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This chapter is from the book

This chapter is from the book

Connection Agreement Properties

Although the Connection Agreement Wizard does a lot to simplify the creation of CAs, you'll find it useful to get familiar with the properties of the various types of CAs. You might need to modify the settings of a CA created by the CA Wizard. Or you might need to create a custom CA without the help of the wizard. You might also need to troubleshoot the operation of a CA, and that can get very tedious if you don't know how they operate with various settings.

Recipient Connection Agreements

Open the Properties window for one of the User CAs created by the wizard. Figure 12.30 shows the General tab.

12fig30.gifFigure 12.30 Connection Agreement properties showing the agreement type and the name of the ADC server.migration from legacy ExchangeCA propertiesrecipientsCAs (Connection Agreements)propertiesrecipient CAsRecipient Connection Agreements

The wizard creates two-way connection agreements, meaning that changes made to either directory service replicate to the other service. This ensures that you have full synchronization throughout the migration.

These settings are stored in Active Directory, so if you want another ADC server to take over the replication duties, you can select a different server using the Select a Server to Run option.

Connection Settings

Select the Connections tab, shown in Figure 12.31. This tab allows you to select the endpoint server for each side of the Connection Agreement and the credentials used to access the directory service on that server.

12fig31.gifFigure 12.31 Connections tab showing the two-endpoint servers in the Connection Agreement and the credentials used to make the connection.legacy Exchange serversmigration to Exchange 2003CA properties

If you decommission the legacy Exchange server acting as the endpoint to the Connection Agreement, use this tab to specify another legacy server. As you'll see in the next section, Exchange 2003 has a service called the Site Replication Service that maintains a replica of the legacy Exchange directory service on an Exchange 2003 server. You can point a CA at this SRS service rather than at a legacy Exchange server. The only caveat is that SRS listens at TCP port 379 rather than TCP port 389, the standard LDAP port.

If you change the password on either of the accounts used to access Active Directory or legacy Exchange, use this tab to change the passwords stored in the Connection Agreement. Failure to do so will be reported to the Application event log.

Schedule Settings

Select the Schedule tab, shown in Figure 12.32. The default setting for CA replication is Always. This replicates a change as it occurs.

12fig32.gifFigure 12.32 Schedule tab permits throttling back on replication to accommodate network restrictions, if any.

If immediate replication overloads a slow connection, you can elect to replicate periodically, such as hourly or every 15 minutes throughout a given window. Under general circumstances, you won't change the default setting.

"From Exchange" Settings

Select the From Exchange tab, shown in Figure 12.33. Note that the CA replicates all changes from a given legacy site into the staging area OU you created in Active Directory. You should only see Universal Distribution Groups, contacts, and disabled user accounts for resource mailboxes in this OU. The ADC locates a user object in the OU where it resides.

12fig33.gifFigure 12.33 From Exchange shows the source, target containers, and the object types that will be copied from legacy Exchange to Active Directory.migration from legacy ExchangeCA propertiesrecipientsCAs (Connection Agreements)propertiesrecipient CAsRecipient Connection Agreementslegacy Exchange serversmigration to Exchange 2003CA properties

"From Windows" Settings

Select the From Windows tab, shown in Figure 12.34. This side of the CA works a little differently. The CA takes changes made to mail-enabled objects anywhere in the domain and replicates them to objects in the legacy site container.

12fig34.gifFigure 12.34 From Windows specifies the source and target containers for the Connection Agreement, but does not indicate the type of objects. This is determined by a custom filter that cannot be seen in the user interface.migration from legacy ExchangeCA propertiesrecipientsCAs (Connection Agreements)propertiesrecipient CAsRecipient Connection Agreementslegacy Exchange serversmigration to Exchange 2003CA properties

If you think about it for a moment, this configuration might cause a problem. After all, the CA wizard creates several CAs, one for each legacy site. Each of these CAs pulls changes from the entire domain. This could lead to a situation where you mail-enabled an object in Active Directory, and the overlapping CAs each created a corresponding object in its own legacy site OU.

