[Ns-bugs] [Bug 189] CSMA device receives all packets it sends

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http://www.nsnam.org/bugzilla/show_bug.cgi?id=189





------- Comment #6 from mathieu.lacage at sophia.inria.fr  2008-05-30 16:55 -------
(In reply to comment #5)
> That depends on whether or not you ever want to have a device that receives its
> own transmissions.

I have never seen a device like this.

> Right now every device receives every packet and filters it according to
> destination, multicast and broadcast address.  One way to proceed is to filter
> according to source, destination, multicast and broadcast.
> 
> As you mention, another way is to filter source in the channel.  However, in
> reality there is no logic in a wire, so this strikes me as an odd place to
> perform filtering.  Therefore, I was planning on adding the filtering to the
> device.
> 
> Tom says that he knows of no case where a CSMA device would ever receive a
> packet that it sends since the receiver is disabled during transmit to avoid
> spurious collision detection.  Still, I think the right place to do the
> filtering is on the device and not "inside the wire."

There might be reasons to implement this feature that way because of the
current implementation and the output might look exactly the same but this
really strikes me as very weird from a modelization perspective. It is also
slightly sub-optimal because you have to perform one packet copy per receiver
to immediately destroy it in the case the receiver is also the transmitter.

But well, in the end, I cannot make myself care much provided we get
nice-looking coherent pcap output.


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