In either case, this process allows a mobile node to identify mobility agents, obtain one or more care-of addresses, learn about any special services provided by a foreign agent, and determine whether it is connected to its home network or a foreign one. A mobile node starts out on its home network. While attached to the home network, the node is registered with the home agent and operates normally using its home address. As the mobile node roams, it will be connected to a series of one or more foreign networks. This process provides a binding between the home and care-of addresses, and defines the lifetime of the registration.
Encryption is used to authenticate the registration information.
The mobile node eventually returns home after being registered on a foreign network. At that time, the node has to deregister the foreign network information with the home agent. Mobile nodes need to be able detect to what network the are connected as they roam from network to network. The simplest mechanism is based upon the registration lifetime, mentioned above. As long as a node stays on a foreign network, the registration will be periodically renewed.