add per-link events.
Add a new flag (-E) to turn on the per-link event. This implies the event-driven mode (-e).Each peer i sends an offer to its neighbor j every offer_interval times probability of j seconds, deterministically.
add auto convergence feature
this feature allow the specification a parameter of convergence on the average receiving delay and the termination of the simulation
add peer scheduling function for selecting on the basis of need and overlay edge probability