ndt-users list created

[Richard Carlson <>]

Chris/Jeremy;

As Charlie Brown use to say AAAAAARRRRRGGGGGHHHH!!!

Sorry for the delay, travel and meetings have kept me from getting 
this reply out sooner.  I looked at the tcpdump traces you both sent 
and they show what I expect, the traffic to/from port 7123 is the 
initial connection where the applet is downloaded to the 
client.  Traffic on port 3001 is the control info, where the server 
and client communicate to run the specific tests.  Traffic on port 
3003 is the data test for the middlebox test.

This test is suppose to stream data from the server to the client for 
5 seconds with a limited Congestion Window.  The server also tries to 
restrict the amount of data it dumps to the stack so the server does 
not queue a lot of data.  Both the client and server run watchdog 
timers to prevent this test from running forever.

It looks like the server is failing to find the proper web100 
connection ID so the limits are not being set/used.  The server 
process sends data to the stack faster than the stack can sent it out 
on the network.  Thus a queue builds up in the server (you should see 
this with a netstat -nat command) so when the 5 sec send timer 
expires there is still data in the queue that needs to be sent to the 
client.  The client's watchdog timer is reached and it kills the 
client, while the server is still in trying to deliver the 
packets.  Finally the server's watchdog timer goes off, and the server exits.

There are a couple of options we can take to work around this 
problem, and I'll experiment with them to see what works 
best.  I'll  push out a new test version soon and let you know when it's ready.

Regards;
Rich;

PS thanks for the script patch, I really appreciate patches and 
updates that help make the tool better for the community.

At 08:22 AM 7/19/2007, Christopher Nicholas Florio wrote:
> That's funny, I was delayed in getting those flows because I also 
> made the machine to a kernel panic when trying to unload ipv6 (and 
> the machine is in a different building from my office).
>
> I'll get that tcpdump results out today as well.
>
> Thanks!!!
>
> Chris Florio
> ITS Control Center
> 211 Manning Drive
> Suite 3001, ITS Manning Bldg
> CB 3420
> Chapel Hill, NC 27599
> 919-843-8310 (o)
> 919-208-3905 (c)

[snip snip snip]


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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