This paper presents LiTGen, an easy to use and tune open-loop traffic generator that statistically models IP traffic on a per user and application basis. From a packet level capture originating in an ISP wireless network, and taking the example of Web traffic, we show that the simple underlying structure of LiTGen is sufficient to reproduce the traffic burstiness accurately. In addition, the flexibility of LiTGen enables us to investigate the sensitivity of the traffic structure with respect to the distributions of the random variables involved in the model, and their possible dependencies.