Chapter 3

This chapter covered how to work with AD sites. Replication sites are a means by which admins can control replication traffic between AD domain controllers, both when the controllers are on the same server (intrasite replication) and on separate servers (intersite replication). Intersite replication communications are done using a compressed signal, whereas intrasite traffic isn't, in order to conserve bandwidth.After giving this lowdown, the book went through how the replication process worked. Replication occurs whenever an object is added to a domain, the value of an attribute changes or the name of an object changes. Whenever changes are made to an AD domain controller, the normal thing is for the AD controller to communicate changes to each other (replication). If changes take place on more than one domain controller, the replication goes to a bridgehead server which then makes the decision, based on several criteria (timestamp, etc) as to which change is replicated and then transmits this to all other domain controllers. Wit intrasite replication the knowledge consistency checker (KCC) to to map network topology between domain controllers. Intranetwork replication follows a rule that says no replication traffic should have to go more than 3 hops to hit an AD domain controller that can originate a change to the AD database in order to minimize the time required to change all the domain controllers' information. KCC can be configured manually, though doing this removes its ability to automate topology mapping. Intersite replication uses site links through which it communicates changes in AD domain controllers for a multisite network. It uses the intersite topology generator (ISTG) which chooses a bridgehead server and maps the network between sites. AD can use either RPC over IP or SMTP when senting replication traffic to AD domain controllers. AD occasionally has to deal with errors in replication, which are logged in event viewer. KCC can be forced to run under some of these circumstances in order to complete replication. AD replication is monitored by Dcdiag and Repadmin tools included in AD.