At my current client they have been relatively slow on the uptake of Windows Server 2003 SP1, so those of us working within the Integration Services team have not had to deal with any complications that this service pack has introduced to BizTalk. Recently however we have been installing SP1 and have noticed a number of errors that have been introduced because of this.

We observed that BizTalk Host Instances were being stopped and restarted automatically. Following this up in the Windows Event Log we noticed a number of error messages relating to DBNETLIB and other entries indicating that there were issues relating to network connectivity. Some captures of these are shown below.

After some research we came across the following Knowledge Base article at Microsoft:;en-us;899599

Now the symptoms described in this article are exactly what we were experiencing. Apparently Windows SP1 introduces some extra security feature that reduces the size of the queue for concurrent TCP/IP connections to the server, which helps to prevent denial of service attacks.

All well and good, however the article suggests the actual issue only materialises when TCP/IP is under heavy load, sometimes incorrectly identifying valid TCP/IP connections as a denial of service attack. However, we have been receiving the errors when the BizTalk Group was under no load whatsoever.

After implementing the registry modifications in that article the problems did disappear, but I am interested why the BizTalk Group was experiencing the condition at all when there was no load. I spent some time investigating what may be the root cause and the only conclusion I could come to was that it may be related to the number of host instances that we had within the BizTalk Group; there were 40 in this case.

I have not had the time to investigate this any further, although a simple enough test would be to see whether the errors materialise with less host instances. One other thing that I did notice after installing Windows 2003 SP1 though was the number of security log entries. Is it just me or do we now see a huge increase in the number of entries? Something else I would like to investigate time permitting.

Just a final note, I have seen this occur with both BizTalk 2004 and BizTalk 2006.