DNS Tunnels are built through proper tools that allow embedding data on DNS queries and response. Each tool has its own approach to the building tunnels in DNS that differently affects the network performance. In this paper, we propose a brief architectural analysis of the current state-of-the-art of DNS Tunneling tools. Then, we propose the first comparative analysis of such tools in term of performance, as a first step towards the possibility to relate each tool with a proper behavior of DNS traffic. To this aim, we define an assessment of the tools in three different network configurations with three different performance metrics. We finally summarize the most interesting results and provide some considerations on the performance of each tool.