As we mentioned in Chapter 5, there are two aspects to replication:
How data gets replicated around an existing network of links between DCs
How the Knowledge Consistency Checker generates and maintains the replication links between servers, both intrasite and intersite
We covered the former in Chapter 5, and we'll cover the latter here, leading to an explanation of how to properly design a representation of your organization's network infrastructure within Active Directory.
Two distinct types of replication links exist with Active Directory sites: intrasite (within sites) and intersite (between sites). An Active Directory service known as the Knowledge Consistency Checker (KCC) is responsible for automatically generating the replication links between intrasite DCs. The KCC will create intersite links automatically for you as well, but only when an administrator has specified that two sites should be connected. Every aspect of the KCC and the links that are created is configurable, so you can manipulate what has been automatically created and what will be automatically created via manipulation of the various options. You can even disable the KCC if you wish and manually create all links.
Note that there is a large distinction between the KCC (the process that runs every 15 minutes and creates the replication topology) and the replication process itself. The KCC is not involved in the regular work of replicating ...