[e2e] What's wrong with this picture?
ljorgenson at apparentnetworks.com
Tue Sep 8 09:29:08 PDT 2009
Satellite link? Probably geostationary from the looks of it (around
600ms RTT) - possibly more than one bounce in certain cases. The
buffers on satellite link modems can be quite large to boot. Little to
no loss is not surprising given their retransmit capabilities.
Apparently part of a fail-over if it returned to terrestrial values in
That accounts for anything up to about 2 seconds. The really high 5-10
second RTTs still seem pretty extreme even for satellites....
t 604 433 2333 ext 105
m 604 250-4642
Date: Sun, 06 Sep 2009 21:00:16 -0400
From: "David P. Reed" <dpreed at reed.com>
Subject: [e2e] What's wrong with this picture?
To: end2end-interest list <end2end-interest at postel.org>
Message-ID: <4AA45B20.6030705 at reed.com>
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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.)
$ ping lcs.mit.edu
PING lcs.mit.edu (126.96.36.199) 56(84) bytes of data.
64 bytes from zermatt.csail.mit.edu (188.8.131.52): icmp_seq=1 ttl=44
64 bytes from zermatt.csail.mit.edu (184.108.40.206): icmp_seq=2 ttl=44
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