What do you know about handoff or handover process? and how about LCS(Lazy Cell Switching), ESC(Eager Cell. Switching) ?

The term handover or handoff refers to the process of transferring an ongoing call or data session from one channel connected to the core network to another. 

Using lazy cell switching the mobile node waits until the lifetime of its registration expires and then tries to reregister or discover a new foreign agent to register with.

Using eager cell switching the assumption is that the mobile node is moving towards the new cell, therefore the best strategy is to register with a foreign agent of that cell as quickly as possible. The strategy is to register with new foreign agents as soon as they are discovered. This makes it possible to maintain a constant connection to the Internet. Provided that there is constant network coverage of course. Care has to be taken to avoid a mobile node in range of two foreign agent switching back and forth. This can be done by maintaining a list of the latest foreign agents. To permit the mobile node to switch back, the data on this list has to expire rather quickly.