Active directory site replication occurs by using a KCC, Which is in avery site and creates a repliation topolgy to replicate the data from one domain to other domain and it uses RPC protocol to replicate data.
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Santosh Rawat
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Active Directory is called active bacause it is actively updating it's data through replication from differnt sites and other domain controllers with in the network
every three hours.
Bridgehead servers are used in Active Directory replication to reduce network traffic by serving as intermediaries between sites, thus minimizing the number of replication connections needed. They also help control the flow of replication data by efficiently routing updates between domain controllers in different sites. This ensures that changes to the directory are replicated efficiently across the network.
The four types of Active Directory container objects are Organizational Units (OUs), domains, sites, and the built-in container. Organizational Units are used to organize users, groups, and devices for management and delegation of permissions. Domains represent a logical group of objects within the directory, while sites are used to manage replication and network topology. The built-in container holds default groups and accounts that are created with Active Directory.
Active Directory Sites and Services
The Knowledge Consistency Checker (KCC) is a dynamic-link library (DLL) that runs as a distributed application on every domain controller. The KCC on each domain controller modifies data in its local instance of the directory in response to forest-wide changes, which are made known to the KCC by changes to data in the configuration directory partition. The KCC generates and maintains the replication topology for replication within sites and between sites by converting KCC-defined and administrator-defined (if any) connection objects into a configuration that is understood by the directory replication engine.
The Active Directory administrative tools can only be used from a computer with access to a domain. The following Active Directory administrative tools are available on the Administrative Tools menu: Active Directory Users and Computers (dsa.msc) Active Directory Domains and Trusts (domain.msc) Active Directory Sites and Services (dssite.msc)
Your question it not clear so .....Sites in Active Directory are the physical network structure of Active Directory based on subnet or subnets. Each site in Active Directory resembles well connected network. It is sometimes referred as physical structure of AD. Depending upon the locations and connection quality sites are created which include a domain or domains.Creating these sites lets you control replication traffic over WAN links. In a way Sites help define the AD's replication topology.
A chain of site links in Active Directory defines how domain controllers in different sites communicate with each other. These site links are established between sites and specify the replication topology, including the cost and frequency of replication traffic. They ensure that changes within the directory are efficiently synchronized across geographically dispersed locations. Properly configured site links optimize network bandwidth and enhance the overall performance of directory services.
every 3 hours
One or more well-connected (highly reliable and fast) TCP/IP subnets. A site allows administrators to configure Active Directory access and replication topology to take advantage of the physical network. B: A Site object in Active Directory represents a physical geographic location that hosts networks. Sites contain objects called Subnets.[3] Sites can be used to Assign Group Policy Objects, facilitate the discovery of resources, manage active directory replication, and manage network link traffic. Sites can be linked to other Sites. Site-linked objects may be assigned a cost value that represents the speed, reliability, availability, or other real property of a physical resource. Site Links may also be assigned a schedule. Source: http://en.wikipedia.org/wiki/Active_Directory_Site#Sites