NS2 Dropped Packets

Question

hello everyone : i got this results when i run AODV for 60 node for 600s area is 100X100 max speed 10m/s: ,generated packets == 95364,sent==95364,lost=112,dropped=112786,max delay=0.00899

is it true that the number of dropped packet is greater than the generated one???? pls anyone can explain that??? if there is simulation wrong pls tell me .

another question what dropped packet exactly mean in NS2 ??? dose it contain the intermediate node dropped packet?

thanks in advance

Answer 1

You might calculate the retransmitting dropped packets because once a packet being dropped, mac layer retransmits the packet again.

Note: don't calculate the packet those dropped at the end of simulation, those with drop reason is 'END'

Answer 2

In Network simulator 2 trace file generally;

Column 1 represents event type (s: send, r: receive, d: drop, f: forward)

Columns 2 and 3 provide time of the event.

Columns 4 to 7 provide next-hop information.

Columns 8 to 21 are called node property tags.

Column 11 gives the reason for a packet drop and the various reasons possible for a packet drop are as follows.

END drop due to end of simulation

COL drop due to collision at MAC layer

DUP drop due to duplicate packet

ERR drop due to MAC packet error

RET drop due to exceeding retry count

STA drop due to MAC invalid state

BSY drop due to MAC busy

NRTE drop due to no route available

LOOP drop due to routing loop

TTL drop due to TTL=0

TOUT drop due to packet expired

IFQ drop due to no buffer space in IFQ

ARP dropped ARP

OUT dropped by base stations

You may analyze your dropped packets by grouping them with the reasons.

Answer 3

It is not possible that dropped packet is greater than generated (send) packets. Check your script that you have to count the packets drop in AGT layer not in mac layer.

try to find the values using the below awk script.

BEGIN {

        sendLine = 0;

        recvLine = 0;

        fowardLine = 0;

        dropLine = 0;

}



$0 ~/^s.* AGT/ {

        sendLine ++ ;

}



$0 ~/^r.* AGT/ {

        recvLine ++ ;

}



$0 ~/^f.* RTR/ {

        fowardLine ++ ;

}


$0 ~/^D.* cbr/ {

        dropLine ++ ;

}

END {
printf "Packet Sent: %d\n,sendLine"
printf "Packet Received: %d\n,recvLine"
printf "Packet Drop: %d\n,dropLine"


        printf "PacketDelivery Ratio:%.4f \n",(recvLine/sendLine);
}

Answer 4

Well, you cannot drop more packets than you generate. Usually you drop them at the bottleneck queue, where they overflow the queue.