[ns] please help me about this error

[ma-haiyuan]

I'm a newer of NS.
I'm making simulations on Multicast. The error message is as follows:


(_o3 cmd line 1)

    invoked from within

"_o3 cmd queue-parameter _o17 _o24 2 6"

    invoked from within

"catch "$self cmd $args" ret"

    invoked from within

"if [catch "$self cmd $args" ret] {

set cls [$self info class]

global errorInfo

set savedInfo $errorInfo

error "error when calling class $cls: $args" $..."

    (procedure "_o3" line 2)

    (SplitObject unknown line 2)

    invoked from within

"$ns queue-parameter $n3 $n4 2 6"

    (file "1.tcl" line 88)





Please help me. What's the reason of this error , and how can I correct it? 
Please help me.

Thank you very!