It’s already been two years since BT announced that they were ceasing Integrated Services Digital Network (ISDN) in 2025. This might seem a long way off, but with millions of customers still to migrate and little further investment in existing ISDN lines likely to take place, switching to more sophisticated Session Initiation 


Protocol (SIP) technology should be seen as a priority for any IT Manager. 


In the past this was a job for the telecoms department, however this role is now predominately being covered by the IT Manager. A recent survey by telecoms analysts found that over 52% of IT Managers now also have responsibility for telecoms. In spite of this, the same survey revealed that nearly 70% of IT 


Managers have heard of SIP, but don’t know or fully understand what SIP is, despite it being the next big product in telecoms. 


Landlines now make up less than 30 percent of UK voice telephony connections according to Ofcom, being replaced instead by more sophisticated and cost-effective technology. 



SIP trunking is a form of Voice over Internet Protocol (VoIP) and streaming media service based on the Session Initiation Protocol (SIP). This has enabled telephony providers to deliver voice traffic via an internet connection, rather than traditional telephone lines. SIP can run multiple software applications such as voice, video, and other streaming media applications, for example desktop sharing, web conferencing, and shared whiteboard solutions. 


“Elements such as call recording, voice mail, intelligent Disaster Recovery (DR) call plans and other features are beginning to appear as network services, and this trend is set to continue and accelerate as service providers look to differentiate themselves from each other and align services to the trunk itself as opposed to separate platforms, the PBX or even hosted provision.”
Paul Wakefield, SIP Product Manager, Gamma




As you can imagine, in a revolutionary digital age transferring voice and media communications to an internet based platform provides many benefits. 


  • Keep the same geographic number when moving offices with no call forwarding costs.
  • Add lines, take them away, split calls, make changes easily – you’re in control.


• Continue working if you have to relocate temporarily in an emergency. 

• Cut back on the number of lines your business needs and reduce the number of PBXs you need to maintain whilst still keeping full control of your telephony. 

• Reduce costs – cheaper connectivity than ISDN, up to 25% cheaper calls, free internal calls and up to 50% lower line rental costs. 

• Great call quality and business-grade resilience. 

• Compatible with Skype for Business and other conferencing solutions. 


SIP trunking is a very flexible and powerful form of communication. It’s a solution that enables businesses to streamline their communication costs and resources by routing calls through internet circuits as opposed to the more traditional ISDN lines. SIP lines can be up and running in minutes with a substantially reduced setup fee. ISDN can take weeks to install, with a significantly higher install cost. SIP’s key feature is that it runs over a data circuit, so the removal of the physical ISDN phone lines makes it much easier to manage and implement. 


SIP is delivered via an Assured Data Circuit, which makes it a ‘virtual’ phone line rather than physical wires of ISDN. SIP is highly scalable and calls are typically up to 50% cheaper than traditional ISDN lines. Whilst the SIP trunking market growth has been steady. Around 400,000 ISDN channels will be converted to SIP this year, and there are already over 1.6 million SIP channels in the UK. By 2025, BT has a goal to migrate all end users from its ISDN network to an all- IP network. 


But it’s not just the cost savings that make SIP such an attractive proposition, it also offers a level of flexibility that traditional ISDN simply can’t provide. As workforces continue to gravitate towards more flexible working patterns, the demand for office solutions on the move is only going to increase over the next ten years.


SIP enables employees who are working remotely to have calls made to their desk phone automatically delivered to their smartphone or PC, without incurring any forwarding charges. 


This also applies if the line is busy, or if an office is hit with an unforeseen event, like a local network failure, severe weather or fire damage. SIP trunking minimises these problems, allowing a business to keep working through every eventuality. So let’s not underestimate the importance of that. A recent survey found that for 63% of respondents, it would take less than two hours of being unable to make or receive calls before a business suffered reputational or financial damage. 




A good data connection is essential in order to run a SIP solution effectively and to make the most of all the additional benefits that come with it. We can easily identify if your current internet connection can support a SIP solution and can recommend the best package for you. 



SIP is going to play a pivotal role over the next 10 years in setting the future proof functionality of voice, video and media collaboration. Many business are unprepared for the changing communications requirements, but we can help. 


Contact our solutions team on: 0113 467 1606 or [email protected] to discuss the benefits of SIP Trunking.