[Olsr-dev] OLSRd 0.5.4 and 0.5.5 with ETT available

Henning Rogge (spam-protected)
Thu Nov 13 10:10:12 CET 2008

Am Thursday 13 November 2008 09:59:55 schrieb Daniel Nitzpon:
> what about the mechanism with measuring timing of deliberate small/large
> IP-packets? why did you drop this version?
There are two problems with packet-pairs...

first, WLAN is a "collision avoidance" medium, so WLAN drivers may wait for a 
longer time until they start to send the package (longer than the whole 
transmission will take). This waiting time is independant for each package.

second, the time delay in the operation system between kernel and userspace is 
sometimes larger than the WLAN transmission time too.

Maybe you could make packet-pair work by using radiotap header for sender AND 
receiver (so you know the exact times), but if you have enough CPU power for 
radiotap you don't need packet-pairs.

But the most important problem with bandwith measurements is that you can only 
measure bandwith if there is traffic on the link. So you have to spam unicast 
packages to each of your neighbors and waste lots of airtime.


Diplom Informatiker Henning Rogge
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Angewandte Naturwissenschaften e. V. (FGAN) 
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