I want to do some network measurements. ... / 2012-09-05

I want to do some network measurements. Measuring throughput over tcp or udp is easy: use iperf. Although the iperf server process in daemon mode was using 100% cpu for each(!) measurement somehow, so the load on the machine tested ran up to more than 50.

But I am also interested in tcp setup time. It took a bit longer to find something which does that. Searching gave me measure tcp connection setup time: time-gai-connect which was developed to measure differences in IPv4 and IPv6 tcp connection setup times. Interesting answers:

$ ./time-gai-connect.py www.google.com
2a00:1450:400c:c05::63                   19.62209 ms
173.194.78.147                           19.78207 ms
173.194.78.106                           20.66183 ms
173.194.78.105                           19.69004 ms
173.194.78.103                           20.01190 ms
173.194.78.99                            20.47896 ms
173.194.78.104                           21.71206 ms

And this one is really strange to me... on the machine which runs both the IPv4 address and IPv6 address for idefix.net:

$ ./time-gai-connect.py idefix.net
2001:980:14ca:42::18                      0.35095 ms
82.95.196.202                             0.18501 ms

Yes, the IPv6 tcp connect setup takes longer with IPv6 on this local connection.

I added code to measure resolving time when testing it on my laptop, which now shows shorter times for IPv6 than IPv4, one wireless hop away from the same system.

$ ./time-gai-connect.py idefix.net
Resolving                                 3.20196 ms
2001:980:14ca:42::18                      0.96989 ms
82.95.196.202                             1.49107 ms

Measuring this gives more new questions than answers... it seems remote destinations are faster for IPv6 than for IPv4. Example from the same laptop:

$ ./time-gai-connect.py www.xs4all.nl
Resolving                                34.10101 ms
2001:888:0:18::80                        15.76281 ms
194.109.6.92                             15.84506 ms

And from the system running idefix.net:

$ ./time-gai-connect.py www.xs4all.nl
Resolving                                 2.60282 ms
2001:888:0:18::80                        14.32490 ms
194.109.6.92                             15.16104 ms

But anyway, iperf and time-gai-connect will give me the answers I want to measure.