[ns] packet transmission

[Daria Stepanova]

Hello Ns-users,
Maybe somebody could help me.
I am doing simulation with aodv and dsr routing protocols
and now I have two questions:
- first, how to manage to avoid calculating same packet transmission 
multiple times;
- and second, if two or more packets are transmitted simultaneously, 
how to make both of them are corrupted and removed.
Even if you don't know answers I will be thank you for any clue.
Thank you in advance,
Daria