how to do probabilistic packet loss in kernel?

how to do probabilistic packet loss in kernel?

[George P Nychis]

Hi,

I am using iproute2 to setup fowarding, adding routes like "ip route add 192.168.1.3 via 192.168.1.2"

I was wondering where in the kernel I can insert probabilistic packet loss only for forwarded packets?  So that for instance I can drop 5% of all forwarded packets?

I don't need help with the actual code, just need help finding where to insert this code :)

Thanks!
George

Re: how to do probabilistic packet loss in kernel?

[Ian McDonald]

On 4/17/06, George P Nychis <gnychis@cmu.edu> wrote:
> Hi,
>
> I am using iproute2 to setup fowarding, adding routes like "ip route add 192.168.1.3 via 192.168.1.2"
>
> I was wondering where in the kernel I can insert probabilistic packet loss only for forwarded packets?  So that for instance I can drop 5% of all forwarded packets?
>
Have a look at:
http://linux-net.osdl.org/index.php/Netem

--
Ian McDonald
Web: http://wand.net.nz/~iam4
Blog: http://imcdnzl.blogspot.com
WAND Network Research Group
Department of Computer Science
University of Waikato
New Zealand

Re: [offlist] Re: [LARTC] how to do probabilistic packet loss in kernel?

[George Nychis]

Hey Martin,

I was able to do it with netem and its working great now.

I've actually moved on to another challenge, I would like to drop 
packets at the hardware level such as to see rate control.

Because when netem drops a packet, TCP responds, however the lower level 
card will not interact because it never sees the loss.

What I want to do is somehow cause the card to send a corrupted packet 
based on a probability, or not send the packet but make it think that it 
did.

I'm using madwifi and I've found in the code where it does rate control 
and sends out the data, so i'm hoping to make this happen, but having 
troubles!

So if anyone else has any ideas on how to get rate control interactive 
packet loss, i'd love it.

- George


Martin A. Brown wrote:
> Hello George,
> 
> Unfortunately, I cannot answer your most recent question.  I'm 
> hoping that Stephen Hemminger can answer your question.  He is 
> subscribed to the LARTC list, is also the author of netem and 
> seems to be a smart cookie.
> 
> Good luck,
> 
> -Martin
> 

Re: [offlist] Re: [LARTC] how to do probabilistic packet loss in kernel?

[Ian McDonald]

On 4/20/06, George Nychis <gnychis@cmu.edu> wrote:
> Hey Martin,
>
> I was able to do it with netem and its working great now.
>
> I've actually moved on to another challenge, I would like to drop
> packets at the hardware level such as to see rate control.
>
Have a look at:
http://linux-net.osdl.org/index.php/Netem#Rate_control

Works well for me...

Ian
--
Ian McDonald
Web: http://wand.net.nz/~iam4
Blog: http://imcdnzl.blogspot.com
WAND Network Research Group
Department of Computer Science
University of Waikato
New Zealand