[Tinyos-devel] retransmissions in networking protocols

[Omprakash Gnawali]

In terms of software architecuture, are we talking about hop-by-hop
retransmission or MAC level retransmission?

In net2, we had a related discussion a while ago. Please also go to
this page:
http://mail.millennium.berkeley.edu/pipermail/net2-wg/2007/date.html

and read the discussion with subject:

"L2 retx and CTP FE"



- om_p

> I'd vote for including hop by hop filtering if we have hop by hop
> retransmissions in the network protocols. Or remove retransmissions from
> the network and let the MAC/LinkLayer do this kind of stunts.
> 
> Best, Andreas
> 
> Matt Welsh wrote:
> > Actually these protocols perform retransmissions at the *link* layer,
> > not the network layer (the latter would imply end-to-end).
> > 
> > I'm firmly in the camp that link-layer ARQ is a necessity with these
> > kinds of radios, due to interference and collisions (the MAC could
> > perhaps be tuned to help avoid the latter).  Better route selection -
> > choosing only 'symmetric' links - can cut down on duplicate packets. One
> > could imagine a node detecting many duplicates from its children telling
> > those children to reduce their ARQ threshold. Even so I think filtering
> > out duplicates hop-by-hop or at the base station is perfectly
> > acceptable.
> > 
> > On Thu, 2007-10-04 at 14:02 +0200, Andreas Koepke wrote:
> > 
> >>Hi guys in the net group,
> >>
> >>looks like MultihopLqi and Ctp all do retransmissions on the network
> >>level if the MAC reports a transmission failure. So whenever the MAC did
> >>not receive an ACK the packet is duplicated. This happens quite often in
> >>our testbed, because the TX power of the nodes seems to have a
> >>siginficant variance.
> >>
> >>What is your experience, should we do something about it?
> >>
> >>Best, Andreas
> >>
> >>_______________________________________________
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> > 
> > 
> > 
> 
> 
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