<< Back to Know-how blog  |   4 Minute Read    |   Topic: [SIP Trunking]

What are the benefits of SIP Trunking?

What are the benefits of SIP Trunking

SIP trunking is the obvious choice when it comes to replacing your ISDN circuits. But, with the ISDN switch off not due until 2025, it’s important to understand the business benefits you can leverage today. Realising why SIP trunking is superior to PSTN and ISDN connectivity is a key element when it comes to enhancing the business case to migrate to SIP trunks today - rather than leaving it another year.

Ongoing costs

SIP providers always mention the incredible savings when discussing the benefits of SIP trunking. And rightly so. The typical comparison is ISDN vs SIP. When evaluating SIP cost benefits against ISDN, the preference for SIP becomes clear.

A typical ISDN line costs more than £15 per month – and must be purchased in pairs. That’s a minimum of £30 per ISDN pair, in contrast to just pounds per month for a SIP trunk with the associated concurrent calls. As businesses grow, more ISDN circuits are required. That’s an average of paying 8 times the price of a SIP trunk per month, for a lesser service.

ROI from day one

When installing an ISDN circuit, the average lead time is around 20 working days and costs around £250 per pair. With SIP trunks, you can expect a 5 working day lead time and no up-front charge for configuration of new or additional SIP trunks.

Upon adding additional users to a business, the return on investment is immediate compared to ISDN. In the first month, inclusive of one off charges, you are likely to save £250 for installation and at least £20 in the monthly costs – per 2 channels of SIP that you add.

Reviewing purely from a cost perspective, the business case for SIP over ISDN sees cost as a hugely decisive factor.

Cloud functionality

Aside from the obvious cost benefits, you will experience the advantage of basic cloud functionality. SIP trunks come with built in disaster recovery scenarios, alternative routing and simple administration.

With any SIP trunk, you can failover to a backup SIP trunk hosted at another site, in another data centre or simply connected to another internet connection. This gives you peace of mind if your SIP trunk fails due to connectivity, power or natural disaster. You can automatically failover to a secondary service without the need for manual interjection.

SIP trunking also provides the ability to divert specific numbers to alternative destinations in the case of failure. Calls can be automatically routed to a specified number when the call cannot connect, a user is busy or if the required destination cannot be reached after set amount of time.

Digital transformation

Digital transformation is a key factor in most business strategies. As businesses edge towards digital transformation, adopting cloud communications is key. The first step in cloud communications is SIP trunking.

When business do not have the immediate need to move to cloud telephony, like when the PBX serves current functionality requirements, SIP trunks can replace the phone lines. There is no case to keep ISDN lines when looking at cost, risk or functionality. Migration from ISDN to SIP is a simple shortcut to give your business one foot into the door of cloud communications. Once SIP has been adopted, the transition to full cloud telephony becomes easier to achieve, when the time is right.

Easy administration

When your phone lines have been migrated to SIP, management and administration of your SIP service is easily accessible. With any SIP service, you can expect a browser based portal to login and access all your phone numbers and SIP trunks.

With a few clicks, you can setup business continuity plans, overflows for peak periods and personal preferences for DDIs.


As your business grows, it’s vital that your telephony can grow with you. With traditional ISDN or PSTN services, each time you add a user, you need an additional phone line. This involves both an expense and an extended wait time.

With SIP services, a new user can be added within minutes through self-service portals and SIP channels can be extended as and when required.

The same is true if your business undergoes periods of consolidation or experiences seasonal shrinkage. When users leave the business, it makes no sense to keep paying for services that you no longer require. SIP enables you to scale down in line with business change or seasonal shifts. 

Global availability

SIP supports your organisation’s need for fast growth across multiple geographic locations. By combining your voice and data into a single network, your distributed locations and remote workers can be consolidated. The scalability of SIP allows you to scale as you open new sites or move to a remote working model.

Whether your users are in a different section of the office, area code or country, SIP provides local presence as per your requirements. If you have employees in other countries that require a local number, SIP is not dependent on location to provide the area code. This means your New York office could utilise your London numbers if you so wish.

Whether your requirement is simply to save money or enable transformation either digitally or globally, SIP is a great first step. Now you know the benefits of SIP trunking, why not reinforce your decision by checking out the future of SIP trunking?

New call-to-action
We'd love to talk to you about how we could help your business.

Answer a few short questions and we'll get in touch with you!

Get in touch!

Recent posts

Don't forget to share this post!