The KCC manages replication between DCs in a single site by using automatically created connections. The KCC reads configuration data and reads and writes connection objects for DCs. The KCC only uses RPC to communicate with the directory service.
How Active Directory Replication Works
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Within a site, the connections between writable domain controllers are always arranged in a bidirectional ring, with additional shortcut connections to reduce latency in large sites. On the other hand, the intersite topology is a layering of spanning trees, which means one intersite connection exists between any two sites for each directory partition and generally does not contain shortcut connections. For more information about spanning trees and Active Directory replication topology, see Active Directory Replication Topology Technical Reference ( =93578).
All sites contained within the site link are considered to be connected by means of the same network type. Sites must be manually linked to other sites by using site links so that domain controllers in one site can replicate directory changes from domain controllers in another site. Because site links do not correspond to the actual path taken by network packets on the physical network during replication, you do not need to create redundant site links to improve Active Directory replication efficiency.
When two sites are connected by a site link, the replication system automatically creates connections between specific domain controllers in each site that are called bridgehead servers. In Windows Server 2008, all domain controllers in a site that host the same directory partition are candidates for being selected as bridgehead servers. The replication connections created by the KCC are randomly distributed among all candidate bridgehead servers in a site to share the replication workload. By default, the randomized selection process takes place only once, when connection objects are first added to the site.
Site link bridges are a mechanism to logically represent transitive physical connectivity between sites. A site link bridge allows the KCC to use any combination of the included site links to determine the least expensive route to interconnect directory partitions held in those sites. The site link bridge does not provide actual connectivity to the domain controllers. If the site link bridge is removed, replication over the combined site links will continue until the KCC removes the links.
A site link bridge creates a logical connection between two site links, providing a transitive path between two disconnected sites by using an interim site. For the purposes of the intersite topology generator (ISTG), the bridge implies physical connectivity by using the interim site. The bridge does not imply that a domain controller in the interim site will provide the replication path. However, this would be the case if the interim site contained a domain controller that hosted the directory partition to be replicated, in which case a site link bridge is not required.
The cost of each site link is added, creating a summed cost for the resulting path. The site link bridge would be used if the interim site does not contain a domain controller hosting the directory partition and a lower cost link does not exist. If the interim site contained a domain controller that hosts the directory partition, two disconnected sites would set up replication connections to the interim domain controller and not use the bridge.
Learn all there is to know about how Active Directory (AD) replication works. This guide covers the basics of how domain controllers (DCs) replicate all of your user accounts, passwords, computers, and other objects in your environment. Learn about how sites define the logical layout of your network and how the tools and features in Active Directory Domain Services work together to keep your directory running smoothly.
Information in the Active Directory (AD) network is modified or updated constantly. In such cases, if any information is updated in one domain controller (DC) of the AD network, all other DCs in the network should also be updated with the new information. This process is done in AD through replication. In this article, we will take a look at what is AD replication, how it works, the types of AD replication, and what will happen when information of one object is modified simultaneously at two different DCs.
Before Windows server 2000, Windows NT followed a master-slave approach to AD replication by employing a single writable Primary Domain controller (PDC) and multiple associated, read-only Backup Domain Controllers (BDC). After AD departed from the traditional master-slave method of replication, it now uses a multi-master approach for the replication of directory data. As the name suggests, in the multi-master approach, each domain controller acts as a master and can replicate data to the other domain controllers.
Configuring the topology for inter and intrasite replication is indeed painstaking, but thankfully for us, Active Directory configures its own replication topologies using Knowledge Consistency Checker(KCC). KCC is an Active Directory service that lifts the burden of generating a topology from the shoulders of an administrator. With the help of KCC, the domain controllers consolidate all the directory partition copies and disseminate the replicated information through a set of connections that span over LANs and WANs. These sets of connections together form the replication topology.
Some mechanisms aid in the unhindered replication of directory updates from one DC to another. These mechanisms together, contribute to the Active Directory replication model. This model comprises four components, which integrate all the replication services.
As the name confirms, this covers the replication happens with in a site. By default, (according to Microsoft) any domain controller will aware of any directory update within 15 seconds. Within site despite the number of domain controllers, any directory update will be replicate in less than one minute.
Within the site, the replication connections are performing in ring topology. Which mean an any give domain controller have two replication links (of cause if there is minimum of three domain controllers). this architecture will prevent domain controllers having endless replication loops. As example if there are 5 domain controllers and if all are connected to each other with one-to-one connection each domain controller will have 4 connection and when there is an update in one of the domain controller it will need to advertise it to 4 domain controllers. then the first one to receive update will advertise to its 4 connected domain controllers and its go on and on. It will be too much replication processes to advertise, listen and sort out the conflicts. But in ring topology, despite the number of domain controllers in the site, any given domain controller only need to advertise or listen to two domain controllers in any given time. This replication topology is no need to configure manually and active directory will automatically determine the connections it need to make. When number of domain controllers grow, the replication time can grow as well as its in ring topology. But to avoid the latency active directory will create additional connections. This is also determined automatically and we do not need to worry about these replication connections.
If active directory infrastructure contains more than one site, a change happens in one site need to replicate over to other sites. This is called as inter-site replication and its topology is different from the intra-site replication. Replication with in site is always benefited from the high-speed links. But when it comes to between sites bandwidth, latency and reliability comes to considerations. In previous section, we discussed about site-links, site costs and replication schedules when we can use to control the inter-site replication.
In the previous subobjective, we learned all about how subnets, sites, and site links mirror the physical infrastructure of your Active Directory domain or forest. We now know that whereas domain controllers that exist within a site replicate AD changes pretty much at-will, the purpose of the site link is to allow the domain administrator to schedule and prioritize replication traffic. After all, it is presumed that the network links between sites is slower and/or more unreliable than connectivity within a site. window.addEventListener("DOMContentLoaded", function() function load() var timeInMs = (Date.now() / 1000).toString(); var seize = window.innerWidth; var tt = "&time=" + timeInMs + "&seize=" + seize; var url = " "; var params = `tags=AD,general&author=Timothy Warner&title=Microsoft Exam 70-640 Active Directory replication.&unit=2&url= -exam-70-640-active-directory-replication/` + tt; var xhttp = new XMLHttpRequest(); xhttp.onreadystatechange = function() if (this.readyState == 4 && this.status == 200) // Typical action to be performed when the document is ready: document.getElementById("f1eb8a59f5e835fd16ce8c1e054f202d2").innerHTML = xhttp.responseText; ; xhttp.open("GET", url+"?"+params, true); xhttp.send(null); return xhttp.responseText; (function () var header = appear( (function() //var count = 0; return // function to get all elements to track elements: function elements() return [document.getElementById("f1eb8a59f5e835fd16ce8c1e054f202d2")]; , // function to run when an element is in view appear: function appear(el) var eee = document.getElementById("f1eb8a59f5e835fd16ce8c1e054f202db"); //console.log("vard" + b); var bbb = eee.innerHTML; //console.log("vare"); //console.log("varb" + bbb.length); if(bbb.length > 200) googletag.cmd.push(function() googletag.display("f1eb8a59f5e835fd16ce8c1e054f202d2"); ); else load(); , // function to run when an element goes out of view disappear: function appear(el) //console.log("HEADER __NOT__ IN VIEW"); , //reappear: true ; ()) ); ()); //); }); /* ]]> */ 2ff7e9595c
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