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<font face="Helvetica, Arial, sans-serif">For those who have some idea
of how TCP does congestion control, I ask "what's wrong with this
picture?" And perhaps those who know someone responsible at the
Internet Access Provider involved, perhaps we could organize some
consulting help...<br>
<br>
(Hint: the problem relates to a question, "why are there no lost IP
datagrams?", and a second hint is that the ping time this morning was
about 193 milliseconds.)<br>
<br>
Van Jacobsen, Scott Shenker, and Sally Floyd are not allowed to answer
the question. (they used to get funding from the IAP involved, but
apparently that company does not listen to them).<br>
<br>
$ ping lcs.mit.edu<br>
PING lcs.mit.edu (128.30.2.121) 56(84) bytes of data.<br>
64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=1 ttl=44
time=6330 ms<br>
64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=2 ttl=44
time=6005 ms<br>
64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=3 ttl=44
time=8509 ms<br>
64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=4 ttl=44
time=9310 ms<br>
64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=5 ttl=44
time=8586 ms<br>
64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=6 ttl=44
time=7765 ms<br>
64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=7 ttl=44
time=7168 ms<br>
64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=8 ttl=44
time=10261 ms<br>
64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=9 ttl=44
time=10624 ms<br>
64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=10 ttl=44
time=9625 ms<br>
64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=11 ttl=44
time=9725 ms<br>
64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=12 ttl=44
time=8725 ms<br>
64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=13 ttl=44
time=9306 ms<br>
64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=14 ttl=44
time=8306 ms<br>
^C<br>
--- lcs.mit.edu ping statistics ---<br>
24 packets transmitted, 14 received, 41% packet loss, time 33174ms<br>
rtt min/avg/max/mdev = 6005.237/8589.365/10624.776/1334.140 ms, pipe 11<br>
$ traceroute lcs.mit.edu<br>
traceroute to lcs.mit.edu (128.30.2.121), 30 hops max, 60 byte packets<br>
1 * * *<br>
2 172.26.248.2 (172.26.248.2) 693.585 ms 693.415 ms 712.282 ms<br>
3 * * *<br>
4 172.16.192.18 (172.16.192.18) 712.700 ms 1356.680 ms 1359.469 ms<br>
5 12.88.7.205 (12.88.7.205) 1361.306 ms 673.642 ms 673.541 ms<br>
6 cr84.cgcil.ip.att.net (12.122.152.134) 673.442 ms 673.371 ms
673.742 ms<br>
7 cr2.cgcil.ip.att.net (12.123.7.250) 655.126 ms 654.186 ms
554.690 ms<br>
8 * * ggr2.cgcil.ip.att.net (12.122.132.133) 912.385 ms<br>
9 192.205.33.210 (192.205.33.210) 909.925 ms 911.335 ms 911.204 ms<br>
10 ae-31-53.ebr1.Chicago1.Level3.net (4.68.101.94) 569.740 ms
569.605 ms 907.409 ms<br>
11 ae-1-5.bar1.Boston1.Level3.net (4.69.140.93) 369.680 ms 344.495
ms 345.252 ms<br>
12 ae-7-7.car1.Boston1.Level3.net (4.69.132.241) 355.645 ms 641.866
ms 641.367 ms<br>
13 MASSACHUSET.car1.Boston1.Level3.net (4.53.48.98) 636.598 ms
636.797 ms 635.755 ms<br>
14 B24-RTR-2-BACKBONE-2.MIT.EDU (18.168.1.23) 635.766 ms 634.794 ms
866.430 ms<br>
15 MITNET.TRANTOR.CSAIL.MIT.EDU (18.4.7.65) 758.305 ms 822.244 ms
821.202 ms<br>
16 trantor.kalgan.csail.mit.edu (128.30.0.246) 833.699 ms 1055.548
ms 1116.813 ms<br>
17 zermatt.csail.mit.edu (128.30.2.121) 1114.838 ms 539.951 ms
620.681 ms<br>
[david@whimsy ~]$ ping 172.26.248.2<br>
PING 172.26.248.2 (172.26.248.2) 56(84) bytes of data.<br>
64 bytes from 172.26.248.2: icmp_seq=1 ttl=254 time=1859 ms<br>
64 bytes from 172.26.248.2: icmp_seq=2 ttl=254 time=1363 ms<br>
64 bytes from 172.26.248.2: icmp_seq=3 ttl=254 time=1322 ms<br>
64 bytes from 172.26.248.2: icmp_seq=4 ttl=254 time=1657 ms<br>
64 bytes from 172.26.248.2: icmp_seq=5 ttl=254 time=1725 ms<br>
64 bytes from 172.26.248.2: icmp_seq=6 ttl=254 time=1740 ms<br>
64 bytes from 172.26.248.2: icmp_seq=7 ttl=254 time=1838 ms<br>
64 bytes from 172.26.248.2: icmp_seq=8 ttl=254 time=1738 ms<br>
64 bytes from 172.26.248.2: icmp_seq=9 ttl=254 time=1517 ms<br>
64 bytes from 172.26.248.2: icmp_seq=10 ttl=254 time=978 ms<br>
64 bytes from 172.26.248.2: icmp_seq=11 ttl=254 time=715 ms<br>
64 bytes from 172.26.248.2: icmp_seq=12 ttl=254 time=678 ms<br>
64 bytes from 172.26.248.2: icmp_seq=13 ttl=254 time=638 ms<br>
64 bytes from 172.26.248.2: icmp_seq=14 ttl=254 time=761 ms<br>
^C<br>
--- 172.26.248.2 ping statistics ---<br>
15 packets transmitted, 14 received, 6% packet loss, time 14322ms<br>
rtt min/avg/max/mdev = 638.651/1324.002/1859.725/455.200 ms, pipe 2<br>
$<br>
<br>
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