1. An IP (Internet protocol) handoff method involving mobile agent platforms having border lists and visitor lists comprising: receiving an IP handoff registration request message from an FA (foreign agent) of an MN (mobile node) by a first mobile agent platform (MAP) having a first MAP region and determining whether or not the MN moves in the first MAP region and wherein the FA is located in the first MAP region; when it is determined that the MN moves from a second MAP region, transmitting a message for requesting to add an entry of the MN to a border list of a second MAP in the second MAP region; and when it is determined that the MN moves in the first MAP region and the FA is adjacent to the second MAP region, transmitting a message for requesting to add the entry of the MN to the border list of the second MAP, wherein the first MAP region and the second MAP region are two separated MAP regions.