ndt-users list created

[Richard Carlson <>]

Hi Itamar;

The NDT system was designed to provide more details than just the 
achieved speed between the client and server.  It obtains a wealth of 
information from the Web100 variables that can explain what the TCP 
stack was actually doing during the test.  To start the debugging 
process do the following:

1) run a test from a browser or if using the command line client us 
the -ll option (web100clt -lln server) to get all the details.

2) Look at the main page, what does the "slowest link in the 
end-to-end path" message say?  Does it agree with what you expect?

3) Are there any other messages printed on the main page?

4) click on the "Statistics" button.  What does this page say?  Look 
at the "Round trip time" value, is it reasonable? How about packet 
loss/retransmission rates.  How much time was spend in the 
"connection stalled" state?  Where was the server spending most of 
its time (sender, receiver, or network limited).

5) click on the "More Details" button.  This give you a list of 
web100 variables and there values.  What was the MaxCwnd 
value?  Scroll down to the bottom of this window, what is the 
"theoretical network limit"?

6) logon to the ndt server and look at the 
/usr/local/ndt/web100srv.log file.  Every test is recorded in this 
log file using a comma (,) separated list.  A sample extract is 
"Aug  2 08:53:33,71.239.149.252,952,8679,1510,"  This is a test I 
just ran from my home PC using a cable modem link.  The variables are
        date/time of test
        Clients IP address
        s2c speed with limited Cwnd (952 Kbps here)
        s2c speed with unlimited Cwnd (8.7 Mbps here)
        c2s speed (1.5 Mbps here).

If the Cwnd limited s2c speed is greater than the Cwnd unlimited 
speed, then look for a duplex mismatch condition somewhere in the path.

Feel free to send these details to the list and we can help you 
interpret the results.

Rich
At 02:20 AM 8/2/2007, Itamar wrote:

> Hi Richard and all,
>
>
> Sorry is this is a lame one but I could not find any resembling reference.
>
> I have installed NDT on a Debian machine.
>
> When I run the test on a windows client, through an Ethernet switch, 
> using the applet I get 94 Mbps on the C2S and only 300 Kbs on teh S2C.
>
>
> Could you speculate on the reason for this?
>
> What other info do you need from my system?
>
>
> Regards,
>
> Itamar Landsman

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Richard A. Carlson                              e-mail: 

Network Engineer                                phone:  (734) 352-7043
Internet2                                       fax:    (734) 913-4255
1000 Oakbrook Dr; Suite 300
Ann Arbor,  MI  48104