To avoid this, Microsoft does a little magic trick. In the From Windows tab, take a look at the Objects field. The ADC uses this field to configure a filter in the Connection Agreement to search only for objects of the specified class. If you were to configure a CA manually and check each of the object types, the ADC would create a filter to search for all objects of the User, Group, and Contact class.

Notice in the Connection Agreement created by the CA Wizard that the Objects field contains a gray background, and none of the checkboxes have checks. Instead of using a standard filter, the CA Wizard inserts a custom filter into the CA that limits the search to objects in the same site as the Exchange server that forms the endpoint of the Connection Agreement. This search restriction prevents overlapping CAs from creating multiple objects in their own site OU based on a single mail-enabled Active Directory object.

Just in case you're interested in the full details, here's how the custom filter created by the CA Wizard works. It's good to know this information if you ever want to create a CA without the aid of the CA Wizard.

Each mail-enabled object in Active Directory has an attribute called LegacyExchangeDN. As you might expect, this attribute corresponds to the Distinguished Name of the object in the legacy Exchange directory service.

The syntax of the LegacyExchangeDN attribute uses X.821 format rather than X.500 format, so an example would look like this: /o=Company/ou=Phoenix/cn=phoenixuser100.

When a user gets a mailbox, the Exchange Task Wizard determines the site of the user's home server and constructs a LegacyExchangeDN entry that corresponds to that site. For example, if you were to take a user with the logon name sydneyuser50 and give that user a mailbox on an Exchange server in Sydney, the LegacyExchangeDN attribute would look like this: /o=Company/ou=Sydney/cn=sydneyuser50.

When the CA Wizard creates a Connection Agreement, the wizard modifies the Active Directory search filter in the CA to look only for objects with a legacyExchangeDN that specifies the same site as the Exchange server acting as the endpoint of the CA. For example, if the Exchange server resides in the Phoenix site, then the CA search filter would look for LegacyExchangeDN entries equal to /o=Company/ou=Phoenix/cn=*.

Advanced Settings

Select the Advanced tab, shown in Figure 12.35. The wizard configured the CA as a Primary CA for the Windows domain but not for the Exchange organization. Only a Primary CA can create new objects or delete existing objects. By preventing the CA from creating new objects in the legacy Exchange directory service, you avoid potential update loops in which changes to the same object would replicate back and forth between multiple sites.

12fig35.gifFigure 12.35 Advanced tab shows that each CA is a Primary only on the Windows side and that an unmatched mailbox in legacy Exchange will create a disabled user account.legacy Exchange serversmigration to Exchange 2003CA propertieslegacy Exchange serversmigration to Exchange 2003CA propertiesmigration from legacy ExchangeCA propertiesrecipientsCAs (Connection Agreements)propertiesrecipient CAsRecipient Connection Agreements

The Advanced properties also tell the CA to create a disabled user account in Active Directory if it cannot match a mailbox owner to an Active Directory user. The other options include creating a new user object or a new contact object. These options have only limited utility, and you should not select them unless instructed by Microsoft Product Support Services in the event that you require their help to resolve a problem.

The Paged Results entry defines how many items the ADC will obtain in a single LDAP query. In Exchange 2003, Microsoft recommends leaving this setting at the default of 20 unless specifically instructed to use a higher number by a support technician or Microsoft consulting engineer. (The Exchange 2000 ADC Deployment Guide recommends raising this value to 99, but that does not apply to Exchange 2003.)

Deletion Settings

Select the Deletion tab, shown in Figure 12.36. The default configuration deletes objects in one directory service when the corresponding object gets deleted from the other directory service.

