On dublin

On Dublin:

[root@dublin /root]# . dump64 2>&1 | tee 369Dublin

Where: dump64 is script file whose content is: tcpdump -i eth2 -l dst host 192.168.2.2

Note: Here tcpdump need option -l, meaning Make stdout line buffered
Otherwise, it might be a problem when you analyze the dump result.

On Prague:

[lin@prague nettest]$ pingserver 1026

On Madrid:

[lin@madrid nettest]$ . try 2>&1 | tee 369Madrid

Where try is a script file whose content is

============================
for i in `seq 1 10`;
do
echo " "
echo "/home/lin/nettest/pingclient 1026 192.168.2.2 100 32768"
echo " "
sleep 5
/home/lin/nettest/pingclient 1026 192.168.2.2 100 32768
echo " "
done

for i in `seq 1 10`;
do
echo " "
echo "/home/lin/nettest/pingclient 1026 192.168.2.2 100 65536"
echo " "
sleep 5
/home/lin/nettest/pingclient 1026 192.168.2.2 100 65536
echo " "
done

for i in `seq 1 10`;
do
echo " "
echo "/home/lin/nettest/pingclient 1026 192.168.2.2 100 98304"
echo " "
sleep 5
/home/lin/nettest/pingclient 1026 192.168.2.2 100 98304
echo " "
done
============================

Nettest Iteration Times: 100
Request Size (Byte)	1st		2nd		3rd		4th		5th		6th		7th		8th		9th		10th		AVGt	tVar
Request Size (Byte)	t	#pack	t	#pack	t	#pack	T	#pack	t	#pack	t	#pack	t	#pack	t	#pack	t	#pack	t	#pack	AVGt	tVar
32768	0.60	2300	0.60	2300	0.60	2300	0.60	2300	0.60	2300	0.60	2300	0.60	2300	0.60	2300	0.60	2300	0.60	2300	0.60	0
65536	3.22	4600	2.02	4600	2.00	4600	1.61	4600	1.41	4600	1.51	4600	1.65	4600	1.99	4600	3.69	4600	2.01	4600	2.111	0.5376
96304	1.71	6800	1.71	6800	1.72	6800	1.71	6800	1.72	6800	1.72	6800	1.71	6800	1.71	6800	1.72	6800	1.71	6800	1.714	0.0048

From the above result, we can see:

When request size is 65536, the round trip time ( RTT) is very variable. fluctuate 25% of the average RTT
This fluctuation is NOT because of TCP packet loss and retransmission. This conclusion is based on the assumption that: If some data in a given packet is loss or corrupted, the retransmission mechanism will transmit the whole packet again. And TCP retransmission can be captured by "tcpdump"

here is the Raw Data we get from Madrid

here is the Raw tcpdump Data we get from Dublin( about 27MB )

In order to calculate the number of packet we send on each iteration, we make a simple program to do that. Run this program we get the calculation result HERE