[Testbed-admins] Event system questions

["Manuel Requena" <mrequena@cttc.es>]

Hi,

I'm testing traffic generation and event system following the "Emulab
Tutorial - A more advanced example" and I have found some issues. I set a
simple scenario with 2 nodes and 1 UDP data flow with some "at" commands.

When I swap in or modify an experiment, the events are not scheduled. I know
it because I launch some "tcpdump" in the nodes. Are there some log files to
see when the events are scheduled? I don't see my UDP packets (every 5ms
during 20 secs with a length of 500 bytes). But in the first 2 secs and
every 10ms, I see some UDP packets (not mine ones) of 62 bytes (ethernet
length) between the 2 nodes. What are these packets?

If I "Replay Events" in the web interface, I can see my UDP packets. What I
have forgotten in order to launch the events when an experiment is created /
swapped in?

Moreover, I have some general questions:

- How the nodes are synchronized? What precision you can get? "Emulab nodes
are kept in sync with NTP", but where the NTP server is? boss? ops? When
nodes boot I get the following:

"Starting ntpd.

Oct  1 07:29:09 tbsdelay0 ntpdate[1021]: no server suitable for
synchronization found

WARNING: ntpdate failed!"

So I guess my nodes are not synchronized. What I have to modify? Nodes
configuration? Some tables? Emulab software installation?

- In the "at" command, how the "0.0 time" is specified? When I "Replay
events", I guess that the "0.0 time" is more or less when I select the
option in the web interface. Could I specify the "0.0 time" at 13:15, for
example, and the rest of the "+XX" events are scheduled accordingly?

Best regards,
Manuel