[Tinyos-devel] retransmissions in networking protocols

Andreas Koepke koepke at tkn.tu-berlin.de
Fri Oct 5 02:00:33 PDT 2007


Just one more remark on where to put the L2 retransmissions (MAC vs.
routing protocol).

It seems that we have a funny situation: because net and core did not
yet agree on how to communicate link costs from PHY to anyone, all net
protocols in T2 usually assume a CC2420 radio, often with the additional
assumption that it is a plain CSMA and not a preamble sampling CSMA or
some other energy saving MAC protocol is used. The first assumption is
easily to be seen in the wiring, the second one in the way how
retransmissions are done (lqi retries immediately, ctp tries to be a bit
more platform independent, but retries after 4-32ms).  So we end up in a
situation were the routing protocol retries are more "immediate" than
the MAC protocol retransmissions ;-)

Best, Andreas



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