After installing the latest update for Windows 10, some have been wondering why internal network traffic has increased and traffic to the WSUS server has decreased. Michael Niehaus took the Microsoft blogs yesterday to explain that, in Windows 10 Anniversary Update, Deliver Optimization to work with peer caching has been enabled by default.
This option enables the WSUS client to pull from other Windows 10 PCs that have already downloaded and cached the updates Instead of always going directly to the WSUS server every time.
This method can be altered with a GPO setting and Michael gives the details here: Using WSUS with Windows 10 1607?
Delivery Optimization is a piece of the Windows Update for Business features that Microsoft has been slowly evolving with every new Windows 10 update.