[Udpcast] Image does not complete correctly (receiver hangs)

Ramon Bastiaans bastiaans at sara.nl
Tue Jan 3 16:45:16 CET 2006

Hi all,

I have been using udpcast to image machines succesfully for a while now.
Now we are expanding our infrastructure with more machines and extra 
networks, which I would like to image with the same server.

This seems to work a little, except for the fact that it does not 
complete correctly on the new network(card/interface).

The receiver seems to get allmost all data, but the udp-receiver seems 
to 'hang' at the end.
The most frustrating part is the udp-sender that says "Transfer 
complete, disconnecting".

When I try it in unicast and sniff the network I see the following on a 
_succesfull_ image to networkcard X:
16:06:59.620836 IP > UDP, length: 
16:06:59.620841 IP > UDP, length: 
16:06:59.620846 IP > UDP, length: 
16:06:59.620851 IP > UDP, length: 
16:06:59.620856 IP > UDP, length: 144
16:06:59.621146 IP > UDP, length: 8
16:06:59.621198 IP > UDP, length: 144
16:06:59.621397 IP > UDP, length: 8
16:07:00.654842 IP > UDP, length: 28
16:07:01.146772 IP > UDP, length: 4

When I do the same (failing) image to networkcard Y:
15:27:13.413078 IP > UDP, 
length: 1472
15:27:13.413084 IP > UDP, 
length: 1472
15:27:13.413089 IP > UDP, 
length: 1472
15:27:13.413095 IP > UDP, 
length: 1472
15:27:13.481157 IP > UDP, 
length: 144

And then nothing.
This is the last part of the imaging process, right up till it completes 
at networkcard X, and just hangs on networkcard Y.

It seems to me the last few packets are missing and that's causing the hang.

Anyone experienced something like this before and/or has any pointers to 
what might cause this?
I suspect a switch or similar device to block the last packets. I.e. a 
rate limiting setting or something.

Kind regards,
- Ramon Bastiaans.

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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