The route does not have to be the same in both directions. Therefore, a mobile host needs to have a stable IP address in order to be uniquely identifiable to other Internet hosts. However, when a mobile host moves from one network to another, as shown in Fig. 1, the IP address of an MH will change due to the enforced hierarchical address structure of the Internet. If the MH has only standard IP stack in its operating system, the TCP connection will break up following this movement. (Mondal, 2003)
Mobile IP (Perkins, 2002) is the standard proposed by IETF to offer seamless mobile computing. Mobile IP extends IP by allowing a mobile computer to utilize two IP addresses: one for identification, and another for routing. For example, it enables a TCP connection to keep alive and re-route packets when the mobile host moves between points of attachment.
Mobile Host (MH): A host or router that changes its point of attachment from one network or sub network to another, without changing its IP address. A mobile node can continue to communicate with other Internet nodes at any location using its (constant) IP address.
In order to route data packets after MH has moved into its new location, MIP also defines simple mechanisms to deliver packets to the mobile node when it is away from its home network. ...