[ns] How to make simplex-link down ?

[G.Chandramowli]

Hi everybody , 
   I am trying to  make a simplex-link down .
   I tried the same as what the duplex link does but it ends up in error.
   Anybody has any idea to know what has to be done extra to make a simplex-link
down..?

   Thanks in advance .
   Mouli.