SIP Line vs. SIP Trunks: What You Need to Know 

SIP trunks vs SIP lines

We have many ways to communicate with customers and prospects, but phone calls are still a tried-and-true method. Are you looking to bring your phone system into the 21st century, but don’t really want to overhaul the entire thing? Have you heard of SIP trunks or SIP lines? They might be the way to go. They enable your phone to make outgoing and take incoming calls over an Internet connection using Session Initiation Protocol (SIP) and private branch exchange (PBX). You’ll no longer rely on traditional copper lines that are quickly becoming obsolete. 

No matter if you’re looking to switch to a SIP phone system or just need some information on the terms, we have you covered. 

What is SIP Trunking? 

A SIP trunk is a communication technology that connects a company’s traditional phone system to the Internet. If you’re using a PBX to route calls, you’re still using the plain old telephone system (POTS). It’s the digital form of the traditional phone line. 

When you think of a SIP trunk, think of the trunk of a tree. It can have several branches and each of those branches can be thought of as a SIP phone line or extension. SIP lines can share one trunk, so if you have five employees who need a phone extension, you may just need one SIP trunk to support those five lines. The SIP trunk isn’t limited to desk phones, as you can use it to connect your mobile devices, or softphone to the internet. 

It’s important to note that each SIP line takes up Internet bandwidth. 

What is a SIP Line? 

A SIP line is the branch from the SIP trunk (aka session). Refer to our tree example. Each SIP line is a branch off a trunk, exchanging data from the end of the line (ie the endpoint) to the trunk and back again. In a session, a SIP line is a unit that enables an incoming or outgoing phone call, exchanging data between two endpoints. It’s a 1:1 relationship. 

You can connect hundreds of SIP lines to one trunk, so it’s incredibly useful in a call center. Each call uses a channel, but really, it’s rare that a business needs more than one SIP trunk for their needs. To figure out the number of lines you require, it’s important to know how many concurrent calls you average in a given day. 

A SIP provider typically has two types of trunk/SIP line plans: 

  • Unlimited SIP lines 
  • Unlimited with a fixed number of lines 

Benefits of SIP Trunking 

It’s not a matter of if, but when will landline phones become obsolete. You need to prepare now because you don’t want to lose customers to outdated technology. It’s essential to make the right decision on a communication system. SIP trunking will keep your business running in this digital age, and provide you with the following benefits: 

Simple Installation 

It’s not necessary to have a physical phone line or hardware to install a SIP trunk. Just a reliable, high-bandwidth Internet connection. 

Cost savings 

SIP trunks can lower your current phone expenses. Because you’re using the Internet, your domestic calls are free. International calls can be significantly cheaper than using a traditional phone line, as well. 


If your traditional phone system goes down, there are no redundancies. If there’s an outage, you’re without your phone system. But with SIP trunking, you’re still up thanks to built-in redundancies! Even if you lose your internet, you can have your calls forwarded to a secondary phone quickly and easily. 

Advanced Features 

By enabling SIP trunking, you open your business up to utilize additional features a traditional phone is unable to offer. On top of voice, you can use text messaging, screen sharing, and video conferencing in your package. You’re also allowing your employees to work from anywhere, instead of being tied to their office phones. 

Advanced Communications for SIP Trunking 

Get ready for a brand-new phone system with Advanced Communications. If you’re not ready to make the move to the cloud, SIP trunking might be best for your business’s needs. The experts at Advanced will get to know your business and fit you with a system that best meets your goals. Contact us today and let’s get the conversation started on how we can begin to future-proof your communications technology.

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