As mentioned previously, intra-site replication is initiated based on change notification. However, inter-site replication, by default, is not. Instead, replication occurs between sites based on the schedule set on site links and the frequency at which replication will occur. This serves to give administrators the ability to control replication between locations that might not have connections with a lot of available bandwidth.
Essentially, three items control the replication process between sites: the cost assigned to the site link, the schedule, and the interval associated with the site link.