The Active directory is a database. It designed to handle a large number of read and search operations and a smaller number of changes and updates. Active directory replication is to ensure that the information stored on all domain controllers within a domain synchronized. The domains and domain controllers are multiple communication paths connect them. The method of transferring updates and other changes to the active directory involves all the server communicating directly with each other as soon as the changes occurs.
This replication takes places high requirements on the interwork bandwidth and is inefficient for many network environments that use slower and more costly WAN links. All the environment update at the same time, simultaneous updating could cause the network connection at the core of the network and decrease the performance of the entire WAN.
The active directory can automatically determine the best methods for performing replication operations. The sites takes into the account an organization network infrastructure and active directory uses these site to determine the method for synchronizing information between domain controllers. The system administrator can make their physical network design map to active directory objects. Based on the creation and configuration of these objects, the active directory service can manage replication traffic in an efficient way.
Whenever changes made in active directory database on domain controller, the change is given an update sequence number. The domain controller can propagate these changes to other domain controllers based on the replication settings.
In windows active directory the replication are of two types they are
- Intrasite Replication
- Intersite Replication
Intrasite Replication
Intrasite replication refers to the synchronization of active directory information between domain controllers that are located in the same site. The communication between domain controllers occur using the Remote Procedure Call (RPC) Protocol. These machines are usually well connected with the high speed LAN.
Intersite Replication
Intersite replication refers to the synchronization of active directory information between domain controller in the different sites. Usually that there is a WAN or other type of low speed network connection between the various machines. In this there are two different protocols may be used to transfer information between sites. They are
- RPC over IP
- Simple Mail Transfer Protocol (SMTP)
RPC over IP
Connection between two or more domain controllers in different sites and let you transfer the active directory information. RPC over IP was originally designed for slower WAN in which packet loss and corruption may occur often. As it is a good choice for low quality connections involved in the intersite replication.
Simple Mail Transfer Protocol (SMTP)
It was designed to use a store-and-forward mechanism through which a server receives a copy of message, record it to disk, and then attempts to forward it to another email server. If the destination server is unavailable, it holds the message and attempts to resend it at periodic intervals.
