is because there is no information mentioned about this protocol regarding the multicast
tree construction also there are no details about the messages format and role for joining/
leaving the multicast tree. For the previous reasons, the implementation of EM2NET will
not give the real behaviour of the protocol.
In the investigated scenario, SARM, E2M and DDM run over the MANET unicast
routing protocol AODV (Ad Hoc On-Demand Distance Vector) [16]. NS-2 simulator
already provides the AODV routing agent implementation, while a modification for
AODV agent is done in order to make AODV agent able to exchange routing information
with the Xcast agent. To facilitate the interaction between the Xcast agent and the AODV
agent, cross-layer design approach has been adopted, wherein an Xcast agent can access
the AODV routing table to group the nodes which are reachable through the same next
hop. In case a route is not available, the Xcast agent simply sends a unicast packet to the
AODV agent, which triggers a route request for this destination. When the AODV agent
receives a route reply from the required destination, it updates its route table accordingly.
An Xcast agent can now directly obtain the next hop information from the routing layer.
Table 5.1 outlines some of the AODV parameters selected for our simulation work. The
performance metrics considered in this proposed work are extra packet header size,
packet delivery ratio and end to end delay. These metrics used to investigate the
scalability and the efficiency of the proposed protocol.
5.7.2 Results and discussion
This section will discuss the results obtained from the simulations; these results will be
organized according to the metrics used in the evaluation. For each value obtained, the
simulation has run for 10 times and the average of the output values taken. Also an error
rate is calculated which equals the standard deviation for the 10 output values. For each
evaluation metric, the simulation is divided into two groups. In the first group of
simulation, the group size is fixed to 30 nodes and the pause time value is varied, whereas
in the second group the multicast group size is varied with fixed pause time value to 0s.
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