Mobile IP introduces the following new functional entities:
Home agent (HA) – Router or server on the home network of a mobile node. The router intercepts datagrams that are destined for the mobile node. The router then delivers the datagrams through the care-of address. The home agent also maintains current information on the location of the mobile node.
Foreign agent (FA) – Router or server on the foreign network that the mobile node visits. Provides host routing services to the mobile node. The foreign agent might also provide a care-of address to the mobile node while the mobile node is registered.