Configure the Availability Service for Cross-Forest Topologies

Applies to: Exchange Server 2010

The Availability service improves information workers' free/busy information by providing secure, consistent, and up-to-date free/busy information to clients that are running Microsoft Office Outlook 2007. By default, this service is installed with Microsoft Exchange Server 2010. In cross-forest topologies where all connecting clients are running Outlook 2007, the Availability service is the only method of retrieving free/busy information. You can use the Shell to configure the Availability service for cross-forest topologies.

Looking for other management tasks related to the Availability service? Check out Managing the Availability Service.

Using the Availability Service in Trusted and Untrusted Forests

You can use the Availability service in cross-forest topologies across trusted or untrusted forests. The type of free/busy information that's available depends on if you're using a trusted or untrusted forest.

Trusted Forests   In trusted forests, you can configure the Availability service to retrieve free/busy information on a per-user basis. When the Availability service is configured to retrieve free/busy information on a per-user basis, the service can make cross-forest requests on behalf of a particular user. This allows a user in a remote forest to retrieve detailed free/busy information for someone who is not in the same forest.

Untrusted Forests   In untrusted forests, you can only configure the Availability service to retrieve free/busy information on an organization-wide basis. When the Availability service makes free/busy cross-forest requests at the organizational level, free/busy information is returned for each user in the organization. In untrusted forests, it isn't possible to control the level of free/busy information that's returned on a per-user basis.

Configuring Windows for Cross-Forest Topologies

To configure Microsoft Windows for a cross-forest topology, you must install and configure GAL Synchronization (GALSync). For information about how to install and configure the GALSync feature in Microsoft Identity Integration Server (MIIS), see the following resources:

• Microsoft Identity Integration Server 2003 Scenarios
• Microsoft Identity Integration Server 2003

If you're running Office Outlook 2003 or an earlier version, you must use the Microsoft Exchange Inter-Organization Replication tool to synchronize free/busy information across multiple forests. For more information about the Microsoft Exchange Inter-Organization Replication tool, see Microsoft Exchange Server Inter-Organization Replication.

Use the Shell to configure per-user free/busy information in a trusted cross-forest topology

You need to be assigned permissions before you can perform this procedure. To see what permissions you need, see the "Availability Service Permissions" entries in the Client Access Permissions topic.

This example configures the Availability service to retrieve per-user free/busy information on a Client Access server in the target forest.

Get-ClientAccessServer | Add-ADPermission -Accessrights Extendedright -Extendedrights "ms-Exch-
EPI-Token-Serialization"  -User "<Remote Forest Domain>\Client Access servers"

This example defines the free/busy access method that the Availability service uses on the local Client Access server in the source forest. The local Client Access server is configured to access free/busy information from the forest ContosoForest.com on a per-user basis. This example uses the service account to retrieve free/busy information.

Add-AvailabilityAddressSpace -Forestname ContosoForest.com -AccessMethod PerUserFB -UseServiceAccount:$true

If you choose to configure cross-forest availability with trust, and also choose to use a service account (instead of specifying organization-wide or per-user credentials), you must extend permissions as shown in the example in the "Use the Shell to configure trusted cross-forest availability with a service account" section. Performing that procedure in the target forest gives Client Access servers in the source forest permission to serialize the original user context.

Use the Shell to configure trusted cross-forest availability with a service account

You need to be assigned permissions before you can perform this procedure. To see what permissions you need, see the "Availability Service Permissions" entries in the Client Access Permissions topic.

This example configures trusted cross-forest availability with a service account.

Get-ClientAccessServer | Add-ADPermission -Accessrights Extendedright -Extendedright "ms-Exch-EPI-Token-Serialization"  -User "<Remote Forest Domain>\Exchange servers"

For detailed information about syntax and parameters, see the following topics:

• Get-ClientAccessServer
• Add-ADPermission
• Add-AvailabilityAddressSpace
• Set-AvailabilityConfig

Use the Shell to configure organization-wide free/busy information in an untrusted cross-forest topology

You need to be assigned permissions before you can perform this procedure. To see what permissions you need, see the "Availability Service Permissions" entries in the Client Access Permissions topic.

This example sets the organization-wide account on the availability configuration object to configure the access level for free/busy information in the target forest.

Set-AvailabilityConfig -OrgWideAccount "Contoso.com\User"

1. This example adds the Availability address space configuration object for the source forest.

$a = get-credential  (Enter the credentials for organization-wide user in Contoso.com domain)
Add-AvailabilityAddressspace -Forestname Contoso.com -Accessmethod OrgWideFB -Credential:$a

Configuring Cross-Forest Availability in Forests that Include Exchange 2003

For Outlook 2007 and Exchange 2010 users to view the free/busy information of Exchange Server 2003 users in another forest, you must configure the Availability service by using the Add-AvailabilityAddressSpace cmdlet.

You only have to run this command once on any server in the Exchange 2010 forest. You can run this cmdlet from any computer running Exchange 2007 or Exchange 2010.

Use the Shell to configure cross-forest availability in forests that include Exchange 2003

You need to be assigned permissions before you can perform this procedure. To see what permissions you need, see the "Availability Service Permissions" entries in the Client Access Permissions topic.

This example sets public folder free/busy availability.

Add-AvailabilityAddressSpace -ForestName Contoso.com -AccessMethod PublicFolder

Other Tasks

After you configure the Availability service for cross-forest topologies, you may also want to:

• Diagnose Availability Service Issues
• Configure the Availability Service for Network Load Balanced Computers