In a mobile communication scenario handover functions must be supported in order to keep connection alive switching between different points of access. Moreover, if the infrastructure is composed of different networks or technologies, intersegment handover is necessary to roam from a component to another. The handover function is implemented either for necessity or to improve performance. Necessity means that the terminal must perform a handover because its current network connection is worsening; in the other case switching to another network can help to achieve better performance even if the current network connection is fine. Furthermore, the handover can be soft or hard, according to the possible overlap in the connection of the two segments involved. This paper illustrates the behavior of TCP during intersegment handovers in an architecture including two segments: satellite and WLAN. In particular, the goal is to carry out a thorough analysis of a cross-layer based mechanism applicable during handovers to optimize the TCP performance. Such a mechanism is validated with an ad-hoc software simulator written in C++ and the most meaningful results are shown.