IPv6 Network Administration

Introduction to Mobile IPv6

In these days of cellphones and wireless networking of all kinds, mobility for equipment now carries the expectation that you can take your laptop and use it for email, web, and so on more or less anywhere. By default, full mobility is not catered for—in other words, you cannot be on a wireless LAN in one office, put a machine to sleep, take it to another office, and wake it, and expect all existing connections to be preserved and everything to "just work." Furthermore, there are roaming issues with multiple points of access to a given network, address assignment issues and so on. The mobility problems that Mobile IPv6 attempts to solve are a very well-defined subset of these, and have to do specifically with your layer 3 point of attachment to the network, and hence to your address, routing table, and other network infrastructure resources.

So how do we solve the problem of using a laptop in another person's network but still being able to get to your usual, within-home-network resources, as well as maintaining existing connections? The usual mechanisms invoked by the IPv6 stack on a link change, like stateless autoconfiguration, effectively kill existing TCP connections because TCP connections have a fixed address at either end of the connection. Furthermore, RAs in managed networks will have the same effect, and it would be inappropriate to suppress these mechanisms simply for this purpose.

The approach that Mobile IPv6 takes is as follows. Nodes