IPv6 Mobility Components

IPv6 mobility consists of the following components,

• Home link: The home link is the link that is assigned the home subnet prefix. The mobile node uses the home subnet prefix to create a home address.
• Home address: A home address is an address assigned to the mobile node when it is attached to the home link and through which the mobile node is always reachable, regardless of its location on the IPv6 Internet. Packets addressed to addresses matching the home subnet prefix are delivered to the home link using normal IPv6 routing processes. If the mobile node is attached to the home link, IPv6 mobility processes are not used and communication occurs normally. If the mobile node is away from home (not attached to the home link), IPv6 mobility processes are used to either deliver or tunnel traffic addressed to the mobile node's home address to its current location on the IPv6 Internet. Because the mobile node is always assigned the home address, it always has a virtual connection to the home link. This relationship is shown in Figure 12-1 as the Virtual Mobile Node.
• Home agent: The home agent is a router on the home link that maintains an awareness of the mobile nodes of its home link that are away from home and the addresses that they are currently using. If the mobile node is on the home link, the home agent acts as an IPv6 router, forwarding packets addressed to the mobile node. If the mobile node is away from home, the home agent tunnels data sent to the mobile node's home address to the mobile node's current location on the IPv6 Internet.
• Mobile node: A mobile node is an IPv6 node that can change links, and therefore addresses, and maintain reachability using its home address. A mobile node has awareness of its home address and the global address of its current link address, and indicates its home address/current link address mapping to the home agent and IPv6 nodes with which it is communicating.
• Foreign link: A foreign link is a link that is not the mobile node's home link. A foreign link is assigned a foreign subnet prefix.
• Care-of address: A care-of address is an address used by a mobile node while it is attached to a foreign link. The care-of address is a combination of the foreign subnet prefix and an interface ID determined by the mobile node. A mobile node can be assigned multiple care-of addresses; however, only one care-of address is registered as the primary care-of address with the mobile node's home agent. The association of a care-of address with a home address for a mobile node is known as a binding. Correspondent nodes and home agents keep information on bindings in a binding cache.
• Correspondent node: A correspondent node is an IPv6 node that is capable of communicating with a mobile node while it is away from home. A correspondent node can also be a mobile node.