A conversation about inter-arrival time, or reason #3,781 why I hate ns-2

This is a rephrase of an e-mail conversation over two days with the very smart post-doc that used to work with my research group.

Me: I am having some trouble with ns-2.

Pd: What's that?

Me: Well, I'm noticing a difference between utilization at 99% load and 130% load.

Pd: Why are you measuring at 130% load?

Me: Originally, it was out of curiousity. Now, it's because I'm seeing this disparity.

Pd: How are you defining load? Input rate over link capacity?

Me: Yeah, I'm calculating the packet inter-arrival rate for the desired load, and setting the constant bit rate traffic generator accordingly.

Pd: Oh, you should measure it. You can't trust that just because you set the inter-arrival rate on the CBR in ns-2, it will be reflected correctly.

Me: Oh. Hm. Oh.

Two hours later, a month-long problem is solved. Just six more things on my "to-do" list before I have my final journal paper submission draft. This weekend will be busy.