Meghadoot

- A Hybrid Wireless architecture

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Route Discovery

INs are the core to the route discovery process. In the control zone, if a route is required to a destination, the route cache (it is a two-level cache explained in Section 3.6) is first checked. A route cache is used in order to reduce the time taken to setup the path. If no route to the destination is present in the route cache, the route request is sent to the associated IN through the next hop to that IN. The intermediate nodes merely forward the route request to the next hop for the IN to which the route request is to be sent. Route requests are handled at the IN depending on the type of the destination, where type can be one of the following:

• HOME NODE: If the MN is in the CZ of its HA.
• OUTSIDE NODE: It means that the present IN is the MN's HA, but the MN is currently registered with another IN as a foreign node.
• FOREIGN NODE: The MN is registered with this IN as a foreign node.
• REALLY OUTSIDE NODE: The node is either in a different Meghadoot network or is an Internet address.

The handling of route requests is as follows:

• Destination type is HOME NODE: Since the IN maintains complete topology information of its CZ, it can compute a route from the requesting MN to the destination and send the route back. If the IN does not have any information about the destination, which is supposed to be in its control zone, an error is sent back.
• All Other Cases: For any other type of destination, the IN sends a route reply with a route through the IN, with the last hop as the actual destination and the penultimate hop as the IN. When the actual data packet is received at the IN, it is handled appropriately as explained in Section 3.4