1. Postal mail is sent to you by placing a letter (the packet payload) in an envelope addressed to you (IP header).

2. The letter arrives at your local post office and is routed to you at your Home Address, as shown in Fig.

3. When you move, you tell the local post office (Home Agent) to forward packets to your new location (Care-of Address [CoA]). Now, when a letter addressed to your Home Address arrives at your local post office, it can now be readdressed (tunneled) to your new location (CoA).

4.The letter then arrives at the post office that services your new location (Foreign Agent [FA]) and is delivered to you at your new location (CoA), as shown in Fig. This mail delivery is done with no effort by the original sender of the letter.