Technology has given businesses a wide range of options for customer communication. And today, most businesses are looking for cost-effective and scalable communication solutions.
Voice is an essential customer engagement channel and SIP trunking has emerged as a powerful alternative to traditional phone lines, offering businesses increased flexibility, cost savings, and improved call quality.
In this blog, we’ll explore SIP trunking, how it works, its key benefits, business use cases, and best practices for optimal implementation.
What is SIP trunking?
Session Initiation Protocol (SIP) trunking is a digital communication technology that allows businesses to make and receive phone calls and other multimedia communications over the Internet. The term trunk in SIP trunking refers to virtual phone lines that you can use to make phone calls over the internet to anyone with a phone number.
SIP trunking vs. Traditional phone systems
SIP Trunking
- Costs: Lower costs (internet-based)
- Scalability: Easily scalable
- Reliability: Failover & disaster recovery
- Features: Video, messaging, call routing, analytics
Traditional phones
- Costs: Expensive phone lines and maintenance
- Scalability: Limited by hardware constraints
- Reliability: Prone to service disruptions
- Features: Limited to voice calls
How does SIP trunking work?
In the past, businesses relied on ISDN circuits or copper phone lines. SIP trunking replaces these with a digital alternative, transmitting voice data over the internet instead of physical wires. It works by breaking calls into digital packets and sending them across a data network.
Here’s a quick breakdown of the key components:
SIP trunk
A SIP trunk is a virtual phone line that connects a company’s phone system to an Internet Telephony Service Provider (ITSP). It enables communication between a Private Branch Exchange (PBX) and other networks, such as the Public Switched Telephone Network (PSTN), another PBX, or WebRTC devices.
DID (Direct Inward Dialing)
DID allows businesses to assign direct phone numbers that bypass a main reception line, routing calls straight to specific extensions or teams. It works with local, toll-free, and premium-rate numbers, making it easier for customers to reach the right person.
Codec
Codecs convert voice signals into digital data for transmission over the internet and back into audio at the receiving end. The most common codecs for SIP trunking are:
- G.711: No compression, offering high-quality audio.
- G.729: Compressed audio, using less bandwidth but sacrificing some quality.
Bandwidth & Call Quality
Since SIP calls rely on your internet connection, bandwidth affects call clarity. To prevent issues, routers can use Quality of Service (QoS) settings to prioritize voice calls over other internet activity, ensuring smooth communication even during high data usage.
Benefits of using SIP trunking?
SIP trunking is a great solution for businesses that need multiple phone lines, whether you’re a small business, a growing company, or a large enterprise with multiple locations. If your call volume is high or expected to increase, SIP trunking offers several advantages.
Cost savings
Traditional phone lines can be expensive, especially when factoring in hardware, maintenance, and unused lines. International calls can also add significant costs. SIP trunking, on the other hand, is typically charged per channel based on the number of concurrent calls your business needs. Pricing models.
Typical SIP trunking costs may include:
- A one-time setup fee
- A monthly broadband rental charge
- A per-channel fee that may include call allowances
- Additional call charges based on usage
Depending on your call patterns, such as the ratio of domestic to international calls, you may opt for a metered or unmetered plan that best suits your needs.
Scalability
Larger businesses may opt for dedicated data circuits for SIP trunking, ensuring higher reliability. These setups may include service level agreements (SLAs) that guarantee minimum uptime or quality of service (QoS) agreements that prioritize voice traffic over other data.
With SIP trunking, businesses maintain control over their phone system as they expand, without waiting on a provider to install new infrastructure. Whether adding new offices domestically or internationally, SIP allows you to scale up seamlessly.
Reliability
Compared to traditional phone lines, SIP trunks provide enhanced reliability. Call failover features ensure that if a primary number is unreachable, calls can be automatically redirected to a secondary number or even a different location.
For even greater reliability, businesses can implement multiple internet connections with diverse routing. This setup ensures continued connectivity even if one broadband line experiences an issue.
