.
- We are dedicated to providing you with a flexible and scalable trunking framework. As your communication needs evolve, our services evolve with you.
- We recognize the importance of efficient communication. Our solutions are thoughtfully designed to foster collaboration among your network administrators and partners, facilitating smoother communication management workflows and decision-making processes.
We provide expertise, guidance, and ongoing support for seamless SIP trunking implementation. You can trust that your SIP trunking will be efficient, reliable, and equipped with the capabilities necessary for your business to excel in the world of modern communication.
Explore our solutions page for a comprehensive overview of our capabilities
PRI vs. SIP Trunking FAQ
What is the purpose of SIP trunking?
The main purpose of SIP trunking is to deliver voice calls over IP networks instead of traditional wired phone lines. This allows companies to save money by consolidating voice and data services into shared high-speed connections.
What is the SIP to PRI converter?
A SIP to PRI converter, also known as a SIP trunk to PRI gateway, is a device that connects modern SIP trunking services to PRI-based phone systems. This allows businesses to continue using their existing phone equipment while taking advantage of the benefits of VoIP services through SIP trunking.
It’s a cost-effective solution for businesses that are not ready to invest in new phone systems but want to start using SIP trunking.
Do you need a PBX for the SPI trunk?
An SIP trunk typically connects to a private branch exchange (PBX), which is the internal phone network used within a company. The PBX manages calls between users on local lines while allowing all users to share a certain number of external phone lines. The SIP trunk allows the PBX to send and receive calls via the internet.
What ports are used for the SIP trunk?
SIP trunking utilizes existing IP data network connections and does not use dedicated telephony ports. SIP messages flow over standard transmission control protocol (TCP) or user datagram protocol (UDP) ports such as 5060 and 5061.
What are the two types of PRI?
The two main PRI types are:
- T1 PRI lines, which are common in the United States, Canada, and Japan and provide 24 channels
- E1 PRI lines, which are common in Europe and Australia and provide 30 channels
What are the different types of SIP trunks?
Different types of SIP trunks are:
- Hosted SIP Trunks are delivered by a provider with all hardware located in their cloud infrastructure rather than on business premises.
- Cloud-based SIP Trunks are virtual phone lines delivered over the public internet by a third-party SIP provider rather than self-managed trunks.
- On-premises SIP Trunks rely on businesses deploying dedicated session border controllers and SIP-capable PBXs within their private data network.
- Hybrid SIP Trunks blend third-party hosted trunk capacity with some degree of customer-controlled on-premises hardware that supports key SIP functionality.
How to migrate from PRI to SIP?
To migrate from PRI to SIP, you should:
- Assess existing infrastructure
- Procure compatible equipment (session border controllers, for example)
- Implement new SIP lines alongside legacy circuits
- Train users
- Port phone numbers
In the end, you should decommission old PRIs once the transition is complete.
What is the difference between SIP trunking and VoIP?
SIP trunking and VoIP are related but distinct concepts:
- VoIP is a broad term that refers to any phone call made over the internet, instead of traditional telephone lines.
- SIP trunking is a specific type of VoIP technology that enables the connection of a PBX to the internet. It uses the SIP protocol to manage multimedia communication sessions such as voice and video calls, video conferencing, etc.
SIP trunking is one method of implementing VoIP services.
What protocols are involved with SIP trunking?
SIP trunking relies on session initiation protocol (SIP) and voice over IP (VoIP) protocols to direct call setup, call control, multimedia sessions, and voice data transmission over IP networks.
How many simultaneous calls can a PRI line support?
A standard T1 PRI line can handle 23 concurrent calls while an E1 PRI line (used internationally) can facilitate up to 30 simultaneous telephone conversations per circuit.
Does migrating trunks require changing phone numbers?
Phone numbers can typically be ported between legacy telephone carriers and SIP-based providers when changing networks. The phone number porting process coordinates with the existing regional telephone network company and the new voice service SIP provider.
Customers then maintain existing caller IDs and continuity through technical changes required on back-end systems.
What security measures safeguard SIP trunks?
Protecting SIP’s voice packet transmission involves multiple network security products:
- Session border controllers to monitor VoIP traffic between local and external networks
- Next-generation firewalls
- Intrusion prevention systems to detect bad packets
- Encryption to make voice data unreadable
- Multifactor login authentication on mobile phones, softphones, or media gateways plugged into the corporate network to ensure secure access
