AD Replication Process Overview
So what's the big deal with AD Replication? I mean it's obvious that your infrastructure has multiple Domain Controllers and you want to make sure that Active Directory talks to each other directly or indirectly and keep each other up to date. We came up with Replication concept. Now it's important that Domain controller talk to right domain controller, I mean there should not be any confusion, everyone should be aware who is sending update and receiving updates from whom. So we came up with KCC concept ( Knowledge Consistency Checker - it helps to design the replication topology automatically)Now too much talking between AD Servers are also not good, each site is connected using very costly WAN link and I am sure any company don't want any useless replication happening via these costly links. So we came up with concepts like Site Link Cost, Replication Schedule.Trust me AD Replication is a huge topic. This article one pretty much explains basic replication concept between 2 DC's.Active Directory (AD) is a multi-master directory, meaning each directory services server—referred to as a domain controller—contains a fully readable and writeable copy of the directoryservices database. Because all domain controllers can accept changes to the database, some method is needed to replicate those changes to other domain controllers, ensuring a consistentdatabase across all domain controllers. This scheme is referred to as AD replication.AD replication can be broken down into four basic operational components:
It is a list of servers that participate in replication and the servers with which they replicate. Referred to as a replication topology, this list is generated by a special AD component called the Knowledge Consistency Checker (KCC).Checking replication Topology - http://technet.microsoft.com/en-us/library/cc739234(v=ws.10).aspx
It is the information that is being replicated. AD uses attribute-based replication and versioning to determine which information has changed and requires replication.http://windowsitpro.com/active-directory/active-directory-replication-depth
It is a schedule that determines when replication will occur. Separate schedules exist for replication within an AD site and for each link connecting different sites.Managing Replication between sites- http://technet.microsoft.com/en-us/library/cc961783.aspx
It defines how the replicated data is physically transported across the network.
To know more about AD replication please refer to below articles:
Troubleshooting Replication: http://technet.microsoft.com/en-us/library/cc755349(WS.10).aspx#BKMK_1