A snapshot of an ad hoc network is shown in Figure 13.19.

Question

Describe briefly the process taken to do the following:

(a) You need to create a route from the source node 6 to the destination node 23 using the DSR algorithm.

(b) Repeat part (a) using TORA routing.

(c) What changes would you make in part (a) if you use the AODV protocol?

Answer 1

(a) By using DSR algorithm to create a route from 6 to 23, node 6 at first checks
its route cache to determine whether it already has a route to the destination 23, if it has, it will use this route. If it does not have such a route, it initiates route
discovery by broadcasting a route request packet. This route request contains the
address of node 23. A reply is generated when the route request reaches either
node 23, or an intermediate node whose route cache contains an unexpired route
to the destination.
(b) For TORA, when node 6 needs a route to node 23, node 6 broadcasts a query
packet containing the address of node 23. This packet propagates through network until it reaches either node 23, or a node having a route to the node 23. The recipient of the query then broadcasts an update packet listing its height with respect to node 23.when this packet propagates through the network; each node that receives the update sets its height to a value greater than the height of the neighbor from which the update message has been received.
(c) For AODV, node 6 broadcasts a route request packet (RREQ) to its neighbors,
which then forwards the request to their neighbors, and so on, until either node 23 or a node with “fresh enough” route to node 23 is located. The main difference
between the DSR and AODV is that DSR uses source routing and AODV uses
forwarding tables at each node. During the process of forwarding the RREQ,
nodes record in their route tables the address of the neighbor from which the first
copy of the broadcast packet is received, thereby establishing a reverse path.