12fig36.gifFigure 12.36 Deletion tab shows that deleted objects in each directory service will cause action on the part of the other directory service, by default. The alternative is to save the action in a flat file for later application.legacy Exchange serversmigration to Exchange 2003CA propertieslegacy Exchange serversmigration to Exchange 2003CA propertiesmigration from legacy ExchangeCA propertiesrecipientsCAs (Connection Agreements)propertiesrecipient CAsRecipient Connection Agreements

Replicating object deletions between the two directory services can get a little complex, depending upon the object type and directory service from where you delete it.

Object Deletions Originating in Active Directory

If you delete a mailbox-enabled user, a mail-enabled group, or a contact in Active Directory, the object doesn't actually get deleted. Instead, the system strips off all but the most essential attributes, moves the object to a hidden container called Deleted Objects, and sets an attribute on the object called IsDeleted to TRUE.

The search criteria on the Connection Agreements created by the CA Wizard include a filter to look for objects with the IsDeleted attribute set to TRUE. When the ADC finds such an object, it instructs the legacy Exchange directory service to delete the corresponding object.

Mail Attribute Deletions Originating in Active Directory

If you use the Exchange Task Wizard in Active Directory Users and Computers to revert a mailbox-enabled user, a mail-enabled group, or a contact back to a standard object (the task name is Remove Exchange Attributes), the wizard strips most of the e-mail attributes from the object and then sets the value for the LegacyExchangeDN attribute to ADCDisabledMail.

The search criteria on the Connection Agreements created by the CA Wizard include a filter to look for objects that have the LegacyExchangeDN attribute set to ADCDisabledMail. When the ADC finds such an object, it instructs the legacy Exchange directory service to delete the corresponding object.

Object Deletions Originating in Legacy Exchange

On the legacy Exchange side, the action varies depending on whether the mailbox belongs to a real user or a disabled user linked to a resource mailbox.

  • If you delete a resource mailbox, the ADC deletes the corresponding disabled user object in Active Directory.

  • If you delete a standard mailbox, the ADC strips the e-mail attributes from the corresponding Active Directory object and sets the LegacyExchangeDN attribute to ADCDisabledMailByADC.

The search criteria on Connection Agreements created by the CA Wizard include a filter to look for objects that have the LegacyExchangeDN attribute set to ADCDisabledMailByADC. When the ADC finds such an object, it turns right around and attempts to delete the corresponding object from legacy Exchange, even though the object is already gone. This might seem redundant, but that's what happens.

Points to Remember about Object Deletions and the ADC

Here's a quick synopsis of the way the ADC handles object and attribute deletions:

  • If you delete a mailbox-enabled user in Active Directory, the ADC deletes the corresponding mailbox in legacy Exchange.

  • If you delete a mail-enabled group or contact in Active Directory, the ADC deletes the corresponding distribution list or custom recipient in legacy Exchange.

  • If you remove the e-mail attributes from users, groups, or contacts in Active Directory, the ADC deletes the corresponding mailbox, distribution list, or custom recipient in legacy Exchange.

  • If you delete a mailbox in legacy Exchange, the ADC strips the e-mail attributes from the corresponding user object in Active Directory.

  • If you delete a distribution list or custom recipient in legacy Exchange, the ADC strips the e-mail attributes from the corresponding group or contact in Active Directory.

Configuration Connection Agreements

Consider the legacy Exchange directory service replication topology diagrammed in Figure 12.37. Within each site, the Exchange servers send directory service updates directly to each other using Remote Procedure Calls (RPCs). Between sites, the bridgehead servers convert the directory service updates into messages that they send to other bridgeheads. When you start the migration to Exchange 2003, you introduce a new actor: the ADC server. You've already seen how the Connection Agreements created by the ADC keep recipients and public folders in sync between legacy Exchange and Active Directory. But that's not the whole story.

