[Click] Filtering TCP ACks

[Eddie Kohler]

Hi Roberto,

If all you want is to filter pure acks (i.e. with length 0), try "tcp ack && 
not tcp syn && not tcp fin && ip len < 100".  You're right that this is not 
perfect; there's no way with a pure IPFilter/IPClassifier to check that the 
TCP length is 0.

Eddie


Roberto Riggio wrote:
> Hi,
> 
> I have I problem in filtering the TCP ACKs. I'm generating traffic between 
> two nodes:
> 
> A -> B
> 
> I would like to filter the ACk at node A. However filtering the packets using 
> the IPCLassifier element is not working since the ACK field is set to TRUE 
> even for the segments travelling from A to B (in this case the ACK number is 0)
> 
> The only workaround that I've managed to find is to use the element CheckLength
> in order to filter all the packets longer the 100 byte. In my particular case 
> such an approach is fine, but I'm wondering if there is a correct solution to my
> problem.
> 
> Bye
>