Answer: In Active Directory all sites are connected by Inter-Site Transports links that allows us to replicate AD traffic from site to site.
In large organizations the cost and the capacity of the links are different from site to site and this is where Active Directory allows us to control which link will be use more often between each site based on capacity and cost.
This article will show you how to create and configure a new site link.
To Create a new site link follow the steps below:
Open Active Directory Sites And Services -> Go to Inter-Site Transports -> IP
Right Click on IP -> Click on New Site Link
Name the Site Link and select the Sites that will be part of the link (you can change this later)
To configure the cost and replication interval, Right Click on the new link and click on properties
In the site Link Properties, You can change the Link Cost, Replication interval and schedule.
You can also add and remove sites that will use the link.