ConfMgr SP1 – WSUS Upstream Server
One of the useful things that Configuration Manager 2012 SP1 has brought is allowing usage of WSUS as an upstream server.
Paragraph from http://technet.microsoft.com/en-us/library/jj591552.aspx
At the top-level Configuration Manager site, you can now specify an existing WSUS server as the upstream synchronization source location. During synchronization, the site connects to this location to synchronize software updates. For example, if you have an existing WSUS server that is not part of the Configuration Manager hierarchy, you can specify the existing WSUS server to synchronize software updates.