The present invention concerns a method for optimizing ROHC RTP (Robust Header Compression Real Time Protocol) compression applied to IP header of data packets stream so as to use more compact formats enable to remain in a steady state, to never discard received packet, and to serve radio resources without requiring to modify ROHC specification. In the method, when handover or mobility procedure is started, new reference values are normally added to a sliding compression window, but no reference value is removed from the window as long as the handover or mobility procedure is on going. After the handover or mobility procedure is complete, when the number of values transmitted on the new radio link are appropriate to cope against the error properties on the new link, all older values can be removed at once from the compression window, thereby reverting to normal window operation.