Question : Concurrent NetBios (SMB) requests over a NAT Firewall?

Hi,

I have the following problem:

a win32 client application needs file-level access to a UNC share (e.g. '\\server\fileshare') located in a network segment only accessible via a NAT firewall (that is, all connections to this UNC share go over the NAT).

Having configured the firewall to allow NetBios traffic (TCP port 139), I have managed to get the application to run satisfactorily.
 
However, as soon as two clients are up and performing any sort of File I/O on this share (not on the same file or even in the same directory necessarily), one of the clients chokes up.

I have tested this on OS-level by simply mounting the share as a network drive and interacting with it and even here I have difficulties as soon as I try doing concurrent accesses from multiple systems behind the NAT.

I have configured numerous protocols (MS-SQL, mysql, http, etc.) to pass through the NAT without difficulty. What is the difference with NetBIOS/SMB?

Is there any way to get concurrency over the NAT and if so, how?

BTW, The situation is reproducible with a number of different NAT firewalls, specifically the ISA Server from Microsoft and some ipchains variant running on linux/bsd (it is off-site and I don't have the exact details) seem to have this trouble.

Any information regarding this situation would definitely make my day.

Many thanks and best regards,
--chris



Answer : Concurrent NetBios (SMB) requests over a NAT Firewall?

This was the first hit I got from the MS site - is this it?

http://support.microsoft.com/default.aspx?scid=kb;en-us;301673
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