Mobile ad hoc networks (MANET)

Principle
Reactive routing protocols
A node only knows the routes it actually requires
No periodic updates
Tasks of a reactive routing protocol
Finding a route (Route Discovery)
Only when a node wants so send data to a node, but does not yet have a route to that
node
Maintaining a Route (Route Maintenance)
Only active routes are maintained
Comparison to proactive routing protocols
Advantage
Only routes that are actually needed are determined and maintained
No periodic transmission of messages necessary less use of resources
Disadvantage
Time delay at the beginning of a communication: route has to be determined first
Control overhead depends on number of connections and mobility
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Route Discovery
Example: Ad Hoc On Demand Distance Vector Routing (AODV)
Sender S floods the ad-hoc network with a Route Request (RREQ)
RREQ contains source address S and destination address D
Nodes that are involved in forwarding the RREQs store the address of
the node from which they received the RREQ
The so-called „Reverse Path“ into the direction of the sender S is built
up
Only works with bidirectional links!
When the destination node D receives the RREQ, it answers with a
Route Reply (RREP)
RREP contains source address S
RREP is forwarded via unicast to node S (use of Reverse Path)
With the forwarding of the RREPs, the so-called “Forward Path” into the
direction of the destination node D is built up
The Forward Path is used for data traffic
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