Referral properties
Applies To: Windows Server 2003 R2
The following options are available when you view the properties of a namespace root or folder with targets.
Amount of time clients cache referrals
When this option is available: Available when the DFS Management snap-in connects to a namespace server that is running a version of one of the following operating systems: Windows Server 2003 R2, Windows Server 2003 with Service Pack 1 (SP1), Windows Server 2003, and Windows 2000 Server.
Supported namespace types: Domain-based; stand-alone.
Supported namespace server operating systems: Windows Server 2003 and Windows 2000 Server.
Supported clients: All supported namespace clients.
Where configured: Namespace properties, Referrals tab; Folder properties, Referrals tab.
For clients that are not running Windows XP with Service Pack 2 (SP2) or Windows Server 2003 with SP1, the cache duration determines the earliest time that a client computer will request a new referral if the existing cached referral expires before it is accessed again. Clients that use a cached referral will renew the cache duration value of the referral each time a file or folder is accessed using the referral and, thus, use the referral indefinitely until the client’s referral cache is cleared or the client is restarted.
This behavior is different for clients running Windows XP with SP2 or Windows Server 2003 with SP1. Specifically, the cache duration is not renewed each time a client accesses a target using a cached referral. Instead, the referral expires after the cache duration value lapses.
One benefit of this change is that namespace clients running Windows XP with SP2 or Windows Server 2003 with SP1 will more quickly discover changes to namespaces and namespace folders. For example, if the folder targets of a folder named Current are changed daily, namespace clients without Windows XP with SP2 or Windows Server 2003 with SP1 would refresh the duration value each time they access the Current folder, causing them to continue to reference stale folder targets well beyond the duration value associated with the initial referral request.
To change the amount of time that clients cache referrals, see Change the amount of time that clients cache referrals.
Ordering methods for targets in referrals
When this option is available: Availablewhen the DFS Management snap-in connects to a namespace server that is running a version of one of the following operating systems: Windows Server 2003 R2 or Windows Server 2003 with SP1.
Supported namespace types: Domain-based; stand-alone.
Supported namespace server operating systems: Windows Server 2003; namespace servers running Windows 2000 Server cannot provide referrals based on lowest cost.
Supported clients: All supported namespace clients.
Where configured: Namespace properties, Referrals tab; Folder properties, Referrals tab.
When a client computer attempts to access a namespace, a domain controller or namespace server provides a referral to the client. The referral contains a list of target servers that are sorted according to the currently configured ordering method. When a client accesses the namespace root or a folder with targets in the namespace, the client attempts to access the first target at the top of the referral; the client moves to the next target if the prior target was not available.
The three ordering methods are:
Random order
In this method, targets are ordered as follows:
Targets in the same Active Directory site as the client are listed in random order at the top of the referral.
Next, targets outside of the client’s site are listed in random order.
If no same-site target servers are available, the client computer is referred to a random target server no matter how expensive the connection is or how distant the target is.
Lowest cost
In this method, targets are ordered as follows:
Targets in the same site as the client are listed in random order at the top of the referral.
Next, targets outside of the client’s site are listed in order of lowest cost to highest cost. Referrals with the same cost are grouped together and within each group the targets are listed in random order.
Note
Site link costs are not shown in the DFS Management snap-in. To view site link costs, use the Active Directory Sites and Services snap-in.
Exclude targets outside of the client's site
In this method, the referral contains only the targets that are in the same site as the client. These same-site targets are listed in random order. If no same-site targets exist, the client does not receive a referral and cannot access that portion of the namespace.
Note
Targets that have target priority set to "First among all targets" or "Last among all targets" are still listed in the referral, even if the ordering method is set to Exclude targets outside of the client's site.
To change the ordering method, see Set the ordering method for targets in referrals.
Clients failback to preferred targets
When this option is available: Availablewhen the DFS Management snap-in connects to a namespace server that is running a version of one of the following operating systems: Windows Server 2003 R2 or Windows Server 2003 with SP1.
Supported namespace types: Domain-based; stand-alone.
Supported namespace server operating systems: Windows Server 2003 with SP1.
Supported clients: Windows XP with SP2 and the Windows XP client failback hotfix; Windows Server 2003 with SP1 and the Windows Server 2003 client failback hotfix. These hotfixes are described in article 898900 in the Microsoft Knowledge Base on the Microsoft Web site (https://go.microsoft.com/fwlink/?LinkId=53202).
Where configured: Namespace properties, Referrals tab; Folder properties, Referrals tab.
Client failover in DFS Namespaces is the process in which a client attempts to access another target in a referral after one of the targets becomes unavailable due to a server or network failure, or due to the target being removed from the namespace. After failover, the client might access a non-optimal target, such as a target with a high site link cost with respect to the client, and the client will continue to access the remote server even after the local server is restored. If you want clients to fail back to a preferred local server when it is restored, select the Clients fail back to preferred targetscheck box.
Note
When a preferred local server is available, all new file accesses will be to the local server. Files that are currently open will be accessed from the non-preferred server until that file is closed.
To enable client failback, see Enable client failback.