Hi, In ns, the command duplex-link-op can be used to specify the orientation of a duplex-link. Now, I want to know how to specify the orention of a simplex-link. There is no command such as simplex-link-op. Could anyone tell me something about it? I also want to know where the command "duplex-link-op" is defined. Thanks in advance. Best regards, Huang mailto:thumahh@263.net