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Case Study : Tavistock Computer and Network Solutions – VoIP and 4G

Key Facts 

  • Netcelero Product: i-ctrl
  • Client: TCANS
  • Sector: IT Services
  • Location: Cornwall, England
  • Customer Since: 2021

About Tavistock

Tavistock Computer and Network Solutions (TCANS) are a one-stop shop for CCTV, data networking and IT services. Supporting diverse customers across Devon and Cornwall, their broad expertise enables them to design and deliver individually targeted digital solutions.

The Challenge

Netcelero was contacted by Tavistock Computer and Network Solutions whose client’s remote office in the Southwest of England, were experiencing connectivity issues due to their rural location and lack of fibre available to them. TCANS understood they needed a bespoke solution that would enable them to use 4G to support their business needs as well as their VoIP (Voice Over Internet Protocol) phone system. 

The customer was experiencing many issues with their VoIP calls, with calls being dropped intermittently – this was frustrating for the business and their customers – a long term reliable solution was needed and fast.  

The in-situ office network did not have sufficient bandwidth to support the office needs and run the VoIP system. On top of this, using VoIP over a 4G connection is very problematic due to 4G having a dynamic IP (not a fixed IP) and because of how Voice over Internet Protocol works. 

Without getting too technical, VOIP is UDP based and uses a technique called firewall UDP state holding to allow inbound calls. In traditional DSL or fibre connections, your public IP is on your office/home router with a full range of ports for states to be created on, and with reputable firewall appliances, you can set long time outs on these UDP states, that the VOIP phones are creating.   

However, in cellular communication (4G, 4G+) you have carrier NAT, and the public IP is in the core of the ISP, not at your modem. To further complicate things, you are granted only 500 states, which means that states quickly expire, rather than being held open (as they are in the DSL/fibre setup) resulting in dropped calls. 

To resolve the VoIP issue, which was impacting productivity and customer support levels, the client needed to address two key issues – faster broadband speeds and a fixed IP. They needed a bespoke solution that would support 4G+ while also providing them with a full public IP regardless of the 4G Mobile Network SIM they selected. 

TCANS knew the standard 4G speeds in the location were likely to be insufficient, however because they are the telecommunication experts in the Devon and Cornwall area, they knew that 4G+ was available, offering download speeds of 100Mbps and uploads speeds of 20Mbps . However, as 4G+ (and naturally standard 4G) do not provide a public IP this was not a viable option for the business as an easily managed consistent internet connection.  

The Solution 

A Netcelero i-ctrl, a plug and play solution which simplifies secure improved connectivity, was installed at the customer’s remote office. All that the TCANS technical team had to do then was simply plug the 4G+ router in to the i-ctrl device, and instantly they had access to a public IP on this high speed 4G+ connection. 

By putting the VoIP calls through the Netcelero tunnel, the customer had a full public IP with more normal state rules, so that the VOIP phones could hold the states open and thus receive VOIP calls – NO MORE DROPPED CALLS. 

By installing the i-ctrl solution, the TCANS technical team can now also remotely monitor and make any system changes or upgrades required remotely, enabling them to proactively respond to any issues. The project has delivered excellent customer satisfaction for TCANS, with minimal requirement for them to visit the site – and in the process has significantly reduced their carbon footprint and their fuel costs. 

Netcelero enables IT providers to offer flexible networking solutions for remote sites or branch offices. Our ‘secure connectivity as a service’ combines internet connections (including 4G… or even just 4G) enabling them to offer a bespoke solution to meet their client’s individual connectivity needs, no matter where the site is located – even unmanned remote sites or branch offices where there may be no dedicated IT footprint on site. 


As well as enjoying the operational benefits a super-fast broadband connection provides, the customer now has peace of mind that they have a VOIP system they can rely on and do not have to worry about constant dropped calls that often result in reputational damage and lost revenue due to missed opportunities.  

They also have the option of adding a secondary connection, such as Starlink, to eliminate downtime, improve network security and many other business critical benefits.