[Udpcast] Image does not complete correctly (receiver hangs)
bastiaans at sara.nl
Tue Jan 3 17:29:45 CET 2006
Alain Knaff wrote:
> What exactly is "new"? New make of network card? New switch? More than
> one switch between sender and receiver? Maybe even a router? Is it
> possibly for you to test each change "one-by-one", to try to identify
> which particular change brings the problem.
A extra networkcard in the server and 1 switch connected to it (for
testing) with 4 machines connected to it (for testing).
There are no routers between them.
> It looks like the "return" traffic (from the receiver back to the
> sender) is not working correctly. It's somewhat bizarre, because
> apparently it did work at the beginning of the transfer (or else the
> transfer could not have taken place at all, unless you used
> asynchronous mode)
Indeed weird, only at the end the problem seems to arise.
I am not running in asyncrhonous mode.
> From the IP addresses, I assume you are using unicast mode (one single
> It would help if you would tell us more about your network. What
> devices (switches, routers, etc.) are sitting between your sender and
> your receiver? What netmasks are involved? Where was the tcpdump
> observed (on sender? on receiver? on an unrelated box? If so, how was
> that box connected?) Are you reasonably sure that the trace is
> complete? (Many switches send unicast traffic only to the port where
> that machine is connected, unless you use a specifically configured
> monitoring port. That means that if you used an unrelated box to
> observe, the trace might be incomplete, depending on how the
> switch(es) has(ve) been set up)
Yes, I tried this particular case in unicast mode, to eliminate any
possible multicast issues that might arise.
I would figure a unicast setup should work, even if the switch has
problems with multicasting.
The network on networkcard X is a /22 network (255.255.252.0), the
network on networkcard Y is a /21 network (255.255.248.0).
The tcpdump was done on the sending side/image server, so I should be
able to see the return packets in the tcpdump (I see return packets
during transferring earlier on).
The setup pretty much looks like this right now:
server networkcard Y ->| switch |-> machine 1
|-> machine 2
|-> machine 3
|-> machine 4
There are really only three types of people:
Those who make things happen,
those who watch things happen,
and those who say, "What happened?"
ing. R. Bastiaans
HPC - Systems Programmer
SARA - Computing and Networking Services
Kruislaan 415 PO Box 194613
1098 SJ Amsterdam 1090 GP Amsterdam
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