[Tinyos-devel] CTP - day and night

[Omprakash Gnawali]

I ran CTP for 24 hrs - 4pm till 4pm the following day. The result
tagged "aaa9" has been added to this page:
http://enl.usc.edu/~om_p/net2/ctp4bitle/figures.html

In order to put results from experiments done in the past on the same
graphs, I have changed the time scale for the past results. You can
read this on the key for the lines on the graph. For example, time * 2
means time scaled by 2. The results seem qualitatively similar to aa9,
which was the previous long experiment. The numbers are on the top of
the page and the graphs follow. I think it would be interesting to
understand the cause for loops with aaa9. It would be also interesting
to understand the temporal variation in various metrics, including
loops. Having data from a 24-hr experiment allows us to study such
temporal variations.

I plotted two plots that describe the retransmissions in the network.
They are last two graphs on the page. lqi30, lqi5, and lqi5b lines
extend beyond 30, 5, and 5 because of the bug I pointed out in the LQI
forwarding engine. The lines do not extend beyond 2x the max
transmissions (for example, 60, for lqi30) because of the low pkt
generation rate. If the pkt generation rate was high this line could
potentially extend to infinity. The shape of lqi30 retransmission is
interesting - we can guess (looking at the trend) that 20% of the
retransmission sequences used up the max retransmissions and probably
failed to deliver a packet to the next hop. CTP also shows a similar
(hitting the wall) feature near 30, which is also its max
retransmissions per parent. I think this graph is an evidence that the
links on CTP paths are generally better than the links on the LQI
paths. Looking at the retransmission count over time shows a steeper
curve in the beginning and flatter curve after some time. The time
distribution of various metrics we discussed in the past showed how
path metrics improved over time, but this retransmission count over
time shows how link qualities on the selected path improves over time
or better links are what constitute a path as experiments progress.
Cumulative retx count for lqi5b seems more or less linear.

I have added these two retransmissions graphs on the Mirage results as well:

http://enl.usc.edu/~om_p/net2/ctp4bitle/mirage-12242007/figures.html
http://enl.usc.edu/~om_p/net2/ctp4bitle/mirage-12212007/figures.html

- om_p