re, triangle routing leads to potential problems in long latency and high resource usage for routing of incoming packets to the MN. These prob- lems are solved in [10], which allows the CN to cache the binding of the MN and directly tunnel packets to the MN using the MN's current CoA. The CNs cache is updated by the HA whenever the HA receives an updated registration from the MN. Note that due to security considerations, the CN only trusts the notification messages sent by the HA, which has an authenticated fixed IP address. Another problem is that a handoff from one FA to another is not seamless, as the MN is unable to receive any packets until the handoff completes a successful registration of the new CoA at the new FA. Packets forwarded to the MN via the FA during this period are either lost or deferred. To address this problem, authors of [10] also propose to set up temporary con- nections between the FAs of the previous network (oFA) and the new network (nFA). Once an MN registers in the new network, it will tell its new CoA to the oFA before sending out the registration message, and the oFA will for- ward all incoming packets to the nFA until the handoff is completed. Since the oFA is usually closer to nFA than the HA and CN, the packet delivery inter- ruption period will be greatly shortened. To further shorten the interruption period, [11] also proposes to predict potential handoffs by tracking the MN's locations. Whenever the MN is going to move out of the coverage area of the WLAN it is currently associated with, it will initiate the handoff in advance SO that the handoff completes before the WLAN signals become undetectable. In MIP, an MN should register to the HA every time its CoA is changed. If the MN moves frequently between different subnets of a foreign network, it will send registration messages frequently back to the HA, which will gen- erate heavy signalling traffic and cause long handoff delays if the HA is far away from the MN. A number of schemes have been proposed to manage such "intra-dom