Data transfer in mobile networks has increased significantly over the past years, and the capacity of these networks has grown accordingly. Due to their different set of characteristics compared to wired networks, they have also received attention from end-to-end developers on transport and application level. However, there exists no research on packet reordering in modern mobile networks, and how a transport layer should be designed to cope with it. In this paper we discuss how to measure packet reordering in mobile networks with the help of TCP. Our analysis in Finnish mobile networks shows that reordering characteristics depend heavily on the operator, but is present in all tested networks, and negatively impacts TCP when not handled. We find that both number of reorderings in a connection and the extent of the reordering is influenced by the sending rate. Additionally, we present the framework for a reordering prevention algorithm which takes into account the findings by automatically adapting to the current sending rate.