[ns] buffering and pkt transmission.

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

Hello ns users,

I have a basic question related to buffering and pkt transmission.

Consider a source router R. R is supposed to generate traffic
havings pkts of size 500 bytes. The interval between pkt
transmission is 0.004 secs. The outgoing link has a bandwidth of of
10 Mbps.

 	The scenario is something like this ....


		Traffic Source	
			 ----           10 Mbps
			| R  |----------------------------->	
			 ----
		500 bytes pkt.
		0.004 sec pkt interval.
		Start flow at 1 sec.

	Now if the first bit of the first pkt left router at 1 sec
then the last bit of the same pkt will leave at 
	
		1 sec + ( 500 * 8 b / 10Mbps ) = 1 + 0.004 = 1.004 sec.

So the first pkt is completely transmitted at 1.004 sec.

Please give pointers to the following questions ...

(1) At what time-stamp is the pkt queued ? .
(2) At what time-stamp is it dequed ?  ( is it 1.004 sec ?).
(3) If the link speed were say 100Kbps ,when will R drop a pkt ?

	Do we have a general formula for the last question ?.


I appreciate your help and thanks in advance.

Sincerely,
Abrar.