The Beginners Guide to SIP Trunking and How It Works

Jan 23, 2024 | Cloud PBX

Communication has come a long way from handwritten letters and rotary dial phones. Today, companies and individuals alike rely on sophisticated systems to connect with one another. Systems that rely on SIP trunking

But some of you who are new to the industry might wonder: What exactly is SIP trunking? And why should you care? We’re here to answer those questions in this handy guide to SIP trunking.  

What is SIP Trunking?   

What would a guide to SIP trunking be if we didn’t answer this question first? But, to answer it well, we need to cut the term in half and talk about SIP and trunk separately. 

First, what is SIP?   

Session Initiation Protocol, or SIP, is a set of rules governing how different devices communicate. Think of it as the language spoken between devices (phones, computers, etc.) that allows them to start, manage, and end communication sessions with one another. These sessions can include voice calls, video conferences, and more.  

QUICK FACT: SIP and VoIP are not the same thing. VoIP (Voice Over Internet Protocol) is a general catch-all term for communicating over the internet. SIP is a specific set of rules (i.e., a protocol) that controls how these internet-based conversations are managed. 

Next, What is a “Trunk?”   

Back in the olden days of telecom, a trunk line was a physical line or set of lines, often copper cables, connecting central offices of a telephone exchange. It could handle numerous inbound and outbound calls at once. It was an excellent way for businesses to save money because they didn’t have to purchase a dedicated phone line for each number. One trunk line could handle most, if not all, of their calls. 

With the advent of internet-based communication, trunk lines have evolved to include the SIP trunks used by VoIP phone systems.   

So – What are SIP Trunks?   

SIP trunks are virtual phone lines that use SIP protocols to connect your phone system to the internet. They allow you to use a single line for both voice and video communication. 

Graphic about what SIP Trunking is and its characteristics

How Does SIP Trunking Work?    

It uses the SIP protocol to establish and manage communication sessions, including voice calls, video calls, and other multimedia services. We’ll show you how step by step, using a phone call as an example:

  • When you make a call from your SIP phone, it sends a request to your SIP server asking if it can make a call.  
  • The SIP server checks if your call is legitimate and your phone is properly registered, ensuring everything is in order before letting the call go through. After all, nobody wants to send a fraudulent call through the system.   
  • If the call is to someone within your office or network, the server routes it accordingly. No SIP trunk is needed. If the call is going outside your network, the SIP server sends the call through a SIP trunk.  
  • Before this happens, your SIP phone (or device) uses a codec (Coder-Decoder) to compress the analog signal of your voice into data packets that can travel through the internet or phone lines.  
  • The SIP trunk talks to the destination network, figuring out the best way to connect the call and how it should sound to the person you’re calling.   
  • Once an agreement is reached, the call is sent to your recipient’s SIP server, which proceeds to authenticate the device you’re trying to reach.  
  • If everything’s in order and the device is ready to receive a call, the SIP server will make it ring.  
  • When the call is answered, the recipient’s device will decode or unpack the data packets with a codec.  
  • Now they can hear you, and the conversation can begin!   
  • While you’re talking, the SIP trunk handles the behind-the-scenes work, ensuring your conversation is clear and not interrupted.  
  • When you hang up, the SIP trunk signals to both your system and the other person’s system that the call is over.  

QUICK FACT: A SIP trunk and a SIP server are two different things! While an SIP server plays a crucial role in the overall SIP communication process, it is not what links your internal phone system to the external network. That’s what a SIP trunk does. Instead, a SIP server oversees the control and signaling aspects of the communication flow. Think of a SIP trunk as a lane on a busy road and a SIP server as a police officer directing traffic.  

Why Choose SIP Trunking for Your Business?   

Now for the big question you’ve probably had since this guide to SIP trunking started: why should you consider a SIP trunking solution for your company?  

  • Cost Efficiency: Traditional phone lines can be pricey. With SIP trunking, we switch to making calls over the internet, cutting down on long-distance charges and saving you money. Plus, you only pay for the trunks you use, avoiding unnecessary expenses. One report found that you can reduce your total cost of ownership by 60 percent if you switch to SIP trunking services 
  • Reliable Communication: SIP trunking makes your communication more resilient. Suppose there’s an issue with your power or server. In that case, calls can automatically switch to backup routes, ensuring your communication stays up and running, even during unexpected disruptions.  
  • Better Resource Utilization: Traditional phone systems often lead to underused resources. With SIP trunking, we bring together voice and data traffic, making better use of your network and reducing downtime.  
  • Quick Setup: Installing SIP trunking will be a breeze when you pick a provider like AdamsComm. It won’t disrupt your operations, and you’ll be up and running with improved communication in no time.  

Say “SIP, SIP, Hooray!” With AdamsComm   

We hope you learned something new and feel more informed about SIP trunk services from this SIP trunking guide. Understanding the fundamentals of SIP trunking, what it is, how it works, and its benefits is crucial for any company looking to stay competitive in our ever-evolving digital world. 

AdamsComm is right here to help you! We’ve got the SIP trunking solutions you need and the support you’ll love in one convenient location. Want to get started? Get in touch with us today! 

Darryl Panzer