[ns] why i can't use commands to control the layout?

[min xie <xie_min_sg@yahoo.com>]

Hi, all

I tried to use the command like

$ns duplex-link-op $n0 $n1 orient right-down

to control the layout.  However, after i put these
commands, the topology figure disappeares from the NAM
screen. Why? 

Thanks

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