1. Create two ping agents and attach them to the nodes between which the Round Trip Time is to be calculated.
set p0 [new Agent/Ping]
$ns attach-agent $n0 $p0
set p1 [new Agent/Ping]
$ns attach-agent $n2 $p1
#Connect the two agents
$ns connect $p0 $p1
2. When ping packet is received the recv{} procedure is called
Agent/Ping instproc recv {from rtt} {
$self instvar node_
puts "node [$node_ id] received ping answer from \
$from with round-trip-time $rtt ms."
}
The member variable 'node_' of the base class 'Agent' is used to get the node id for the node to which the agent is attached and the variable rtt gives the Round Trip Time.
