Figure 14-3 shows the small MIPv6 testbed used for performing the handover tests. A MN running MIPL v1.1 is away from home (the HA also running MIPL v1.1) and can attach to one of two networks represented by the SSIDs ‘roam1’ and ‘roam2’. We decided to conduct handover tests from one foreign network to another (e.g. rather than from home network to foreign network) as the nature of mobility implies that when one is mobile, one is very rarely located at the home network.

Handovers from one network to another were forced by turning off one of the APs so that the MN would immediately associate with the other AP and thus receive different RAs than on the previously connected network.

The handover times were measured from the point at which the AP is switched off (link down notification) to when the Binding Acknowledgement is received from the Correspondent Node with each event being timestamped in the relative logs. Note that the Return Routability protocol was enabled for Route Optimisation.

Reducing the Router Advertisement Intervals

In order to demonstrate the effects of reducing the RA interval we performed handover tests with various configurations of RA intervals on the Cisco 2611 access routers. As described earlier, upon detecting movement, the MN will issue a RS assuming it hasn’t received a new RA already. As can be seen from Figure 14-4, the time it takes for the MN to receive a solicited RA is fairly random within a given (configurable) time window.