[Tinyos-devel] retransmissions in networking protocols

[Andreas Koepke]

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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> 
> 
>