#8) IPv6 offers better mobility features than IPv4
When we consider IP mobility features we are essentially considering features that
would be useful for:
Mobile devices, which can change their location but would like to retain existing connections.
Mobile networks that provide mobility to a group of devices
Ad-hoc networking in which some of the devices stay connected to the network or in the vicinity of the network only for the short duration of a communications session
When a mobile node is not at home, it conveys information about its present location, also called, care-of-address to the home agent. Now if a node wants to communicate with this mobile mode, it will first send the information packets to the home address. The home agent receives these packets and using a table, sends these packets to the care-of-address of the mobile node.
Challenge to IPv4
Mobile IPv4 requires a special router in the location of the mobile node to properly receive calls. Also, route optimization is available to mobile IPv4 only through an optional set of extensions. There is also an ingress filtering problem in mobile IPv4 since the correspondent node uses the home address as the source address of the packet and there may be confusion on which IP addresses it should be allowed to accept or not.
How does IPv6 provide a solution?
With IPv6, mobility support is mandatory by the use of Mobile IPv6 (MIPv6). Route optimization is a built-in feature for mobile IPv6. Further, features like Neighbor Discovery and Address Auto-configuration allow mobile nodes to function in any location without needing the services of any special router.
MIPv6 can be used to achieve seamless mobility by allowing handovers between different access technologies say from example from a cellular network to a wireless network, with minimum interruption to ongoing connections. There is no ingress-filtering problem in Mobile IPv6 because the correspondent node uses the care-of address as the source address.
These devices increasingly demand delivery of converged voice, video and data, which is made possible through a standard called the IP Multimedia Subsystem (IMS) standard. However IMS requires that each mobile device have a unique IP address, which is a persistent IP address in order to ensure full bi-directional services.
IPv6 through its large address space ensures that each mobile device can have its own unique IP address. Further, Mobile IPv6 makes use of the extension headers to add powerful capabilities such as route optimizations between mobile nodes, when roaming between different 3G networks.