[e2e] What's wrong with this picture?

Arthur Callado arthurcallado at gmail.com
Tue Sep 8 10:54:28 PDT 2009

And 5-10 seconds RTT seems too little for IPN (http://www.ipnsig.org),
no matter what planet. Or are you pinging from the Earth's Moon? That
RTT would be reasonable (without equipment failure) in a moon-to-earth
scenario, but I wonder what reason you gave for an agency to fund such
an endeavor.

Arthur Callado.
Networking and Telecommunications Research Group
Federal University of Pernambuco, Brazil

On Tue, Sep 8, 2009 at 1:29 PM, Loki
Jorgenson<ljorgenson at apparentnetworks.com> wrote:
> 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
> the morning.
> That accounts for anything up to about 2 seconds.  The really high 5-10
> second RTTs still seem pretty extreme even for satellites....
> Loki Jorgenson
> Apparent Networks
> t   604 433 2333 ext 105
> m   604 250-4642
> -----Original Message-----
> Message: 1
> 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>
> Content-Type: text/plain; charset="iso-8859-1"
> 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 ( 56(84) bytes of data.
> 64 bytes from zermatt.csail.mit.edu ( icmp_seq=1 ttl=44
> time=6330 ms
> 64 bytes from zermatt.csail.mit.edu ( icmp_seq=2 ttl=44
> time=6005 ms

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