Incorrect Throughput Summaries in UDP?

[Yee-Ting Li <yt...@he...>]

Hello,

We're trying to do some iperf tests through an uncongested network using UDP 
streams, reporting the rate every 2 seconds for 1 minute. We're using iperf 
1.6.5 with pthreads and we get some strange reporting of the summary result:


------------------------------------------------------------
Server listening on UDP port 5010
Receiving 1472 byte datagrams
UDP buffer size: 2097152 Byte (WARNING: requested 1048576 Byte)
------------------------------------------------------------
[  3] local xxx.xxx.xxx.xxx port 5010 connected with 
xxx.xxx.xxx.xxx port 32769
[ ID] Interval       Transfer     Bandwidth       Jitter   Lost/Total 
Datagrams
[  3]  0.0- 2.0 sec  204248832 Bytes  816993694 bits/sec  0.015 ms 
41676/180432 (23%)
[  3]  0.0- 2.0 sec  2 datagrams received out-of-order
[  3]  2.0- 4.0 sec  200495232 Bytes  801980527 bits/sec  0.016 ms 
45147/181353 (25%)
[  3]  4.0- 6.0 sec  199322048 Bytes  797289787 bits/sec  0.011 ms 
45986/181395 (25%)
[  3]  6.0- 8.0 sec  199009984 Bytes  796037946 bits/sec  0.007 ms 
46202/181399 (25%)
[  3]  8.0-10.0 sec  199110080 Bytes  796411251 bits/sec  0.031 ms 
46153/181418 (25%)
[  3] 10.0-12.0 sec  199123328 Bytes  796523978 bits/sec  0.013 ms 
46182/181456 (25%)
[  3] 12.0-14.0 sec  199288192 Bytes  797152369 bits/sec  0.025 ms 
46043/181429 (25%)
[  3] 14.0-16.0 sec  199408896 Bytes  797552240 bits/sec  0.028 ms 
46029/181497 (25%)
[  3] 16.0-18.0 sec  199332352 Bytes  797412738 bits/sec  0.012 ms 
46090/181506 (25%)
[  3] 18.0-20.0 sec  196868224 Bytes  787472109 bits/sec  0.025 ms 
47720/181462 (26%)
[  3] 20.0-22.0 sec  194798592 Bytes  779195147 bits/sec  0.014 ms 
49125/181461 (27%)
[  3] 22.0-24.0 sec  194883968 Bytes  779420907 bits/sec  0.030 ms 
49077/181471 (27%)
[  3] 24.0-26.0 sec  194845696 Bytes  779424093 bits/sec  0.028 ms 
49066/181434 (27%)
[  3] 26.0-28.0 sec  194858944 Bytes  779509829 bits/sec  0.013 ms 
49097/181474 (27%)
[  3] 28.0-30.0 sec  195091520 Bytes  780318871 bits/sec  0.029 ms 
48976/181511 (27%)
[  3] 30.0-32.0 sec  194680832 Bytes  778715151 bits/sec  0.025 ms 
49238/181494 (27%)
[  3] 32.0-34.0 sec  196510528 Bytes  786080630 bits/sec  0.029 ms 
47969/181468 (26%)
[  3] 34.0-36.0 sec  199289664 Bytes  797175397 bits/sec  0.017 ms 
46106/181493 (25%)
[  3] 36.0-38.0 sec  199210176 Bytes  796770190 bits/sec  0.041 ms 
46157/181490 (25%)
[  3] 38.0-40.0 sec  199313216 Bytes  797323826 bits/sec  0.019 ms 
46024/181427 (25%)
[ ID] Interval       Transfer     Bandwidth       Jitter   Lost/Total 
Datagrams
[  3] 40.0-42.0 sec  199375040 Bytes  797390917 bits/sec  0.028 ms 
45999/181444 (25%)
[  3] 42.0-44.0 sec  200144896 Bytes  800570377 bits/sec  0.029 ms 
45466/181434 (25%)
[  3] 44.0-46.0 sec  199370624 Bytes  797549490 bits/sec  0.022 ms 
45984/181426 (25%)
[  3] 46.0-48.0 sec  199458944 Bytes  797878462 bits/sec  0.030 ms 
45885/181387 (25%)
[  3] 48.0-50.0 sec  101038080 Bytes  404154543 bits/sec  0.026 ms 
113310/181950 (62%)
[  3] 50.0-52.0 sec  199441280 Bytes  797706887 bits/sec  0.021 ms 
45894/181384 (25%)
[  3] 52.0-54.0 sec  197998720 Bytes  792020621 bits/sec  0.025 ms 
46817/181327 (26%)
[  3] 54.0-56.0 sec  199107136 Bytes  796465181 bits/sec  0.013 ms 
46163/181426 (25%)
[  3] 56.0-58.0 sec  200219968 Bytes  800880673 bits/sec  0.022 ms 
45416/181435 (25%)
[  3] 58.0-60.0 sec  197239168 Bytes  788955489 bits/sec  0.012 ms 
47441/181435 (26%)
[  3]  0.0-60.0 sec  1559126656 Bytes  207849079 bits/sec  0.012 ms 
1466661/5443627 (27%)
[  3]  0.0-60.0 sec  2 datagrams received out-of-order



As you can see, the summary rate is much smaller than that reported by the 
regular intervals; also, the total number of bytes transfered is about a third 
less than the accumulated count.

We repeated the test a few times and the report is similar in all tests.


Any comments/suggestions appreciated!

Yee.



-- 
*************************************************************************
 Yee-Ting Li                                    email: yt...@he...
 High Energy Particle Physics              http://www.hep.ucl.ac.uk/~ytl
 University College London                     Tel: +44 (0) 20 7679 1376
 Gower Street                                  Fax: +44 (0) 20 7679 7145
 London, WC1E 6BT
 United Kingdom
*************************************************************************