Consider the following scenario:
You publish a web server and authenticate all requests in a Microsoft Forefront Threat Management Gateway (TMG) 2010 environment.
You set Authentication delegation to Kerberos constrained delegation (KCD).
You experience a network issue such as a loss of network connectivity, or the domain controller is restarted.
In this scenario, the connection to the domain controller is closed, and TMG 2010 never tries to reestablish the connection.
To resolve this problem, install the hotfix package that is described in the following Microsoft Knowledge Base article:
2735208 Rollup 3 for Forefront Threat Management Gateway (TMG) 2010 Service Pack 2
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
By default, TMG 2010 uses the "Domain NETBIOS name\User name" format when it requests a Kerberos ticket. Therefore, the domain name and the user name in the Kerberos ticket resemble the following:
Realm: MyCompanyUpdate 960146 introduced a design change to control the format of the domain name and the user name. This design change was made in Microsoft Internet Security and Acceleration (ISA) Server 2006 and is maintained in TMG 2010.
If a network issue is experienced, such as a network connectivity issue, or the domain controller is restarted, the connection with the domain controller is disconnected. Additionally, TMG never tries to establish the connection again. This may cause TMG to leave the user name and domain name unformatted.
For more information about the design change introduced in update 960146, click the following article number to go to the article in the Microsoft Knowledge Base:
960146 An update is available for ISA Server 2006 to control the domain name and user name format in Kerberos Constrained Delegation scenariosFor more information about software update terminology, click the following article number to go to the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates