Maximum concurrent connections to a Microsoft NLB Cluster

We recently had a problem with maximum conncurrent connections on a Microsoft NLB cluster, that I got an answer to on stackoverflow:

http://stackoverflow.com/questions/909677/iis-6-0-server-too-busy-http-503-connectiondropped-defaultapppool

What I was wondering in addition was:

• Is there a limit of 65,534 concurrent connections?
• Is this limit per server, network card or NLB cluster?
  • Could we increase the number of concurrent connections by adding network cards to the servers?
• Is this a limit in Microsoft technology or is it in the TCP/IP protocol?

Thanks

Shiraz

EDIT

Just to clarify: Even though all clients are calling the cluster IP address, the number of connections possible will be dependent upon the number of individual IP addresses in the cluster?

You are running Server2003, but it still an interesting read even if it applies to Server 2008.

http://support.microsoft.com/kb/951764
http://msdn2.microsoft.com/en-us/library/cc150670(VS.85).aspx

…and since 2008 takes care of this issue and to answer your questions,

• Yes

• Per IP address (adding network interfaces would increase the number of IP addresses, so it seems reasonable that this would solve it).

• This looks like a TCP/IP limitation especially since adding IP addresses “fixes” it.

Check more discussion of this question.