Real-time analytics and insights
Since SIP trunking operates via the cloud, businesses gain real-time access to analytics and call data. This allows companies to track usage, monitor availability, and optimize performance. Call logs provide valuable insights into agents’ productivity, customer interactions, and business operations.
Additionally, integrating SIP data with AI and machine learning tools can help improve customer service, sales strategies, and marketing efforts.
Centralized communication
SIP trunking consolidates communication channels by integrating voice calls, video conferencing, and messaging into a single platform. This eliminates the need for multiple, disconnected systems, making communication more efficient and cost-effective.
Once set up, SIP trunking is easy to manage, allowing businesses to oversee all digital communication from one central interface.
Call quality
SIP trunks are designed to deliver high-quality calls with ample bandwidth. As long as your internal phone system (PBX) is properly managed, you can expect clear, uninterrupted calls—even during peak usage times.
Advances in artificial intelligence now enhance call quality by minimizing issues like echoes and static, ensuring smooth conversations without dropouts or distortions.
Security
SIP trunking offers built-in security measures to protect business communications. Unlike traditional phone lines, SIP trunks are dedicated connections that providers actively monitor for any unusual activity.
Suspicious patterns can be flagged and addressed in real-time, enhancing overall security. It’s always a good idea to check with your provider about their specific security protocols to ensure your system is protected against fraud or breaches.
Flexibility
Unlike traditional phone systems tied to physical locations, SIP trunks are location-independent. Businesses can have local phone numbers in any region, regardless of their actual office location. If you relocate, you can keep the same numbers, avoiding disruptions and maintaining brand consistency.
This flexibility makes SIP trunking an ideal choice for businesses with remote teams or those looking to expand into new markets.
By switching to SIP trunking, businesses can reduce costs, improve scalability, and enhance the reliability of their communication systems—all while gaining more control and flexibility over their phone infrastructure.
SIP trunking best practices
These are some best practices and things to keep in mind when considering setting up SIP trunks for your organization:
Quality of Service
Audio is crucial to call quality and any disruptions can negatively impact communication. With all your data traffic competing for limited bandwidth, you need a way to prioritize specific traffic types.
Thankfully, QoS settings on your router let you prioritize SIP traffic for audio call quality over less demanding data traffic types.
Redundancy 
If your network goes down, it could disrupt your business operations. However, with SIP trunking, you can avoid this problem since it allows calls to be seamlessly rerouted in case of a network failure.
This means that even if one line fails, your calls can still be routed through another line. It’s like having multiple hard-wired lines for a traditional phone system.
Make sure your SIP provider takes advantage of this feature to ensure uninterrupted communication for your business.
Scalability 
The flexibility of SIP trunking helps businesses quickly scale up or down as needed. As your operation grows, you can add more numbers to accommodate your expanding workforce.
In addition, SIP trunking allows you to retain numbers irrespective of your geographical location. This means you can quickly scale globally, expanding your operations into new countries, while keeping your existing numbers.
SIP trunking use cases
Businesses have been using SIP calls for years because they help them save money while offering additional benefits like reliability, scalability, and customization.
Let’s look at some business use cases across industries:
Managing high call volumes
With Branded Caller ID, you can decrease the number of no-shows and boost the chance of contacting your customers before their appointments.
Call routing
Telcos leverage SIP to improve contact center call routing, manage account billing, and enhance agent productivity and customer interactions.
Telemedicine
Healthcare providers use SIP for telemedicine, appointment reminders, and seamless communication among staff.
Secure communication
Banks and financial institutions rely on SIP trunking for secure client communication and reducing operational costs.
Remote work
Large enterprises benefit from SIP trunking for unified communications, remote work support, and international calling.
How to set up SIP trunking?
If you’ve decided that SIP trunking is right for your business, here are the key things to consider:
1. Coverage
While global coverage may not matter today, it can be integral for your business’s success as you scale up. It’s best to find a provider that can facilitate global outbound calls and also provide various numbers across the globe for inbound calls, as and when required.
