[ns] Getting different throughput with different CBR interval?

Does anyone know why I am getting different throughput when I set the CBR interval to different values? For example, if I set $cbr set interval_ 0.001 $cbr set interval_ 0.01 $cbr set interval_ 0.1 I get different throughputs. Anyone has an idea why?

[ns] Backoff values in a trace file?

Is the backoff value a node chooses recorded in the trace file? If not, is there any way I could obtain all the backoff values chosen by one (or all) nodes?? Thanks

[ns] Getting the same trace file over and over?

Hi, I have very simple scenario, 5 nodes sending CBR traffic to a sink (I am only looikng at MAC layer). Every time I run the tcl file, I get the exact same trace file. However, this should not be the case since 802.11 chooses random backoff value, and, therefore, the trace should be differnt at