Re: [ns] bidirectional elements

[Sudhindra Suresh Bengeri <ssbenger@unity.ncsu.edu>]

Hi Nimrod,

Just a wild idea.
If you want to observe TCP traffic on an intermediate node, you will have
to write a pseudo-classifier, register your object as the classifier at
that node, check if the packet received is a TCP packet, if so do the
required processing. In any case hand it over to the classifier
(normally Classifer/Hash/Dest) object.
 
This will ensure that all the traffic that passes through this node/or is
destined to this node is received by your object. 

To do this you may have to change the init code of node
(tcl/lib/ns-node.tcl), if you have installed tcl-debugger you will have a
better idea of the sequence of events that take place when the $ns node is
called.

Hope it helps.

Regards,
Sudhin.


On Fri, 19 May 2000, Nimrod Mesika wrote:

> Is it possible to create a node (or any other object) that receives all
> traffic going through this node in BOTH directions? (and can tell
> whether its going in one direction or the other).
> 
> I want to create an object that receives all TCP traffic passing through
> a certain node in the network (in both directions). That object should
> be able to drop packets, delay packets etc., and of course must handle
> multiple flows with different source nodes and destinations.
> 
> I have been unable to find anything resembling this behaviour in ns as
> it seems the simulator uses internally unidirectional links (except for
> LANs and wireless object which I'm not interested in right now). The
> Snoop module might be similar to what I'm looking for but it's WAY too
> complicated and I don't even have a simple tcl example for snoop...
> 
> Can anyone point me to the right direction?
> 
> Thanks,
> -- Nimrod.
> 

****************** Sudhindra Suresh Bengeri *******************
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