There are two possible modes for communications between the mobile device and a peer device.
Bidirectionaltunneling – is available even if the mobile device has not registered its current binding with the peer device.
Packets from the peer device are routed to the HomeAgent and then tunneled to the mobile device.
Packets to the peer device are tunneled from the mobile device to the HomeAgent (reverse tunneled) and then routed normally from the home network to the peer device.
Routeoptimization – requires the mobile device to register its current binding at the peer device.
Packets from the peer device can be routed directly to the care-of address of the mobile node.
When sending a packet to any IPv6 destination, the peer device checks its cached bindings for an entry for the packet's destination address. If a cached binding for this destination address is found, the device uses a IPv6 routing header to route the packet to the mobile device by way of the care-of address indicated in this binding.