MIP, for handoff to take place, the mobile node must first detect the new IP sub network, select it and initiate handoff. The delays involved include the time for the mobile node to initial router solicitation and router advertisement messages (2ts). The next delays are the time for the mobile node to register with the NFA (2th), cache the message from the home agent (2th - ts). During the message caching process two signaling flows take place: route optimisation and smooth handoff. As the NFA caches the registration message, it sends a binding update message to the OFA. The OFA upon receiving the binding update message (tno) starts sending packets destined to the MN to the NFA (ts + tno) thus starting the interdomain handoff. This result to the total time for starting the interdomain handoff or smooth handoff is: hMIP_smh (2ts s + (2th - ts) + tno + (ts + tno)) = 2ts + 2th + 2tno (22.12) During the route optimization, other delays are involved in the handoff pro- cess including the time when the OFA updates its binding cache with the care of address (CoA) of the mobile node (th - ts)) and sends a binding warn- ing message to the HA of the mobile node. The HA then sends the binding update message to the correspondent node (thc). Lastly, the correspondent node will then send the packets for the mobile node to the NFA which are then subsequently delivered to the mobile node with time (tmc). The total time for route optimization is: hMIP_ropt = (2ts + (2th - ts) + tno + (th tmc) = 3th + t no t ha t tmc (22.13) After route optimization, handoff is triggered. It is essential to understand the two signaling flows involved in route optimization in terms of the time packets from the correspondent node reaching the mobile node and the time the packets forwarded by the OFA reach the mobile node as well. There is a blackout period until packets from the OFA arrive at the mobile node. This blackout period is about 2ts + 2th + 2tno after which the VoIP communication resumes with a disruption until packets from the CN reach th