In ad hoc networks, it is sometimes desirable to transmit packets of a single message using multiple paths using an 802.11 protocol.
(a) Can you think of any specific reasons for this?
(b) If you need to employ two alternate paths, how would you determine that
in Problem P13.7 using DSR?
(a) For wireless ad hoc networks, the most natural way of finding a path is
broadcasting since radios are based on omni-directional antennas. However,
sometimes node or link failure could happen and, by using alternate paths, data
can be easily rerouted. When a node cannot forward a packet due to a broken
link, it will send a route error packet (RERR) to the source. The source can then
initiate a new route discovery to find a new route to the destination. Network
reliability is most crucial for performance critical networks; route diversity
offers redundancy via alternate paths.
(b) If we need to employ alternate paths, for Problem 13.7, such as DSR, when a
node gets a packet that it needs to send on a particular link, If it knows that the
link is down, it looks up the cache and sends on an alternate route; but doesn’t
start a new round of route discovery.
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