SIP Trunking Explained

Anna Sopova

It sounds complicated, but SIP trunking is quite a straightforward concept. It’s a method for businesses to replace their traditional phone lines with an internet connection. SIP providers are like phone companies - except with a SIP connection, the phone lines they provide are accessed over the internet.

Keen to see cost savings in your communications budget? SIP trunking services are usually 60-80% less than traditional phone line services!

So, what is a SIP trunk? If you’re going to make the jump to Session Initiation Protocol, then you need to understand how it works. Want some context so you can make an informed purchase? No problem! We’ve got you covered.

What is SIP Trunking?

Session Initiation Protocol trunking enables a business to convert their PBX (Phone Exchange System) to send and receive calls over the internet. All types of applications are allowed, so SIP technology covers voice, video and messaging connections. That means streaming is supported - so desktop sharing, web conferencing and shared whiteboard are all possible with a SIP system.

Session Initiation Protocol itself is the standard communications protocol for voice and video in a Unified Communications solution across a data network.

How does it work?

With SIP trunking, there is no physical wired connection to a phone company. Instead, the on-site PBX connects via a virtual trunk over your business’ existing internet connection. That means there are no longer any analogue phone lines connected to your business premises - just a trunk connection between your PBX (your private telephone network) and the internet.

The existing traditional Public Switched Telephone Network (PSTN) using analogue lines is to disappear, replaced by the more flexible Session Initiation Protocol trunks. All the main phone companies (like Verizon and BT) are phasing out ISDN and moving to IP. In short, all phone line trunks will be delivered over IP using SIP protocol.

Phone numbers are linked to the virtual trunking functionality, not the office, so you can move offices and retain the same number. You can also bring your existing phone numbers to the virtual trunking system.

Benefits of SIP trunking

Because your business doesn’t need to maintain incoming phone lines, there is a dramatic reduction in cost. The costs savings are realised both through the elimination both of IT costs in maintenance and the charges for incoming lines.

Even better - your business will also see the end of high phone bills and long distance charges. With trunking you will only pay for the number of lines you need, so you will no longer be locked into contracts with excess analogue lines.

Because your connection is virtual, it’s easy and fast to add or remove lines or modify the service.

The quality of SIP networks is much more reliable than traditional analogue services. Here’s why: trunking service providers will be able to reroute your services in case of an outage to a redundant data line, or forward the PBX to your company’s mobile phones. You will be reconnected in minutes, meaning you never miss important calls.

SIP trunking costs are further reduced because you can retain your existing phones and phone numbers. You can apply any numbering format you require - meaning you can have a local area code, projecting a local service.

SIP trunking considerations

You might still have a few questions on understanding SIP trunks. It’s true, any change to your phone connections is a significant factor, and you need to make sure the decision is right for you. These are a few of the most common questions, with helpful answers:

  • How do I find out about the SIP trunking price for my business?

    If you want to buy SIP trunking, you need to contact a reputable trunking provider. You will generally be charged a monthly fee. This varies depending on the number of channels you need. This allows you to add or remove channels easily but provides a fixed monthly cost that only varies when you make changes.

  • How many SIP trunks do I need?

    This depends on the size of your organisation. Generally, not all your employees will need a phone connection at the same time - so you can use a ratio of 3:1 (1 call path for every 3 employees). Your Session Initiation Protocol provider will help you calculate exactly how many trunks you need for the desired number of phone paths.

  • Is my network ready for SIP trunking?

    You will need to work closely with your SIP provider to ensure your network has sufficient bandwidth, quality of service and firewalls. The bandwidth is especially crucial because Session Initiation Protocol means your network will need to be able to support your entire phone system, as well as the existing internet connection. Quality of Service (QoS) prioritises your voice traffic to ensure your calls get the required bandwidth, regardless of what other pressures are on the network at that time.

  • Are SIP systems safe?

    You will need to configure your firewall to work correctly with SIP trunking. You will also need to enable emergency call, by adding Enhanced 911 functionality.

Next steps… get ready for SIP trunking

There are a few ways to reduce your business phone bills, and Session Initiation Protocol is an excellent option for reliability and scalability.

If you want to realise these cost savings, then you need to get in touch with a SIP trunking provider. Make sure they can work with you to provide a service that meets your demands, with the capability to scale up or down as your organisation needs it. They should be able to advise you on your network considerations, such as bandwidth and QoS requirements. And they should offer fast service to add capacity. Most importantly, you should see a dramatic cost saving versus your existing analogue phone service provider.

Be ready to analyse your phone usage and organisation activities, so you can be a knowledgeable buyer and choose the right service for your business.

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