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It is a source initiated routing
protocol in mobile adhoc networks.
The algorithm consist of 2 phases
1. Route discovery phase
2. Route maintenance phase
In route discovery phase the path
from source to destination is identified by broadcasting route request packet
[RREQ]. When the intermediate node receive RREQ they will create a backward
pointer and continue the broadcast when the route request packet reaches the destination
a route reply would be generated [RREP]. The route reply will have information about
the path that can be chosen for the packet transmission.
The route request packet can have
following information.
1. Source id
2. Destination id
3. Sequence number
4. Backward pointer information
5. CRC and
6. Time to live[TTL]
In the above network the RREQ
will be broadcasted by the source node 1 to its neighbor and neighbors will
check whether RREQ is already processed. If it is already processed the packet
will be discarded.
If it is not processed a backward
pointer is created and the broad cast continues.
When the packet is reached at
destination a route reply is created [RREP] in the above network the first RREP
is sent to the source can have the path information as 1-2-4-6-8.
When the source receives this
information it will be stored in the routing table. Mean while the destination
can create one more RREP which can have the information as 1-3-7-8 the
destination will send this RREP to the source and will also ask the source to
discard old path as the new path is having minimum number of hops.
Route
maintainence phase
The nodes in the network
periodically exchange hello messages to inform that they
are still a part of network and
the path is valid. Whenever there is a link failure detected. A route error
packet [RERR] will be sent to the source indicating the path is no more valid.
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