Hi Sugang,

Michael's explanation is 100% correct. You can try setting the retries on the
sender to another value by calling:
`ifconfig <ID> set csma_retries <NUMBER>`
and should see different results.

Cheers,
Oleg

On Fri, Jan 29, 2016 at 01:57:34PM -0800, Michael Andersen wrote:
> Hi
> 
> Generally if you are sending unicast, and there is no receiver, you will
> see multiple copies of the packet as the transmitter is expecting an ACK,
> and will retry until it gets one or it reaches the max number of retries.
> There are no ACKs on broadcast, so the transmitter will only send one.
> 
> Regards
> Michael
> 
> On Fri, Jan 29, 2016 at 12:51 PM, Sugang Li <[email protected]> wrote:
> 
> > Hi all,
> >
> > I am working on sniffer testing over SAMR21 board,  here is my setup:
> >
> > 1. I have one node to send mac packet by calling txtsend.
> > 2. Another node is working as a Sniffer which is in the Promisc Mode set
> > by "ifconfig set promisc"
> >
> > However, whenever the transmitter send one pkt via unicast, the sniffer
> > will receiver will receive 4 pkt (each of them will have a different header
> > memory address).   If it sends via broadcast mode, the sniffer only got one
> > pkt (this is correct).
> >
> > Any idea about this weird situation?
> >
> > Thanks,
> >
> > Sugang
> >
> > --
> >
> > *WINLAB, Department of Electrical and Computer Engineering*
> >
> > *Rutgers,the State University of New Jersey*
> >
> > _______________________________________________
> > devel mailing list
> > [email protected]
> > https://lists.riot-os.org/mailman/listinfo/devel
> >
> >

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