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SIP Trunks allow office or cloud based communication systems to connect to the Public Switched Telephone Network. The use of network bandwidth in the form of a broadband service or direct internet access link enables closer integration with IT infrastructure in the new converged world of communications.



  • Moving to SIP trunking not only provides you with the flexibility to take your calls where you want to but it also has significant financial benefits. SIP trunks are much cheaper to rent than current ISDN30 or analogue lines and capacity can easily be adjusted according to demand.
  • Being connected to the SIP service normally provides you with cheaper call rates and even free calls between your own sites.
  • Disaster Recovery and Service Resilience are enhanced by the ability of the SIP platform to automatically re-route calls in the event of an infrastructure problem. This includes re-routing full DDI ranges to an alternative SIP trunking point, which cannot be done with ISDN30
  • SIP telephone numbers are not geographically dependant enabling an existing geographic number to be answered anywhere (including abroad!). This allows great flexibility for home working, disaster planning and office relocations.


SIP trunks have been available for some time but they have previously suffered from quality and connectivity issues. However, many of the issues have now been resolved by prioritising voice services in the network and enabling SIP trunking over diverse or resilient routes. In fact, SIP trunking is far more flexible than ISDN30 or analogue services during infrastructure problems as it can re-route to an alternative destination with the entire number range, including full DDI. Whether your existing communications system is a legacy one or server based, this facility can significantly improve system performance.


We provide SIP trunking as an authorised reseller of Spitfire Networks. The choice of delivery mechanism will depend on the number of trunks you need and can range from a dedicated SDSL service to a combined DIA and SIP trunk with voice prioritisation.

The service is delivered to a managed router on site where we engage with your communication system provider to connect to your system. We will arrange for any new numbers to be delivered and old numbers ported (where possible). We will also test the DR element which if a second internet route is not available, can be to alternative 'dialled' destinations, including mobiles.

SIP trunking now does away with the relationship of telephone number to geographic position. This has two main benefits, firstly that you can take your published number to any office location you wish (for example, if you move your London office to Birmingham, you can keep your London Number) or you can be allocated a new number in an area of your choice!


Link to information sheet