Gugrajah_Yuvaan_ Ramesh_2003.pdf

Simulation ofa Load Balancing Routing Protocol Chapter 3
The type of information appended depends on the DLAR scheme that is
implemented. The destination accepts multiple route requests within an appropriate
time frame, reply_delay, after receiving the first route request. This allows the
destination to determine which routes are available and the quality of the available
routes. The destination chooses the most suitable route and transmits a route reply
packet using this route to the source. Once the source receives the route reply, it can
begin transmitting the data on the selected route.
While the route is being used, intermediate nodes piggyback load information on the
data packets. The destination node uses this information to monitor the status of the
route to determine if the route is becoming too congested. The destination can decide
to find a new route before the current route fails and broadcasts a route request in the
same way that the source initiates a route request procedure. The route request is
eventually propagated to the source, which can analyse the load information attached
to the route request by intermediate nodes and send the next packet on the most
suitable route. In this way routes are dynamically selected during a session in order
to perform load balancing and reduce congestion in the network.
Unlike AODV and DSR, DLAR does not allow intermediate nodes to respond to
route requests. Only the destination node is allowed to respond to route requests,
which prevents stale route information from the caches of intermediate node being
used. Preventing intermediate nodes from generating route replies also prevents a
flood of route replies from multiple intermediate nodes with cached information and
reduces the congestion caused by the reply storm.
Figure 3-2 demonstrates the congestion that is created when intermediate nodes are
allowed to respond to route requests with route replies, hence neglecting the potential
congestion that can result. Assume that node 2 initiates a route request for a route to
node 7 and obtains the route {2, 4, 5, 6, 7}. When node 3 requests a route to node 7,
node 4 responds with a cached route resulting in node 3 using the route {3, 4, 5, 6,
7}. This new route overlaps the previous route and the same process occurs when
node 1 requests a route to node 6. Node 1 receives the route reply from node 4
indicating that {I, 8,4,5, 6} is a suitable route. It can be seen that although allowing
3-4