3.1 Mobile IPv6 basis

Mobile IPv6 specifies how the mobil devices should act using IPv6. Every mobil device is identified by its Home Address, independently where it is situated in Internet.

When the Mobile Host is away from its Home Network, it acquires a new care-of address. The IPv6 packets sent to the Home Address are routed to its new care-of address.

Main differences between Mobile IPv4 and Mobile IPv6:

• The Route Optimization concept in Mobile IPv4, in Mobile IPv6 is part of the own protocol.

  This means that packets sent from the Correspondent Node to the Mobile Node directly go to the Mobile Node without going first to the Home Agent and then from the Home Agent to the Mobile Node.

• In Mobile IPv6, the packets sent by the Mobile Node, in their source address is specified the care-of address, and in the optional headers is specified the Home Address. This makes the packets are routed transparently to routers and to the upper layers.

• Using the Care-of address as source address makes easy to route multicast packets sent by the Mobile Node.

  In Mobile IPv4, the Mobile Node establishes a tunnel with its Home Agent to be able to use its Home Address transparently as source address of its multicast packets.

  In Mobile IPv6, using the optional IPv6 Rounting Header, makes the packet routing compatible with multicast routing.

• In Mobile IPv6, the Foreign Agents are not necessary anymore. The Mobile Node uses the IPv6 features like address autoconfiguration and Neighbour Discovery.

• The packets sent by the Mobile Node when it is in the Foreign Network don't need be encapsulated (like in Mobile IPv4). They use the IPv6 Routing Header so the number of bytes transmited are reduced.

• When the Mobile Node isn't in the Home Network, the Home Agent intercepts every packet sent to the MobileNode using IPv6 Neighbour Discovery rather than ARP (Address Resolution Protocol) like in Mobile IPv4. This makes easy the Mobile IPv6 implementation because it is independent from the link layer.

• The dynamic Home Agent address' discovery mechanism in Mobile IPv6 uses IPv6 anycast and returns only one reply to the Mobile Node. Mobile IPv4 uses broadcast messages and a reply for every Home Agent.