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set stoptime 200.0 ; # simulation end time (seconds)
set owdelay 1000ms ; # 1-way delay
#set myaddr "10.11.12.13"
set myaddr "128.32.130.59"
set ns [new Simulator] ; # create simulator object
$ns use-scheduler RealTime ; # specify the real-time sync'd scheduler
set bpf [new Network/Pcap/Live]; # live traffic -- read IP pkts
$bpf set promisc_ true ; # use promiscuous mode
$bpf open readonly fxp0 ; # specify interface
set ipnet [new Network/IP] ; # live traffic -- write IP pkts
$ipnet open writeonly
$bpf filter "icmp and dst $myaddr"; # only ICMP packets for me
set pfa [new Agent/Tap]
set ipa [new Agent/Tap]
set echoagent [new Agent/PingResponder]
$pfa network $bpf ; # associate pf net object w/tap agent
$ipa network $ipnet ; # associate ip net object w/tap agent
# create topology in simulator
set node0 [$ns node]
set node1 [$ns node]
set node2 [$ns node]
$ns simplex-link $node0 $node2 100Mb $owdelay DropTail
$ns simplex-link $node2 $node1 100Mb $owdelay DropTail
# place agents in topology
$ns attach-agent $node0 $pfa; # packet filter agent
$ns attach-agent $node1 $ipa; # ip agent (for sending)
$ns attach-agent $node2 $echoagent
$ns simplex-connect $pfa $echoagent
$ns simplex-connect $echoagent $ipa
puts "listening for pings on addr $myaddr..."
$ns run ; # start emulation
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