Hope you are familiar with the term routing. We need to find a path from a source to the destination in the network to forward the packets. Finding the best possible path is often a matter of question here. We need to find a path with minimum packet loss, energy requirements and other costs.
Apart from the customary routing techniques, the MANET routing techniques are different as each individual node can act as a router and host. Thus the level of security is compromised for MANETs.
Routing Protocols in MANETs
In MANETs, the routing protocols can be categorized as:
- Table-driven (Proactive)
- On-demand (Reactive)
Table-driven protocols include DSDV (destination sequenced distance vector) and OLSR protocol whereas AODV and DSR are the examples of On-demand routing protocols.
- Routing information is stored in the roting table and occasionally altered when there is topology change.
- This protocol is not preferred for networks with large number of nodes as it is difficult to maintain routing information of each node in each node’s routing table.
Table-driven routing protocols maintain a routing table and find the route in advance. It exchanges routing information occasionally to preserve the route.
But reactive routing protocols find a route only when it is required. Whenever there is a path failure, an optional route is chosen.
Let us consider the case of a reactive routing protocol (AODV) and check the possible route of a route reply packet (RREP) from a destination to a source. Here the node A need to set up a route to node J.
- To establish the route, A needs to broadcast RREQ packet to all the other neighboring nodes in the network.
- When node J receives the RREQ packet, it sends back a RREP packet.
- This packet is unicasted to the sender node (ie A) through the other neighboring nodes.
For more information on MANET, read on MANET characteristics.