sir, When i am running below tcl script it gives error:"Flow 1 starts at time 0.000000
Segmentation fault (core dumped)" but in other tcl script is work better than below tcl script....................................... I am not understand what error in below tcl script when nam is work properly. -----------------------------------mkc-T2.tcl------------------------------------------------------------------------------------ # create scheduler set ns [new Simulator] set f [open out3.tr w] $ns trace-all $f set nf [open out3.nam w] $ns namtrace-all $nf # create topology # set number of flows set N 4 # set the output file for {set i 1} {$i<=$N} {incr i} { set out_($i) [open out$i.txt w] } # set the physical source and sink for {set i 1} {$i <= $N} {incr i} { set R_($i) [$ns node] } $ns duplex-link $R_(1) $R_(2) 20Mb 10ms MKCQueue set mkcq_(1) [[$ns link $R_(1) $R_(2)] queue] $mkcq_(1) set C 20000000 $mkcq_(1) set T 0.1 $mkcq_(1) set rid 1 $ns duplex-link $R_(2) $R_(4) 10Mb 1000ms MKCQueue set mkcq_(2) [[$ns link $R_(2) $R_(4)] queue] $mkcq_(2) set C 17000000 $mkcq_(2) set T 0.1 $mkcq_(2) set rid 2 $ns duplex-link $R_(4) $R_(3) 20Mb 10ms MKCQueue set mkcq_(4) [[$ns link $R_(4) $R_(3)] queue] $mkcq_(4) set C 20000000 $mkcq_(4) set T 0.1 $mkcq_(4) set rid 3 $ns duplex-link $R_(3) $R_(1) 10Mb 1000ms MKCQueue set mkcq_(3) [[$ns link $R_(3) $R_(1)] queue] $mkcq_(3) set C 17000000 $mkcq_(3) set T 0.1 $mkcq_(3) set rid 4 #create and attach BWCSink agents set Snk_(2) [new Agent/MKCSink] $Snk_(2) set packetSize_ 40 $ns attach-agent $R_(2) $Snk_(2) set Snk_(1) [new Agent/MKCSink] $Snk_(1) set packetSize_ 40 $ns attach-agent $R_(4) $Snk_(1) set Snk_(4) [new Agent/MKCSink] $Snk_(4) set packetSize_ 40 $ns attach-agent $R_(3) $Snk_(4) set Snk_(3) [new Agent/MKCSink] $Snk_(3) set packetSize_ 40 $ns attach-agent $R_(1) $Snk_(3) set Src_(2) [new Agent/MKC] $ns attach-agent $R_(1) $Src_(2) $Src_(2) set alpha_ 200000 $Src_(2) set beta_ 0.5 $Src_(2) set packetSize_ 200 $Src_(2) set init_rate_ 100000 $Src_(2) set fid_ 2 set Src_(1) [new Agent/MKC] $ns attach-agent $R_(1) $Src_(1) $Src_(1) set alpha_ 200000 $Src_(1) set beta_ 0.5 $Src_(1) set packetSize_ 200 $Src_(1) set init_rate_ 100000 $Src_(1) set fid_ 1 set Src_(4) [new Agent/MKC] $ns attach-agent $R_(4) $Src_(4) $Src_(4) set alpha_ 200000 $Src_(4) set beta_ 0.5 $Src_(4) set packetSize_ 200 $Src_(4) set init_rate_ 100000 $Src_(4) set fid_ 4 set Src_(3) [new Agent/MKC] $ns attach-agent $R_(4) $Src_(3) $Src_(3) set alpha_ 200000 $Src_(3) set beta_ 0.5 $Src_(3) set packetSize_ 200 $Src_(3) set init_rate_ 100000 $Src_(3) set fid_ 3 # connect each pair of sender and receiver for {set i 1} {$i<=$N} {incr i} { $ns connect $Src_($i) $Snk_($i) } $ns cost $R_(4) $R_(3) 1 $ns cost $R_(4) $R_(2) 10 $ns compute-routes set routelogic [$ns get-routelogic] # schedule the events set starttime_(1) 0 set starttime_(2) 30 set starttime_(3) 60 set starttime_(4) 90 $ns at 0 "$Src_(1) start" $ns at 30 "$Src_(2) start" $ns at 60 "$Src_(3) start" $ns at 90 "$Src_(4) start" for {set i 1} {$i<=$N} {incr i} { $ns at $starttime_($i) "record $Src_($i) $out_($i)" } set tfinish 500 for {set i 1} {$i<=$N} {incr i} { $ns at $tfinish "$Src_($i) stop" } $ns at $tfinish "finish" proc record {bwcsrc file} { global ns f nf set step 0.1 set now [$ns now] set rate_ [$bwcsrc set rate_] set pkt_loss_ [$bwcsrc set pkt_loss_] puts $file "$now $rate_ $pkt_loss_" $ns at [expr $now+$step] "record $bwcsrc $file" } proc finish {} { global ns f nf $ns flush-trace close $f close $nf puts "running nam...." exec nam out3.nam & exit 0 } $ns run plz anybody check above tcl script and find out where is the error.....and how to solve this error. thank you