IPv6 Mobility - Internet Protocol version 6 (IPv6)

Explain IPv6 Mobility

An IP address is essential for a host when it is connected to a link or a network and all communication takes place using that IP address. When the host changes the physical location and moves into another area/ subnet/network or link, then the IP address changes and all the communication that take place on the host with the previous IP address, goes down.

A mechanism to roam around different links is provided to the host by IPv6 mobility without losing the communication and the IP address. This technology includes multiple entities such as:

• Mobile Node: The device that needs IPv6 mobility.
• Home Link: The link provides the home address for Mobile IPv6 and the link is configured with the home subnet prefix.
• Home Address: The address which is acquired by the Mobile Node from the Home Link is the Home Address. The communication takes place as usual if the mobile node remains in the same Home Link.
• Home Agent: A registrar for Mobile Nodes is Home Agent. The information about all Mobile Nodes, Their Home Addresses and the IP addresses are maintained by Home Agent connected to Home Link.
• Foreign Link: Any other Link that is not Mobile Node’s Home Link.
• Care-of Address: A new IP address of the Foreign Link’s subnet is acquired when a Mobile Node gets attached to the Foreign Link. The information of both the home address and care-of address is maintained by the Home Agent. To a single mobile node, multiple care-of addresses can be assigned but only one care-of address bind with the Home Address.
• Correspondent Node: Any IPv6 enabled device that intends to have communication with Mobile Node.

How Mobility is operated in IPv6?

All the communication takes place on home address when the Mobile Node stays in its Home Link as depicted below:

When the Mobile Node gets connected to some Foreign Link, leaving the Home Link, the mobility feature of IPv6 comes into action. An IPv6 address from the foreign link is acquired by the Mobile Node, once it gets connected to a Foreign Link. The address is known as the Care-of Address. The binding request is sent to the mobile node and the Home Agent connects with the Care-of address and thus a tunnel is established between both of them.

The Home Agent intercepts the packet and is forwarded to the Care-of Address of the Mobile Node over the Tunnel to establish a connection with the Mobile Node on the Home Address.

Route Optimization

When a communication is initiated by sending a packet to Mobile node to the Home Address the Home Agent tunnels these packets to the Mobile Node. But Through Route Optimization, when a packet is received by Mobile Node the replies are not forwarded to the Home Agent but the packets are directly sent to the Corresponding Node and use the Home Address as the Source Address.