ndt-users list created

[Richard Carlson <>]

Hi Kenny;

Here's a copy of the stuff I add to my /etc/sysctl.conf file.

# NEW parameter for 2.6.13 kernels.  Set to Reno style CC
net.ipv4.tcp_congestion_control = reno

# TCP Tuning data added 7/28/05 RAC
# increase Linux TCP buffer limits
net.core.rmem_max = 33554432
net.core.wmem_max = 33554432
net.core.rmem_default = 65535
net.core.wmem_default = 65535

# increase Linux autotuning TCP buffer limits
net.ipv4.tcp_rmem = 4096 87380 16777216
net.ipv4.tcp_wmem = 4096 65535 16777216
# net.ipv4.tcp_mem = 1024 65535 524288

# Turn on Explicit Congestion Notification (ECN) processing
net.ipv4.tcp_ecn = 1

A few things to note.

The INSTALL file that comes with the NDT package is suppose to have this 
information.  Unfortunately the current tarball contains a generic GNU 
based INSTALL file.  The NDT specific version has been returned and future 
tarballs will contain this tuning info.

Also note that the net.ipv4.tcp_mem settings are commented out.  Looking at 
the Linux documentation it appears that the kernel does a better job of 
setting the right values than manual intervention.  I recommend letting the 
kernel handle this.

One last thing, the latest Linux 2.6.x kernels do autotuning.  Thus these 
tuning values try and set both reasonable default (64KB) and max limits (16 
- 32 MB).  This autotuning can be turned off by using the NDT "-b value" 
option.  I don't recommend using this option, but it is there in case you 
need it.

To learn more about this follow the links on the main NDT web page to the 
PSC and LBNL tuning pages.  Or google "tcp tuning" to find these pages.

Rich

At 06:32 AM 10/13/2006, Ken Bellars wrote:


> I have my NDT running perfectly now.
>
> I however noticed that editing the config file sysctl.conf  affects the 
> report.
>
> I need to know the best config for the more close to accrate report
>
> Thank you.
>
> Kenny

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Richard A. Carlson                              e-mail: 

Network Engineer                                phone:  (734) 352-7043
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