At Spitfire we believe that ensuring call quality is paramount when choosing any VoIP solution whether that is SIP trunks for an on-premise solution or a Cloud hosted PBX.


Any VoIP call is likely to cross multiple networks to reach its destination. To ensure call quality it is important to understand these networks and where possible be in control of their performance. Voice traffic is highly sensitive to poor network performance and unfortunately internet performance cannot be controlled. 

At Spitfire we realised that this is a complex concept to understand without detailed knowledge of carrier networks so we developed the CLEAR methodology to break down the complexities into easy to understand components.

Following the CLEAR methodology, Spitfire design VoIP services to ensure consistent voice quality, using our voice designated network, voice approved circuits and Quality of Service (QoS) mechanisms. Follow the links to find out more.


There are 5 key areas where voice traffic needs to be managed to ensure voice quality.

  • Customer Local Area Network (LAN)
  • Link – the data circuit from the customer premises to the existing ISP’s core network
  • Exit – how voice traffic is managed when it leaves the customer LAN towards the VoIP service provider
  • Arrival – how the voice traffic is managed from the VoIP service provider towards the customer LAN
  • Route – the networks that route the traffic between the VoIP service provider and the telephony networks