How to generate realistic network traffic?

Network engineers and designers need additional tools to generate network traffic in order to test and evaluate, for instance, application performances or network provisioning. In such a context, traffic characteristics are the most important part of the work. Indeed, it is quite easy to generate traffic, but it is more difficult to produce traffic which can exhibit real characteristics such as the ones you can observe through the Internet. With the lack of adequate tools to generate data flows with realistic behaviors at the network or transport level, we needed to develop our tool entitled SourcesOnOff. The emphasis of this article is on presenting this tool, explaining how we implemented it and outlining the methodology it follows to produce traffic with realistic characteristics.