SIP Trunks: A Guide for the Bewildered

SIP Trunking might sound like geeky tech jargon - because it is - but it's also a powerful communications technology. If your business is serious about moving to IP communications, it is essential to make sense of SIP Trunking.

At MyNetFone, we believe SIP Trunking shouldn't be confusing or complicated. And we've prepared this useful guide to help you better understand SIP Trunks, and how to use them.


The basics: What is a SIP Trunk?


A SIP Trunk is the digital equivalent of a phone line. A SIP Trunk replaces a traditional phone line, and enables you to make and receive voice (or video) calls using the internet.

Organisations often use SIP Trunks as a way to connect their PBX equipment to modern IP communications networks (like MyNetFone), and thereby, to deliver calls.

What's with the geeky name?

Sometimes, geeks aren't that imaginative. SIP Trunking simply means what it is:

SIP = Session Initiation Protocol (the computer language that sends / receives calls)

Trunk = A connection between two points


Who uses SIP Trunks?

SIP Trunks are used in offices, to enable internet-based calling via a PBX (Private Automatic Branch Exchange) phone system or UC (Unified Communications) platform. The SIP Trunk technology provides a digital connection, sending calls and information between the PBX and telephone network.


Is it right for me?

SIP Trunking is just one of many ways to run an office phone system. It may not be a suitable solution for every business. Importantly, SIP Trunking requires an existing phone system and cannot be setup without a technician. With MyNetFone, both traditional (PSTN / ISDN) and modern (IP) phone systems can be connected. So you are able to keep the same phone system and handsets when you move to the NBN.


Get started with SIP Trunks 


SIP Trunking diagram - How it works



To properly understand SIP Trunking, it is useful to compare it with other communication technologies.

SIP Trunks vs VoIP


VoIP is more of a retail grade service. SIP Trunks are business-grade. SIP Trunks can also deliver multimedia (not just voice). They can be used in conjunction with video phones, and UC platforms like Microsoft Lync / Skype for Business.

SIP Trunks vs Hosted PBX systems


SIP Trunks require an existing PBX or Unified Communications platform, which will need to be setup by a technician. (If you lack the technical skill, MyNetFone can recommend a partner solutions provider). However, one advantage of SIP Trunking is lower CAPEX, because you can keep your existing handsets and PBX equipment.

Hosted PBXs are all-in-one – incoporating handsets and PBX as a complete solution. If you have existing handsets, you cannot use them with a hosted phone system. Instead you will need to purchase new preconfigured handsets. With much of the configuration done, hosted PBXs are very easy to setup and scale.


SIP Trunking vs Analogue (PSTN / ISDN) PBXs


SIP Trunks are often equated to 'digital phone lines', but technically, SIP Trunks are a little different. PSTN and ISDN phone lines are based on legacy landline networks, usiing physical in-ground wires and connections. This old-fashioned technology is only suitable for voice calls.

By contrast, SIP Trunks are a digital technology with no physical network to speak of. With SIP, your calls are delivered over the internet (DSL/ NBN / Ethernet) using the MyNetFone IP communications network. Moreover, SIP enables multimedia communications: voice, data and video. This makes SIP Trunks a future-proof option for forward-looking businesses.

So how does this apply to your business? Many organisations feel they've invested too much to get rid of their analogue PBX, but still want to use SIP Trunking. In such a case, MyNetFone provides a simple solution: an analogue-to-IP gateway device. This gateway can be connected to an analogue PBX and essentially converts PSTN and ISDN calls to SIP. 



How SIP Trunking works


When you make or receive a call, SIP Trunking turns that voice or video communication into 'packets' of data so it can be delivered using the internet.

The phone call is carried to its destination as data, before being received as an IP call or being converted back into an analogue phone call. (This will depend upon the recipient's network). Since a SIP-based call is transferred through the internet, without the costs of traditional networks, the call rates can be significantly lower. 


Why use SIP Trunks?


There are plenty of reasons to make the switch. SIP Trunking will cut business costs, prepare your communications for the NBN era and may improve the quality and scalability of your phone service. 



From small businesses to large enterprises, SIP trunks can easily be scaled to suit your needs. Because SIP trunks are virtual rather than physical, you can easily and inexpensively add or reduce the amount of channels. If service scalability is your primary concern, consider MyNetFone VoiceLink. This SIP Trunk plan provides an unlimited number of SIP channels - for a single low price.


Low switching cost

With SIP Trunking, you can save on CAPEX switching costs. In particular, MyNetFone SIP Trunks are interoperable with all major PBX brands. (See if your PBX is interoperable). MyNetFone has achieved full technical certification for deployments of Epygi QX phone systems, and the Microsoft Lync 2010 communications platform.

You can also connect analogue PBXs. A MyNetFone gateway solution will enable your PSTN or ISDN phone system to use modern SIP Trunks. This is a powerful way to extend PBX life and maximise the value of your PBX investment.



In the NBN era, SIP Trunks will be the global standard for voice communications. It’s a more affordable, more flexible communications system that has progressed with the advancements in broadband technology over the last decade. The traditional legacy landline network (copper) is being systematically replaced by fibre-optics (NBN). Business NBN is the building block for leaner, smarter and more modern business communications. So why not gain an edge on your competitors by implementing NBN-ready SIP Trunks?

Savings of up to 60%

Choosing SIP Trunking instead of traditional analogue PBX can save you up to 60% on your monthly phone bills.. MyNetFone SIP Trunk customers have made significant savings making the switch from analogue.

Where do savings come from? First, call rates are lower. Second, SIP Trunking can eliminate landline rental fees (when combined with Naked DSL broadband) by allowing you to get rid of lines / channels you don't need. With MyNetFone, channel capacity is shared across your entire organisation. So you get the ‘right’ amount of capacity – and only pay for what you need. (Compare this to ISDN services require you to purchase 10, 20 or 30 channels at a time. Not good value if you only need 12 SIP channels).


How to get started with SIP Trunks


What is required?


1. PBX or UC platform

SIP Trunking requires an existing PBX (MNF supports all major brands) or UC platform (eg. Microsoft Lync, 3CX). If your business does not have a PBX – you should consider the MyNetFone Virtual PBX service.


2. Internet

Customers usually combine SIP Trunking with an NBN or Ethernet internet service from MyNetFone. Very small (2-4 channel) SIP Trunk services can be delivered with an ADSL broadband connection. 


 3. Tame geek

A technical boffin will be needed to setup and configure your phone system for use with MyNetFone SIP Trunks. In some cases, new cabling and equipment will be required. (MNF cannot provide technical support or setup assistance for third-party PBXs. If you lack technical skills, we may be able to recommend a solution partner).


Things to know before you contact a SIP Trunk provider


1. How much capacity will you need?

SIP Trunk capacity is measured in channels and trunks. One channel = 1 call. On trunk = 1 location. Each trunk can support a number of channels / concurrent calls. SIP Trunking plans start at 2 channels and increase by regular increments up to 200 channels. A basic 2 or 4 channel service will suit a small office.

If your office is moving away from ISDN, you can directly replace those high-cost ISDN lines with a VoiceLink service. VoiceLink is a special kind of SIP Trunk that provides an unlimited number of SIP channels.

2. Do you want to keep your phone numbers?

MyNetFone is the only Australia carrier to offer free business number porting. This allows you to bring your existing phone, fax, 1300, 1800 and 13 numbers over to MyNetFone.




Do you have more questions about SIP Trunking? Ask us



Enquire online

Or call 1300 733 995