Mobile IPv4 based deployed infrastructures cannot get converted into fully functional Mobile IPv6 infrastructure overnight. There must be a complete mechanism for transition. Networks should first incorporate IPv6 complaint nodes and give communication capability between IPv4 and IPv6 nodes. The following points will try to put light on; what changes can be made step by step to convert an IPv4 infrastructure to IPv6 infrastructure.

To identify one network is different from other network, IPv4 and IPv6 both use Network Access Identifiers. Identification of Mobile Node with its Network Access Identifier allows its integration in IPv6 AAA infrastructure.

As we know, most of the Mobile IPv4 deployments already use Network Access Identifier, so, it sets precedent for Mobile IPv6. Thus first the network administrator of a Mobile IPv4 infrastructure can put an AAA server in its network. So, Mobile Nodes can start AAA authentication infrastructure despite of using IPv4 addressing.

This is a suggested first step of transitioning to Mobile IPv6. Mobile IPv6 uses the AAA server facility to auto-configure its Mobile Nodes on boot time. This gives administrators an easy configuration of nodes. As mentioned in last topic, that AAA infrastructure can be introduced in IPv4 network because IPv4 network supports Network Access Identifier. So, after introduction of AAA server in the network the nodes can also be changed to get all the configuration parameters from AAA server during bootstrap.

Hierarchical Mobile IPv6 is used to lessen down the routing update change at Home Agent when a Mobile Node is moved from one subnet to other subnet of the same network.

This same mechanism can be provided in IPv4 network. It will help a lot in transition to IPv6 Mobile IP network. A Mobility Anchor Point (MAP) can be provided at the point where all subnets get connected. This MAP will act as a Foreign Agent in Mobile IPv4 network until the network is completely upgraded to Mobile IPv6 network.

The IETF group working on CDMA2000 architecture is moving in the same direction as mentioned in last three points. They have introduced an AAA server in their network while the network is still working on IPv4.

AAA Server dynamically generates the key upon the request of Mobile Node. AAA Server delivers this key to Home Agent, so that the Home Agent can use this key to encrypt the messages between itself and Mobile Node. This method is same as AAA infrastructure of IPv6 and provides a gateway to the transition to IPv6.

CDMA2000 has also put bootstrap capability in its nodes. CDMA2000 have PDSN that participates in bootstrap scheme.

So, like this CDMA2000 have tried to make a transition towards Mobile IPv6. They are bootstrapping for easy auto-configuration. They are dynamically assigning Home Agent Address and they are generating authentication key through their own AAA mechanism. CDMA2000 is the best example of Mobile IPv4 to Mobile IPv6 transition.

The discussion cannot be completed if we do not discuss the changes induced in OSI model due to Mobile IPv4 transition to Mobile IPv6. This section will discuss layer by layer till hardware layer, whether a change will occur or not.

Transport Layer is very important in communication because it maintains family TCP and UDP connections. TCP uses IP Addresses and Port numbers to identify its connections. When a network is updated to IPv6, TCP connections will be recognized by an IPv6 address and port number. So, the basic phenomenon is same. Only addressing will be changed. The change of IP Address scheme will give more options and services at Network Layer. So Transport Layer can get use of advanced options supplied by IPv6.

Obviously, IPv6 will bring a great change in this layer. All the addressing scheme will be changed. Procedures for network prefix detection and location update signaling will be changed. In Mobile IPv4 transport layer used to send control messages in a UDP packet but now IPv6 has inherent support for Mobile IP. So, control messages are sent by Network Layer. ICMPv6 is used instead of ICMPv4.

Data Link Layer also needs not to get changed for IPv6. Only the point is that ARP protocols will start converting IPv6 address to MAC, instead of doing IPv4 to MAC address conversion. Other changes of Data Link Layer protocols are already discussed in detail.

Theoretically there will be no change in physical layer as far as the connectors and physical ports are concerned. Due to additional IPv6 fields and longer addresses routers may need large buffers and faster processing speeds but the basic mechanism remains the same. Foreign Agents are removed completely. MAP devices are added for fast routing updates at Home Agent etc.

Special routers like MAP router, requires few hardware changes. Nodes must be IPv6 capable so that they may read routing header properly.