Re: link dynamics bug

[Hyogon Kim <hkim@bellcore.com>]

I have another question on link dynamics modeling. It seems to
me that an existing TCP connection just hangs when the link it
traverses goes down and up in NS2-1b2. However short the link 
failure is, the TCP just stops there. I've tried to create an
alternate route and see if Session routing can reroute the 
affected TCP connection, but it didn't work either. Am I missing
something here? I am attaching my script file below, and the
two tcpDump traces with and without the failure. 

Please help!

- Hyogon

---------------------------- script --------------------------

set ns [new Simulator]

proc tcpDump { tcpSrc sample_interval } {
    global ns
    proc dump { src sample_interval } {
        global ns
        $ns at [expr [$ns now] + $sample_interval] "dump $src
$sample_interval"
        puts [$ns now]/cwnd=[$src set cwnd_]/ssthresh=[$src set
ssthresh_]/ack=[
 $src set ack_]
    }
    $ns at 0.1 "dump $tcpSrc $sample_interval"
}


set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]

$ns duplex-link $n0 $n1 1.5Mb 10ms DropTail
$ns duplex-link $n0 $n2 1.5Mb 10ms DropTail
$ns duplex-link $n2 $n1 1.5Mb 10ms DropTail

set tcp1 [new Agent/TCP]
$ns attach-agent $n0 $tcp1
set sink1 [new Agent/TCPSink]
$ns attach-agent $n1 $sink1
$ns connect $tcp1 $sink1
set ftp1 [new Source/FTP]
$ftp1 set agent_ $tcp1

$ns rtmodel Deterministic {} $n0
    $ns rtproto Session


$ns at 1.0 "$ftp1 start"
$ns at 8.0 "exit 0"
tcpDump $tcp1 1

$ns run

------ output with "$ns rtmodel Deterinistic {} $n0" line above ------
0.10000000000000001/cwnd=1.000000/ssthresh=110/ack=-1
1.1000000000000001/cwnd=8.000000/ssthresh=110/ack=6
2.1000000000000001/cwnd=15.000000/ssthresh=53/ack=133
3.1000000000000001/cwnd=1.000000/ssthresh=26/ack=209
4.0999999999999996/cwnd=1.000000/ssthresh=2/ack=209
5.0999999999999996/cwnd=1.000000/ssthresh=2/ack=209
6.0999999999999996/cwnd=1.000000/ssthresh=2/ack=209
7.0999999999999996/cwnd=1.000000/ssthresh=2/ack=209


------ output without "$ns rtmodel Deterinistic {} $n0" line above ------
0.10000000000000001/cwnd=1.000000/ssthresh=110/ack=-1
1.1000000000000001/cwnd=8.000000/ssthresh=110/ack=6
2.1000000000000001/cwnd=15.000000/ssthresh=53/ack=133
3.1000000000000001/cwnd=4.000000/ssthresh=26/ack=316
4.0999999999999996/cwnd=31.657495/ssthresh=26/ack=501
5.0999999999999996/cwnd=37.099268/ssthresh=26/ack=688
6.0999999999999996/cwnd=41.862591/ssthresh=26/ack=876
7.0999999999999996/cwnd=46.114784/ssthresh=26/ack=1063










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Hyogon Kim (hkim@bellcore.com)	       		       |        (201) 829-4728
Research Scientist				       |           MCC 1G-231B
Internet Architecture Research Laboratory	       |      445 South Street 
Bell Communications Research			       |  Morristown, NJ 07960
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