[ns] How to generate a Tracefile for the Application/Traffic/Trace input

[Mayur]

Dear NS-Lovers,

How to generate a "_*binary format file*_" (with two columns, 
<time_in_us, pkt_size> ) as expected by the *Application/Traffic/Trace*? 
Any readymade utility code? I don't understand the exact format, that is 
expected here. And hence how to generate it....

I tried on the net, but could not find. Perhaps the question is too 
trivial...

Mayur