Analysis and Design of a Modern SCADA System

to initiating route discovery [ 59 ]. This may not be acceptable in situations
where the mobility rate is high, and during busy connections established
over a short period of time which increases message overheads due to low
maintenance capability [ 63 ]. Aggressive flooding is problematic in DSR
and is an important factor to consider since it decreases the ability to
maintain overheads in mobility situations. Furthermore, a larger header is
required to store information in large networks, thus the using extra
bandwidth and processing power for its computation [ 63 ]. From the
previous discussion, DSR protocol works in good manner in small to
medium size networks. The algorithm in Figure 2. 13 shows how DSR
enables communication between two nodes.
If a node has a packet to send, the algorithm checks for a valid
route to the destination in its route cache. If the route is not available a
route request is initiated and broadcast over the network. However, if the
route to the destination is available in route cache, it is then established and
the node sends a packet to the receiving node. If the receiving node is
ready, transmission begins and terminates if transmission is successful. If a
failure occurs, a route RERR is sent that triggers route maintenance which
enables the source node to look for possible alternative routes [ 55 ].