[e2e] What's wrong with this picture?

Tue Sep 8 11:04:15 PDT 2009

The fact that the TTL value is 44 in the response makes me hazard a guess
that there are routing issues with the IAP (sounds like MPLS may be
involved).

On Sun, Sep 6, 2009 at 6:00 PM, David P. Reed <dpreed at reed.com> wrote:

>  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...
>
> (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.)
>
> 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).
>
> $ ping lcs.mit.edu
> PING lcs.mit.edu (128.30.2.121) 56(84) bytes of data.
> 64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=1 ttl=44
> time=6330 ms
> 64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=2 ttl=44
> time=6005 ms
> 64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=3 ttl=44
> time=8509 ms
> 64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=4 ttl=44
> time=9310 ms
> 64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=5 ttl=44
> time=8586 ms
> 64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=6 ttl=44
> time=7765 ms
> 64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=7 ttl=44
> time=7168 ms
> 64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=8 ttl=44
> time=10261 ms
> 64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=9 ttl=44
> time=10624 ms
> 64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=10 ttl=44
> time=9625 ms
> 64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=11 ttl=44
> time=9725 ms
> 64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=12 ttl=44
> time=8725 ms
> 64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=13 ttl=44
> time=9306 ms
> 64 bytes from zermatt.csail.mit.edu (128.30.2.121): icmp_seq=14 ttl=44
> time=8306 ms
> ^C
> --- lcs.mit.edu ping statistics ---
> 24 packets transmitted, 14 received, 41% packet loss, time 33174ms
> rtt min/avg/max/mdev = 6005.237/8589.365/10624.776/1334.140 ms, pipe 11
> $ traceroute lcs.mit.edu
> traceroute to lcs.mit.edu (128.30.2.121), 30 hops max, 60 byte packets
>  1  * * *
>  2  172.26.248.2 (172.26.248.2)  693.585 ms  693.415 ms  712.282 ms
>  3  * * *
>  4  172.16.192.18 (172.16.192.18)  712.700 ms  1356.680 ms  1359.469 ms
>  5  12.88.7.205 (12.88.7.205)  1361.306 ms  673.642 ms  673.541 ms
>  6  cr84.cgcil.ip.att.net (12.122.152.134)  673.442 ms  673.371 ms
> 673.742 ms
>  7  cr2.cgcil.ip.att.net (12.123.7.250)  655.126 ms  654.186 ms  554.690
> ms
>  8  * * ggr2.cgcil.ip.att.net (12.122.132.133)  912.385 ms
>  9  192.205.33.210 (192.205.33.210)  909.925 ms  911.335 ms  911.204 ms
> 10  ae-31-53.ebr1.Chicago1.Level3.net (4.68.101.94)  569.740 ms  569.605
> ms  907.409 ms
> 11  ae-1-5.bar1.Boston1.Level3.net (4.69.140.93)  369.680 ms  344.495 ms
> 345.252 ms
> 12  ae-7-7.car1.Boston1.Level3.net (4.69.132.241)  355.645 ms  641.866 ms
> 641.367 ms
> 13  MASSACHUSET.car1.Boston1.Level3.net (4.53.48.98)  636.598 ms  636.797
> ms  635.755 ms
> 14  B24-RTR-2-BACKBONE-2.MIT.EDU (18.168.1.23)  635.766 ms  634.794 ms
> 866.430 ms
> 15  MITNET.TRANTOR.CSAIL.MIT.EDU (18.4.7.65)  758.305 ms  822.244 ms
> 821.202 ms
> 16  trantor.kalgan.csail.mit.edu (128.30.0.246)  833.699 ms  1055.548 ms
> 1116.813 ms
> 17  zermatt.csail.mit.edu (128.30.2.121)  1114.838 ms  539.951 ms  620.681
> ms
> [david at whimsy ~]$ ping 172.26.248.2
> PING 172.26.248.2 (172.26.248.2) 56(84) bytes of data.
> 64 bytes from 172.26.248.2: icmp_seq=1 ttl=254 time=1859 ms
> 64 bytes from 172.26.248.2: icmp_seq=2 ttl=254 time=1363 ms
> 64 bytes from 172.26.248.2: icmp_seq=3 ttl=254 time=1322 ms
> 64 bytes from 172.26.248.2: icmp_seq=4 ttl=254 time=1657 ms
> 64 bytes from 172.26.248.2: icmp_seq=5 ttl=254 time=1725 ms
> 64 bytes from 172.26.248.2: icmp_seq=6 ttl=254 time=1740 ms
> 64 bytes from 172.26.248.2: icmp_seq=7 ttl=254 time=1838 ms
> 64 bytes from 172.26.248.2: icmp_seq=8 ttl=254 time=1738 ms
> 64 bytes from 172.26.248.2: icmp_seq=9 ttl=254 time=1517 ms
> 64 bytes from 172.26.248.2: icmp_seq=10 ttl=254 time=978 ms
> 64 bytes from 172.26.248.2: icmp_seq=11 ttl=254 time=715 ms
> 64 bytes from 172.26.248.2: icmp_seq=12 ttl=254 time=678 ms
> 64 bytes from 172.26.248.2: icmp_seq=13 ttl=254 time=638 ms
> 64 bytes from 172.26.248.2: icmp_seq=14 ttl=254 time=761 ms
> ^C
> --- 172.26.248.2 ping statistics ---
> 15 packets transmitted, 14 received, 6% packet loss, time 14322ms
> rtt min/avg/max/mdev = 638.651/1324.002/1859.725/455.200 ms, pipe 2
> $
>
>
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