Do you have a support agreement with Symantec.
If so, log a call and ask to run Appcritical between the Media server and the client, and then between the client and the media server (it only goes in one direction, hence why run twice).
If not, there is a free alterative to AppCritical, hopefully someone on here will know what it is called, as for the life of me, I can't remember.
the problem with this is, how many possible causes would you like :
Faultly hardware (including cables)
Drivers or Firmware (on any of the hardware involved (eg NIC card, switch)
Faulty ports on switch
Firewalls / Routers
OS settings (we have discussed some, did you try the ones I posted up ?)
** If you change them make a note of what they were, if the new setings don't fix, or improve, put them back else we could start introducing more faults that cause the same symptoms, which will be very very hard to sort out) **
I've even seen an error where the network card wouldn't send a particular type of data, all was ok until it hit a certain file, and just wouldn't send it ...think it was a .tar file, can't remember the fix though I think it was hardware related.
When the issue happens again, at the 'exact' time of failure - run netstat -a and attach the output to a file on this thread.
Did this client ever work, and if so, when did it stop working.
If so, on the day it stopped working, what was changed, bause it's 99.9% certain that something has - and this could be the key to finding the cause. Your customer is going to have to try and remember, because I really don't believe nothing changed.
If none of the above lead to anything then I can only think to get a tcpdump of the interface whist the backup is running and, until it fails, then look at it in wireshark (free) - and for that, you will really need to find a network type person who is used to looking at tcpdumps. From that, it should be possible to see why it fails, or at the very least narrow it down.
