Exchange 2003 post SP2 DSProxy Referral Update

By default, Outlook 2002 requests a global catalog referral from DSProxy. This strategy works well in many scenarios. Under some circumstances, however, you may want to configure the client to use a specific global catalog server. For example, the Outlook client and the Exchange server may be separated by a WAN (Figure 7).



Figure 7   WAN separating Outlook and Exchange server

In Figure 7, the Exchange 2000 topology is centralized with all Exchange 2000 servers located at the data center of the company. Users are located in branch offices, and log on to their mailboxes over the WAN. By default, Outlook receives a referral to either GC1 or GC2. This is because DSProxy identifies the global catalog servers that are closest to the



server running DSProxy, rather than the global catalog servers that are closest to the client. In this example, the Active Directory designers have chosen to implement a global catalog server at the branch office so that logon traffic is kept local.

Although the default referral works, you can optimize traffic patterns by configuring the following registry key so that the client uses the closest global catalog server.


Location
HKEY_CURRENT_USERSoftwareMicrosoftExchange
Exchange Provider

Name
closest GC

Type
REG_DWORD

Value
0x00000001




In other topologies, you may want to force Outlook to communicate with a specific global catalog server. Although you can manually change the registry parameter in the MAPI profile, it will be overridden the next time the client computer starts. To force Outlook 2002 to use a predefined global catalog and override settings in the MAPI profile, set the following special registry key.



Location
HKEY_CURRENT_USERSoftwareMicrosoftExchange
Exchange Provider

Name
DS Server

Type
REG_SZ (string)

Value
<FQDN of the global catalog server>




With either of the previous registry settings, if the specified global catalog server fails, Outlook will request a new referral from DSProxy. When configuring the client to select the global catalog server, you should remember the following:

·    The global catalog server chosen by the client may be out of date or may not be fully functional. If the global catalog server is having problems but still responds to NSPI requests, Outlook may not fail over to DSProxy for a new referral.

·    In multiple-domain environments, the global catalog server chosen by the client may not be in the same domain as Active Directory group objects. Therefore, users may not be able to update group membership, because the local global catalog server has a read-only copy of the group.