How to set the ns-tcl-lib path?

["HUANG PENG" <huangpeng_buaa@a-1.net.cn>]

 Hi, everyone:
 
 Would you mind sharing your experience with me: How did you set the path environment variable to inform the ns where

 the ns-tcl-library resides. 
 
 When I run ns like that:

 >ns
 %
 %source ./topo-view.tcl
 %view-topology ts100.tcl out.nam 0

 the system tells that:

 creating links O.._04: unable to dispatch method duplex_link_of_interface

 I judge it to be the problem of setting the lib path, isn't it?

 regards

 Huang Peng