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If you utilise Microsoft Internet Information Services IIS or an application that uses the System.Net.HttpListener class is installed or running on one the operating systems below, and you have a Network Load Balancer then you may find that Increased latency occurs on HTTP and HTTPS requests and traffic.

This issue occurs because the HTTP and HTTPS requests from clients can include zero length data in the SSL records, certain server-side variables do not update correctly in this instance and Http.sys leaves the connection in the CLOSE_WAIT state. This intern exhausts the open connection limit can introduce latency, timeouts and connection problems.

Affected Operating Systems:

Microsoft Windows Vista

Microsoft Windows 7

Microsoft Windows Server 2008

Microsoft Small Business Server 2008 – SBS 2008

Microsoft Windows Server 2008 R2

Microsoft Small Business Server 2011 – SBS 2011

The Microsoft Knowledge Base Article KB 2634328 includes further information on this issue and provides an updated version of Http.sys that corrects the issue http://support.microsoft.com/kb/2634328

32 bit applications that utilise NetBIOS API do not receive connection close notifications in Windows 7 64 Bit Edition, Windows Server 2008 R2 or Windows Small Business Server 2011 and as a result they do not try to re-establish a session. Restarting the application will re-establish the session and recover from the issue.

This issue occurs because when the Netbios.sys driver receives data the driver does not convert the Network Connection Block NCB structure from 64 bit to 32 bit when the session has been dropped. A 32 bit application cannot understand the 64 bit NCB structure which is why the session cannot be re-established.

The Microsoft Knowledgebase article KB 2633667 provides further information on the issue and a Hotfix containing an updated version of the Netbios.sys driver that that corrects this particular issue http://support.microsoft.com/kb/2633667

Microsoft Windows 7 or Windows Server 2008 R2 – BITS client will reset the TCP connection each time is downloads a range of the file and increases overall network traffic.

You can find more information and the download link for a hotfix that addresses the issue in Microsoft KB 2654875 http://support.microsoft.com/kb/2654875

Microsoft Windows Server 2008 and Microsoft Windows Server 2008 R2 DNS Server may stop responding to DNS queries and requests from client computers, this issue may occur randomly and when it is occuring the DNS Server stops responding.

This issue occurs because the DNS Server goes into an infinite loop, more information about this issue and a hotfix to address the issue is provided in Microsoft KB 2655960 http://support.microsoft.com/kb/2655960

HTTP and HTTPS requests or traffic to a Windows Vista, Windows 7, Windows Server 2008, SBS 2008, Windows Server 2008 R2 or SBS 2011 machine may exhibit increased latency if the connection is through a network load balancer

32 Bit Applications that utilise NetBIOS API do not receive connection close notifications in Windows 7 64 Bit Edition, Windows Server 2008 R2 or Windows Small Business Server 2011

Microsoft Windows 7 or Windows Server 2008 R2 – BITS client will reset the TCP connection each time is downloads a range of the file and increases overall network traffic

Microsoft Windows Server 2008 and Microsoft Windows Server 2008 R2 DNS Server may stop responding to DNS queries and requests from client computers

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