Active Directory replication continued ...
When replicating a naming context, a domain controller maintains a high watermark table to pick up where it left off. . There is one table for every naming context which totals three if we include schema, configuration and domain NCs. Each table stores the highest USN of the updates so that only new information is requested.
This is different from the Up-to-dateness vector which is another table that the DC maintains to assist in efficient replication of a naming context by removing redundancies in replication and endless replication loops. The two tables can be used together to improve the efficiency in replication.
By filtering out the same changes from multiple sources, only the updates that have not been made yet are done. This is called propagation dampening. Thus we have seen that the Active Directory is split into separate naming contexts each of which is replicated independently and that within each naming context, a variety of metadata is held. Update entries consist of originating-DSA-GUID,originating-USN and a timestamp indicating the last successful replication with the originating domain controller. These values are updated only during a replication cycle.
As an example of replication, we take the following example from the book :Step 1) a user is created on DC A Step2) That object is replicated to DC B. Step 3) DC B is subsequently modified and Step 4) the new changes to that object are replicated back to DC A. The Active Directory database transaction representing step 1 consists of a USN and the timestamp. The replication of the originating write to a DC B allocates a different USN and the users USNCreated and USNChanged attributes are updated. In Step 3) the password change for the user on DC B also modifies this USNChanged attribute for the user. In addition the password attribute is modified and the corresponding USN and timestamp updated. The step 4 is similar to step 2. A change transaction is issued and the attributes updated. To look at how the replication occurs, we look at the following five steps : Step 1) Replication with a partner is initiated Step 2) the partner works out what updates to send. Step 3) The partner sends the updates to the initiating server. Step 4) The initiating server processes the updates and Step 5) The initiating server checks whether it is up to date.
When replicating a naming context, a domain controller maintains a high watermark table to pick up where it left off. . There is one table for every naming context which totals three if we include schema, configuration and domain NCs. Each table stores the highest USN of the updates so that only new information is requested.
This is different from the Up-to-dateness vector which is another table that the DC maintains to assist in efficient replication of a naming context by removing redundancies in replication and endless replication loops. The two tables can be used together to improve the efficiency in replication.
By filtering out the same changes from multiple sources, only the updates that have not been made yet are done. This is called propagation dampening. Thus we have seen that the Active Directory is split into separate naming contexts each of which is replicated independently and that within each naming context, a variety of metadata is held. Update entries consist of originating-DSA-GUID,originating-USN and a timestamp indicating the last successful replication with the originating domain controller. These values are updated only during a replication cycle.
As an example of replication, we take the following example from the book :Step 1) a user is created on DC A Step2) That object is replicated to DC B. Step 3) DC B is subsequently modified and Step 4) the new changes to that object are replicated back to DC A. The Active Directory database transaction representing step 1 consists of a USN and the timestamp. The replication of the originating write to a DC B allocates a different USN and the users USNCreated and USNChanged attributes are updated. In Step 3) the password change for the user on DC B also modifies this USNChanged attribute for the user. In addition the password attribute is modified and the corresponding USN and timestamp updated. The step 4 is similar to step 2. A change transaction is issued and the attributes updated. To look at how the replication occurs, we look at the following five steps : Step 1) Replication with a partner is initiated Step 2) the partner works out what updates to send. Step 3) The partner sends the updates to the initiating server. Step 4) The initiating server processes the updates and Step 5) The initiating server checks whether it is up to date.
No comments:
Post a Comment