Mobile IP provides a network layer solution to the mobility problem, specifically for the Internet. It is independent of the underlying protocols at the data link and physical layers. Therefore, mobile IP can be employed over a variety of media choices including the use of wireless communications. Mobile IP addresses the use of a portable address similar to a person who is going on an extended vacation. The person going on vacation notifies the post office (PO) that he/she will be gone for several months. The new address for this individual is passed on to the postmaster in the local PO. The PO will forward all new incoming mail to the new address. When our vacationer returns, the mail stops being forwarded and the local PO is responsible to deliver the mail.

A similar process occurs in mobile IP. The mobile node (wireless data terminal device) is provided with a temporary address at the new location (foreign network or serving system). The mobile can obtain a temporary address from a foreign agent (an Interworking Function [IWF] of serving system) that provides these services or from another source. The mobile registers its temporary address with its home agent (IWF of home system) on its home network. A home agent keeps track of the current location of the mobile node.

When data packets are sent to the mobile node, they arrive at the home network. The home agent intercepts the packets and reroutes them to the mobile node s...