2. Choose the right provider
Look for a provider with their own network for better call quality, faster recovery times, and more reliable service. Ensure they offer local and international coverage along with 24/7 network monitoring to minimize downtime. You can also check if they have automatic failover systems in place to keep calls running smoothly during outages.
3. Manage Your Phone Numbers
If you’re switching providers, you should be able to transfer your existing phone numbers without issues. A good SIP trunking solution will also let you manage new numbers and connections from a single, centralized platform.
4. Analyze call metrics
Before committing to a provider, find out what data they offer on call performance. Many providers track metrics like call completion rates and voice quality, which can help you monitor and optimize your communications.
5. Ensure service compatibility
Not all SIP providers offer the same level of flexibility. Check whether you can customize the service to match your needs, including support for video conferencing, instant messaging, and other essential communication features.
6. Prioritize security
To protect your system, configure firewalls to allow voice traffic while blocking unauthorized access. Use encryption protocols like TLS and SRTP to secure calls against eavesdropping. Firewall setup can be complex, so working with an IT or network security expert may be helpful.
Common SIP trunking challenges (and how to solve them)
While SIP trunking has many benefits for businesses, there are also a few common challenges that businesses can face. Here’s what to watch for and how to address them.
Call quality issues
Because SIP trunking relies on your internet connection, factors like network congestion, latency, and jitter can affect call clarity. To prevent this, ensure your network has enough bandwidth for peak traffic and prioritize voice and video over other data. Regular monitoring and troubleshooting can also help maintain high-quality calls.
Security risks
Since SIP trunks connect to the internet, they can be vulnerable to cyber threats like hacking, fraud, and eavesdropping. Protect your system by using encryption, strong authentication, firewalls, and security monitoring tools. Also, ensure compliance with industry regulations such as GDPR or HIPAA.
Compatibility challenges
Not all phone systems natively support SIP trunking, and providers may differ in features and protocols. Before switching, confirm that your system is compatible or be prepared to update hardware, software, or network settings. Also, check that codecs, firewalls, and routers won’t interfere with call quality or security.
Configuration errors
SIP trunking integrates with various communication tools, such as video conferencing, messaging, and analytics. However, misconfigurations can cause issues. Using APIs, gateways, or adapters can help ensure smooth integration with your existing systems and applications.
SIP Trunking vs. VoIP: What is the difference?
SIP and VoIP are closely related but not identical. As mentioned earlier, SIP Trunking is a protocol used to enable VoIP calls by connecting a Private Branch Exchange (PBX) system to the internet. Instead of using traditional phone lines, SIP trunks act as virtual phone lines, allowing businesses to make and receive calls
VoIP, or Voice over Internet Protocol, is a technology that allows voice calls to be transmitted over the Internet instead of traditional phone lines. It converts analog voice signals into digital data packets that travel over an IP network.
VoIP enables businesses and individuals to make calls from computers, VoIP phones, and mobile devices without relying on the Public Switched Telephone Network (PSTN).
- Popular VoIP services include cloud-based phone systems like Microsoft Teams, Zoom Phone, and Skype
So the difference comes down to technology vs. protocol. VoIP is the overarching technology that enables voice communication over the internet, whereas SIP is a specific protocol used to facilitate VoIP and other communication services.
How Infobip can help you with your SIP trunking?
Infobip makes SIP trunking simple and efficient for businesses looking to improve their communication systems. With our global coverage, we provide flexible, scalable solutions to meet your needs, whether you’re expanding locally or internationally.
Our Voice solution ensures reliability with built-in redundancy, so you never have to worry about call disruptions.
Security is a top priority, and our encryption protocols ensure your communications are protected. Whether you’re a startup, a growing business, or an established enterprise, our cost-effective solutions offer flexibility and ease of integration with your existing systems.
You will have access to a reliable, secure, and scalable SIP trunking solution, helping your business stay connected, no matter where you are.