12fig37.gifFigure 12.37 Configuration Connection Agreement connects the legacy Configuration containers in each site with the Exchange Organization container in Active Directory.migration from legacy ExchangeCA propertiesconfigurationCAs (Connection Agreements)propertiesconfiguration CAsConfiguration Connection Agreements

Exchange 5.x stores server information in a Configuration container in the legacy Exchange directory service. Each Exchange server in a site knows about the other servers in the site by looking in this Configuration container. The legacy servers in a site won't know that you installed an Exchange 2003 server until they see the server's information in the legacy Configuration container. That's the job of the Configuration Connection Agreement, which is created automatically when you install the first Exchange 2003 server in the site.

Configuration CA Function

When you install an Exchange 2003 server, Setup creates objects under the Exchange organization container in Active Directory that represent the following functions:

  • Exchange server itself, including its operational settings

  • Site addressing

  • Connectors

  • MTA and transport protocols

  • Private and public mailbox storage parameters

  • Recipient Policies

  • Site (Administrative Group) configuration parameters

  • Encryption and secure messaging parameters

The ADC synchronizes these objects with the legacy Exchange Configuration container using a Configuration Connection Agreement. The Configuration CA also connects the legacy Configuration container to the Recipient Policies container in Active Directory so that the ADC can update addressing policies. This is how Exchange 2003 finds out about the SMTP, X.400, and other proxy addresses currently used by legacy Exchange.

Configuration CA Endpoints

During your migration from legacy Exchange to Exchange 2003, you'll be decommissioning legacy servers. At some point, a given site might not have any remaining legacy servers, but the Exchange 5.x servers in other sites must still replicate the legacy Configuration partition so they can calculate message routing.

You could leave a legacy server in each site until you're just about ready to finish your migration, but to help smooth the transition, an Exchange 2003 server pretends to be a legacy Exchange server so it can replicate the Configuration container to the other legacy servers. That's the job of the SRS. An upcoming section in this chapter titled "Site Replication Service Configuration" details the operation of the SRS.

Public Folder Connection Agreements

Legacy Exchange public folders also act like standard recipients in that they can receive mail and belong to distribution lists. Active Directory represents mail-enabled public folders with a special object called Public Folder.

A Public Folder Connection Agreement in the ADC populates Active Directory with one Public Folder object for each public folder in the Public Folder Hierarchy. If you have 10,000 public folders in legacy Exchange, you'll end up with 10,000 Public Folder objects in Active Directory.

Public Folder CAs created by the Connection Agreement Wizard resemble Recipient CAs. Here are the differences:

  • Both CA types define a two-way connection agreement with an Exchange server as the endpoint on one side of the CA and Active Directory on the other side.

  • Both CA types limit the CA so that only the Windows side acts as a Primary CA.

  • Both CA types have a default schedule of Always.

Their primary difference lies in the type of object included in the search criteria. A Public Folder CA searches only for objects of the Public Folder class in Active Directory and for public folders in legacy Exchange.

The target container in Active Directory is also different. A Public Folder CA points at the Microsoft Exchange System Objects container, as shown in Figure 12.38.

12fig38.gifFigure 12.38 Public Folder Connection Agreement properties showing that the destination is the Microsoft Exchange System Objects container so that Public Folder objects can be created to correspond with mail-enabled MAPI public folders.legacy Exchange serversmigration to Exchange 2003CA propertiesmigration from legacy ExchangeCA propertiespublic foldersCAs (Connection Agreements)propertiespublic folder CAsPublic Folder Connection Agreements

When the ADC runs the Public Folder CA for the first time, the Microsoft Exchange System Objects container fills with objects representing public folders. Figure 12.39 shows the Microsoft Exchange System Objects container after the initial replication. (Select View | Advanced view in the console to see the container.)

12fig39.jpgFigure 12.39 Active Directory Users and Computers console showing Public Folder objects created by Public Folder CA.legacy Exchange serversmigration to Exchange 2003CA propertiesmigration from legacy ExchangeCA propertiespublic foldersCAs (Connection Agreements)propertiespublic folder CAsPublic Folder Connection Agreements

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