The Exchange 2000 ADC plays an important role in Exchange 5.5 and Active Directory coexistence. It synchronizes directory objects between Exchange 5.5 and Active Directory. This enables organizations that have maintained an attribute rich Exchange 5.5 directory to bring that data across to their Active Directory and keep it synchronized.

During synchronization, the ADC matches Exchange 5.5 objects with equivalent Active Directory objects: Exchange 5.5 mailboxes are equivalent to Active Directory users; Exchange 5.5 custom recipients, to Active Directory mail-enabled contacts; and Exchange 5.5 distribution lists, to Active Directory groups.

	Figure 3 Replicate and Synchronize. Click here.

There are two versions of the ADC: a Windows 2000 version and an Exchange 2000 version. The Windows 2000 version only synchronizes mail recipient objects and you can use it to populate Active Directory and centralize administration of the two directories. The Exchange 2000 version also synchronizes configuration objects between the two directories. This is required for coexistence between Exchange 5.5 and Exchange 2000. The Exchange 5.5 sites' configuration objects are synchronized to Active Directory to provide Exchange 2000 Servers with knowledge of the sites, servers, and other configuration objects necessary to coexist. And the Exchange 2000 setup won't allow an Exchange 2000 Server to join an Exchange 5.5 site if the Exchange 2000 version of the ADC isn't installed in the enterprise.

Figure 4 Upgrade Windows NT. Click here.

The ADC associates portions of each directory with connection agreements. Connection agreements are established between Exchange 5.5 sites and Active Directory domains to define which objects from each directory should be synchronized and where this should happen. A container in the Exchange directory, such as a recipient container, is associated with a container in the Active Directory domain, such as an organizational unit. The objects in these containers are synchronized based on the schedule defined in the connection agreement.

Synchronization occurs using Lightweight Directory Access Protocol (LDAP) between an Exchange 5.5 server, a Windows 2000 Server running ADC, and an Exchange 2000 domain controller configured as a Global Catalog server. If you plan to run Exchange 5.5 on a Windows 2000 domain controller, you must change the Exchange LDAP port to something other than port 389, the one Windows 2000 uses.

Both the Windows 2000 and Exchange 2000 ADC versions have connection agreements that synchronize mail-enabled objects between directories. It's important to define where ADC connection agreements are needed in your environment before implementing the ADC.

Configuration can be more complex. You can configure the connection agreement for one-way synchronization, in either direction, or for two-way synchronization, based on your requirements. One-way synchronizations will only write changes to the directory in one direction. It's also possible to configure the types of objects a connection agreement will synchronize (see Figure 1).

To add to the complexity, you should define at least one connection agreement per site and domain as the primary connection agreement. This agreement creates new objects in the destination directory if those objects don't exist. Although it's not required, it's recommended you define only one primary connection agreement for each site and domain to avoid creating duplicate objects in the forest (see Figure 2).

	Figure 5 Move Users with ADMT. Click here.

In multisite and multidomain environments, you should take care to ensure objects are synchronized as needed. Where you define your connection agreements and which ones you designate as primary connection agreements depends partly on the ultimate location of your user accounts. It's important to fully understand the ADC and how you can use it in different environments; you'll quickly realize that the ADC and its configuration can be quite complex—so you'll need to plan for it and deploy it carefully.

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