The growth of the wireless Internet has led to the optimization of network protocols to provide for a better performance. Most of the Internet traffic uses TCP, the de facto transport layer protocol. Unfortunately, TCP performance degrades in the mobile and wireless environments. A good amount of research has been attempted to improve its performance in the unpredictable mobile and wireless environments where link disconnections, packets losses and delays are common. Most of these proposed solutions target the case where the mobile host acts as a TCP receiver. For various reasons, almost none of the solutions have reached the stage of deployment. In this paper, we propose an interlayer collaboration model for TCP performance improvement in mobile and wireless environments. We specifically target the case where a mobile acts as a TCP sender. ILC-TCP is an end-to-end approach and does not need any special support from the base station infrastructure. ILC-TCP is evaluated against the normal TCP in various scenarios. Performance results suggest that ILC-TCP performs better than the normal TCP in many scenarios involving long disconnections, frequent disconnections and in the scenarios where a mobile host moves at considerable speeds. © 2003 IEEE.