DHCP Servers

Initially the DHCP servers were intended to be part of the solution. The idea was to use
the DHCP server as initiator of the updates. Since this would require control over the
DHCP server, the mobility would be limited to networks under the direct control of
the solution. As the design goal was to allow mobility over the entire Internet, this
solution was abandoned about halfway through the project. However, the DHCP
servers were kept for testing purposes throughout the project.

The DHCP servers were configured as a master and a slave server. If the slave has not
gotten any signal from the master for more than 30 seconds, it assumes the master has
failed and the slave takes over. This setup ensures that if only one server fails the
clients can still get a valid IP address in a network known to the routers. The master
and slave splits the addresses of the different subnets between them to avoid address
collisions. If one server goes down, the other server takes over the responsibilities
for the other server’s addresses. This operation is reversed when the faulty server
comes online again.