When we connect a terminal to the network, it will get an IP address and all the communication will be based on that particular IP address.

When the terminal changes its physical position , then the IP address associated to that changes accordingly.

IPv6 mobility provides a mechanism for the host to roam around different links without losing any communication/connection and its IP address.

Multiple entities are involved in this technology:

• Mobile Node: The device that needs IPv6 mobility.

• Home Link: Home link is the user address or the terminal address.

• Home Address: This is the address which the Mobile Node acquires from the Home Link. This is the permanent address of the Mobile Node. If the Mobile Node remains in the same Home Link, the communication among various entities take place as usual.

• Home Agent: This is the ISP of the user.

• Foreign Link: When the user changers location then the service will be provided by the foreign agent of that location.

• Care-of Address: When a Mobile Node gets attached to a Foreign Link, it acquires a new IP address of that Foreign Link’s subnet. Home Agent maintains the information of both Home Address and Care-of Address. Multiple Care-of addresses can be assigned to a Mobile Node, but at any instance, only one Care-of Address has binding with the Home Address.

• Correspondent Node: Any IPv6 enabled device that intends to have communication with Mobile Node.

Mobility Operation

When Mobile Node stays in its Home Link, all communications take place on its Home Address as shown below:

When a Mobile Node leaves its Home Link and is connected to some Foreign Link, the Mobility feature of IPv6 comes into play. After getting connected to a Foreign Link, the Mobile Node acquires an IPv6 address from the Foreign Link. This address is called Care-of Address.

The Mobile Node sends a binding request to its Home Agent with the new Care-of Address. The Home Agent binds the Mobile Node’s Home Address with the Care-of Address, establishing a Tunnel between both.

Whenever a Correspondent Node tries to establish connection with the Mobile Node (on its Home Address), the Home Agent intercepts the packet and forwards to Mobile Node’s Care-of Address over the Tunnel which was already established.