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.

Mobile IP is most often found in wireless WAN environments where users need to carry their mobile devices across multiple LANs with different IP addresses.

A common analogy to explain Mobile IP is when someone moves his residence from one location to another. Person moves from Boston to New York. Person drops off new mailing address to New York post office. New York post office notifies Boston post office of new mailing address. When Boston post office receives mail for person it knows to forward mail to person's New York address.

RFC 2002: IP Mobility Support
This is the IETF's RFC on Mobile IP edited by Charles E. Perkins, a Research Fellow at Nokia Corporation, in the Silicon Valley division of Nokia Research Center.

Tutorial: Mobile IP
Charles E. Perkins presents the Mobile IP standard in moderate technical detail and provides additional resources for further study.

Tools Simplify 802.11 Deployments
Wireless LAN installation is tricky. The construction of a facility and silent sources of RF interference impact the propagation of radio waves, often in odd ways.

Wi-Fi Planet
802.11 news, commentary and information.