A question came up in a newsgroup recently about all of the different objects with schedules on them and wanting to know what they are. It’s a great question and I think once you know the answer you’ll feel like you always knew the answer. I love Active Directory – yes, to the point that I would consider marrying it – and this concept took longer than normal to permeate my thick skull. I want to take you through the different objects, their schedules, and their source.
Sites and Site Links
If we let Active Directory work for us, typically all we need to do to get our replication topology built is to define sites and site links. Sites are intended to represent a logical instance of well-connected physical locations. Site links are intended to represent the logical connectivity paths between sites. It’s often been said that site links should mirror your network topology but I would caution against this. That works sometimes but it’s not always effective. For instance, if you have an MPLS cloud that all of your sites connect into, it’s still probably not a good idea to create a site link which includes all of your sites.
Instead, when you create site links, consider this your opportunity to tell Active Directory what you want it to do. Tell it what sites you want to allow to talk with each other and under what conditions. Among the many options, both basic and advanced, that can be configured on the site link, this is the first place that we come across a schedule.
Site links actually present an interesting condition because Active Directory never shows the final replication schedule. Instead it shows the things that make up the replication schedule: the availability schedule and a replication interval.
Availability Schedule
The schedule on a site link, which is visible by selecting Change Schedule on the Properties of the site link, is an availability schedule. Think about it like the hours that a store is open