perfsonar development work

["Jeff W. Boote" <>]

Stephan Kraft wrote:
> Hi Sven,
>
> our office is closed during holidays, so we haven´t a chance to answer
> your questions. Next week, we all will be back (or in Cambridge) to
> solve the problems.
>
> Hope Verena will answer them.


I can answer a couple of these questions...

> Sven Ubik schrieb:
> > Hi,
> >
> > tried bwctl installation at 
> > http://www.win-labor.dfn.de/bwctldemo/bwctl_demo.php
> >
> > and I have a few questions or notes:
> >
> > 1) What is difference between:
> >
> > "Buffer size (in byte) (Size of read/write buffer for udp)" and
> > "Window size (in byte) (Size of tcp window / udp socket receive buffer)"

Buffer size is the size of the 'user space' buffer that is read/written in the 
iperf application. This is for both TCP and UDP. (For UDP this also determines 
the packet size because it proscribes the full packet payload.)

Window size is really the max send/recv socket buffer size as set by setsockopt 
and SO_RCVBUF and SO_SNDBUF. And, it is not actually used for UDP - but I 
believe iperf still takes the -w option without complaint.

> > Window size does not have sense for UDP (which is mentioned on the second
> > line). And you can never set window size for TCP, it is a dynamic property
> > of TCP protocol. You can only set the upper limit of socket buffers, which
> > then determine the upper limit of window size.
> >
> > On the other hand, you can also set the volume of data sent by the
> > application at once, which can affect resulting throughput.
> >
> > Is the above mentioned "buffer size" what you set by sysctl or
> > setsockopt() or the resulting real buffer size after internal adjustments
> > in Linux kernel (which also depends whether it is 2.4 or 2.6)?
> >
> > What are default values?

The default Buffer size in bwctl/iperf is:

TCP: 8 KB
UDP: 1470 bytes

The default Window size is per-system tunable using sysctl. The actual used 
value that was used is in the iperf/bwctl output data. (But, I don't know if 
that is exposed by this web service.)

Sorry, I can't help with the rest of the questions - they are specific to the 
DFN deployment. (VV - let me know if it looks like any of these problems are due 
to bwctl bugs. I would be happy to try and fix them. Along those lines, there is 
a bug in the current released version that makes the 'fuzzfactor' option not 
work correctly, so if these hosts are not properly synced with ntp that could be 
at least part of the problem.)

jeff

> > 2) I tried first:
> >
> > Prague IPv4 -> Amsterdam IPv4 and I got:
> >
> > BWCTL Error: bwctl: Unable to connect to 192.87.102.210: Connection
> > refused
> >
> > then I tried Paris -> Athens and I got:
> >
> > BWCTL Error: bwctl: Unable to connect to 194.177.210.70: Connection
> > refused
> >
> > then I tried Paris -> Rome and I got:
> >
> > BWCTL Error: RECEIVER START RECEIVER END
> >
> > then I tried Sofia -> Zagreb and I got:
> >
> > BWCTL Error: bwctl: Unable to connect to 193.198.229.166: Connection
> > refused
> >
> > then I tried Amsterdam ->  Athens for UDP (previous tests were for TCP)
> > and I got:
> >
> > SOAP error:
> > HTTP Error: Couldn't open socket connection to server
> > http://192.87.102.210:8090/, Error (111): Connection refused
> >
> > then I tried Gent -> Ljubjjana for UDP and I got:
> >
> > BWCTL Error: RECEIVER START 3376807663.317963: iperf -B 193.2.63.2 -P 1 -s
> > -f b -m -p 5001 -u -t 10
> >
> > I did not find any combination that works.
> >
> > 3) When I do one measurement and go back to do another measurement, all
> > items in the form are lost and I have to fill in everything again. Is it
> > possible to remember the latest values?
> >
> > 4) When I find that throughput was low between some two points, do I get
> > any feedback, that allows me to determine why it was low?
> >
> > Regards,
> >
> > Sven