DNS continues to be a significant component of our Internet core and it is no surprise that it has a high adoption rate within the modern telecommunications industry. In this talk, Arber will guide you through building your own DNS server using NAPTR records to return least cost routes to the DNS client, using only open-source technologies like CGRateS on server side and dig on client one. CGRateS is a battle-tested Enterprise Billing Suite and Routing System with support for various prepaid and postpaid billing modes.