Although the walkthrough doesn't specify waiting, it is a race
condition that we occasionally hit in tests. Adding a 2 second
delay seems realistic (for when a human is doing the walkthrough)
and should reduce the likelihood of hitting the race condition.
than CPU-limited, which should expose the feature we are trying
to demonstrate (TCP data rate slowing down as latency increases
due to congestion control.)
Without waiting for mn to exit, OVS keeps listening on the
static listening port, which prevents UserSwitch from listening
on it (and starting up) in the next test.
For some time, UserSwitch has suffered from abysmal performance due
to rx and tx offload settings. In the latest Ubuntu 16.04/Linux 4.4
kernel, it simply doesn't work with the default settings, since
packets with bad TCP checksums are generated at one end, passed through
the user switch, and dropped at the other. It doesn't seem to be
something we can fix in UserSwitch itself although it may be possible
to do something in the C code of the Stanford reference switch and
CPqD switch.
Previously the standard OpenFlow poort (6653) that Controller()
may be listening at would conflict with the default listenPort
for switch 20 (usually UserSwitch 20), breaking waitConnected()
and disconnecting that switch from the network in general.
Fixes#668
It's very useful to be able to pass parameters to tests.
Unfortunately, our previous --test argument syntax didn't
permit it, because , was used as a delimiter for multiple
tests. With this change, we change , to become a delimiter
for arguments, as it is with other options to mn. For now,
we introduce + as a separator, as it is legal in filenames
and therefore shouldn't conflict with special characters
used by Unix shells.
We also reorganize mn a bit to make it hopefully slightly
clearer.
Unfortunately pexpect() seems to be timing out with a 30 second
timeout rather than the 600 seconds we are passing in. How
could this even be working normally? It is puzzling. We are
going to try specifying the timeout in the spawn() call.
Also if the test fails, we use %e format for readability.
With a 1 ms delay, the performance tests periodically fails
under nested virtualization, which is how we are testing it.
Increasing the delay should make the effect (lower TCP
data rates as latency increases, due to TCP's congestion
control algorithm) more pronounced and robust.
If we want to observe a monotonic affect, we should
make sure that we are in fact CPU limited where it
matters. In this case, we are CPU limiting the hosts,
and the iperf client uses a lot of CPU. We need to
reduce the CPU allocation so that iperf is in fact
CPU bound.
We also correct the CPU allocation so that the client
and server each receive 50% of the total. Previously
we were specifying the per-host CPU allocation, so
45% meant we were allocating 90% of the overall CPU,
which seems a bit confusing. On the other hand, now
at 40% each host gets 20% of the CPU, which could also
be considered slightly confusing!
Although the client transmit rate is going to be the
limiting factor, we still measure the received data
rate at the server, because that is more interesting
than the initial burst of buffering at the client.
Measuring at the server becomes more important as
we reduce the iperf time.
The output is also changed slightly, and the test has
been updated appropriately.
Although we could use print() from __future__, this messes
up scripts which use examples as modules.
The simple, if not nicest for 2.7, solution is to use
info(), output() and other mininet.log functions. The disadvantage
is that we may have to adjust things if we change info() to
add automatic newlines, but we can burn that bridge in Mininet
3.x.
Presumably daemons, race conditions, or ephemeral processes
can cause the ps output to vary slightly. We allow up to
two differing lines to account for this.
Fixes#651
The version string changed in tshark 2.0.2 in Ubuntu 16.
Perhaps we should just check for the version string itself
to be more robust but this is probably OK for now.
Brian O'Connor
Brian O'Connor
lantz
Niels van Adrichem
Felix Konstantin Maurer
Nirmoy Das
vik_y
Jon Hall