[ns] time in ns

[abrar hussain <ahussain@eng.utoledo.edu>]

Hello ns users,

 	I am not sure about how ns maintains its simulation time.
How all the nodes are able to print the current time ? .

	I have seen a nam trace file, and i saw that it was maintaining
the simualtion time in seconds, but i am not sure how is it done and where 
is it done.

 Any pointers are welcome.

 Thanks for ur help.

Abrar.