WSUS server modes

https://technet.microsoft.com/en-us/library/cc720448(v=ws.10).aspx

There are two ways to link WSUS servers together:

Autonomous mode: An upstream WSUS server shares updates with its downstream server or servers during synchronization, but not update approval status or computer group information. Downstream WSUS servers must be administered separately. Autonomous servers can also synchronize updates for a set of languages that is a subset of the set synchronized by their upstream server.

Replica mode: An upstream WSUS server shares updates, approval status, and computer groups with its downstream server or servers. Downstream replica servers inherit update approvals and cannot be administered apart from their upstream WSUS server.