Mobile IP is a standard that allows users with mobile devices whose IP addresses are associated with one network to stay connected when moving to a network with a different IP address. Mobile IP provides an efficient, scalable mechanism for node mobility within the Internet. Using Mobile IP, nodes may change their point-of-attachment to the Internet without changing their IP address. This allows them to maintain transport and higher-layer connections while moving. Node mobility is realized without the need to propagate host-specific routes throughout the Internet routing fabric.
When a user leaves the network with which his device is associated (home network) and enters the domain of a foreign network, the foreign network uses the Mobile IP protocol to inform the home network of a care-of address to which all packets for the user's device should be sent.
The Mobile IP protocol enables nodes to move from one IP subnet to another. Each mobile node is always identified by its home address, regardless of its current point of attachment to the Internet. While situated away from its home, a mobile node is also associated with a care-of address, which provides information about its current point of attachment to the Internet. The protocol allows registration of the care-of address with a home agent. The home agent sends datagrams destined for the mobile node through a tunnel to the care-of address. After arriving at the end of the tunnel, each datagram is then delivered to the mobile node. It can be used for mobility across both homogeneous and heterogeneous media. Mobile IP defines a set of new control messages, sent with UDP, Registration Request and Registration Reply.
Mobile IP Terminology:
Mobile Node (MN): A node capable of performing network roaming
Home Agent (HA): IP address of the mobile node's home agent (such as a router).
Foreign Agent (FA): IP address of the mobile node's foreign agent (such as a router).
Care of Address (CA): Address of the end-of-tunnel towards the mobile node
Correspondent Node (CN): The other node that the MN is communicating with
Home Address : Mobile’s permanent IP address
Mobile IP References: