Initialization of network simulator event

Things to remember when initialization of network simulator, Ns-2

When a new simulation object is created in tcl, the initialization procedure performs the following operations:

• initialize the packet format (calls create_packetformat)
• create a scheduler (defaults to a calendar scheduler)
• create a "null agent" (a discard sink used in various places)

** Ns-2 is an event-driven simulator, therefore scheduler is a crucial component for simulation to determine all the events to be simulated accordingly.

There are 4 different types of scheduler that is created by using a different data structure:

1. a simple linked-list,
2. heap,
3. calendar queue (default)
4. and a special type called "real-time".

The actual definition of event is found is ~ns/scheduler.h

class Event {
public;
Event* next_; /* event list */
Handler* handler_; /* handler to call when event ready */
double time_; /* time at which event is ready */
int uid_; /* unique ID */
Event() : time_(0), uid_(0) {}
};
/*
* The base class for all event handlers. When an event’s scheduled
* time arrives, it is passed to handle which must consume it.
* i.e., if it needs to be freed it, it must be freed by the handler.
*/
class Handler {
public:
virtual void handle(Event* event);
};