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Failed Route Discovery....

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• Failed Route Discovery operations
  • A route discovery message can fail to arrive at the destination node:

    because the destination node has moved out of range !!!

    Example:

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  • Result:

    The ROUTE REQUEST message will be transmitted (broadcast !) in vain !!!

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• Consequence of failed route request operations
  • Consequences of a failed route request operation:

    We (may) need to retry the route discover operation It is possible that the route discovery failed due to transmission errors However: Each ROUTE REQUEST messages will use a lot of bandwidth because Nodes must broadcast the ROUTE REQUEST message to their neighbors !!!

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  • Therefore:

    We should retry a failed route discovery But: We cannot perform the route discovery: for too long,        nor       for too often

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• Limiting the duration of a route discovery operation
  • Recall:

    A route discovery is performed only when a node: has a message to transmit the destination does not have a source route to the destination

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  • Limiting the duration that a node will perform route discovery (for the same destination):

    A message is inserted into a send buffer Each message is stamped with: the time that the message was placed in the send buffer When the time exceeds a threshold: The message is deleted from the send buffer

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• Limiting the frequency of a route discovery operation
  • Limiting the frequency that a node will perform route discovery (for the same destination):

    Exponential backoff....