Planning Communication Topologies

In computer networking, the pattern of connections among devices is called the communication topology. A communication topology defines the relationship that exists among the replicas of the database, along with the logic that determines how synchronization occurs among those replicas.

An important part of implementing replication in your application is planning the appropriate communication topology for synchronizing data and schema changes. Topology is important because it determines:

• How long it takes for changes to get from a Publisher to a Subscriber.
• Whether the failure of a single update prevents other Subscribers from being updated.
• The order in which updated information arrives at a Subscriber, which can affect analysis and reporting.

In its simplest topology, Microsoft® SQL Server™ replication uses a single Publisher and Distributor on the same server and a single Subscriber on a separate server. In most organizations, however, there may be dozens of Publishers, dozens of Distributors, and hundreds (or even thousands) of Subscribers.

It is important to note that the communication topology is not limited to the physical connections between servers; it also includes data paths between replicas. Many subscriptions can exist on a single server, incorporating a complicated communication topology.